CRISPR-Cas Systems in Targeted Drug Delivery and Gene Therapy: An Emerging Approach to Precision Medicine

Mohd Uzair, Shabnam Ain^*, Qurratul Ain, Babita Kumar, Vipin Kumar,                   Sneha Pandey, Ajeet and Cutee

Sanskar College of Pharmacy and Research, Ghaziabad, Uttar Pradesh.

 

Correspondence: shabnam.ain@sanskar.org; Tel.: +919310807567

DOI: https://doi.org/10.71431/IJRPAS.2026.5206

 

Article Information		Abstract
Review Article Received: 24/02/2026 Accepted: 02/03/2026 Published:06/03/2026   Keywords CRISPR-Cas systems, genome editing, gene therapy, targeted drug delivery, personalized medicine, nanotechnology		The CRISPR-Cas system has revolutionized genetic engineering by offering precise genome editing with unparalleled accuracy. Its integration into targeted drug delivery and gene therapy represents a transformative approach for treating genetic disorders, cancers, and infectious diseases. Originally identified as part of a bacterial immune defense mechanism, CRISPR-Cas has evolved into a versatile tool for site-specific genome editing, enabling correction of disease-causing mutations with minimal off-target effects. In drug delivery, CRISPR-based platforms are being engineered to direct therapeutic agents specifically to diseased tissues or cells, thereby reducing systemic toxicity while enhancing efficacy. Advanced carriers such as nanoparticles, liposomes, and viral and non-viral vectors are under exploration to improve the efficiency and precision of CRISPR component delivery. In the realm of gene therapy, CRISPR technologies show significant promise for treating conditions such as sickle cell anemia, cystic fibrosis, muscular dystrophy, and various malignancies by rewriting defective genes or introducing protective modifications within the genome. Despite this promise, challenges such as delivery limitations, immunogenicity, and ethical concerns, particularly regarding germline editing, remain critical. Regulatory frameworks are evolving to ensure safe clinical translation. Overall, crispr-cas technologies are expected to play a pivotal role in advancing personalized medicine, offering hope for conditions once considered untreatable. This review highlights recent breakthroughs, evaluates delivery strategies, and discusses future directions toward safe and effective clinical application

 

INTRODUCTION

Over the past decade, advances in genetic engineering have catalyzed a paradigm shift in the treatment of a wide array of diseases [1, 2]. Among the most transformative of these technologies is the CRISPR-Cas (Clustered Regularly Interspaced Short Palindromic Repeats – CRISPR-associated) system, a prokaryotic immune mechanism that has been adapted into a powerful tool for targeted genome editing [27, 33]. Its remarkable specificity, programmability, and simplicity have enabled researchers to edit DNA with unprecedented precision and efficiency [4, 33]. As such, CRISPR-Cas systems have rapidly emerged as a cornerstone technology in molecular biology, biotechnology, and translational medicine [5, 34].

The application of CRISPR technology is particularly promising in the fields of targeted drug delivery and gene therapy [6, 8]. Conventional therapeutic approaches often suffer from issues such as non-specific distribution, systemic toxicity, and suboptimal efficacy [9, 13]. Gene therapy, which seeks to correct or replace defective genes at the molecular level, has gained substantial momentum; however, its success heavily relies on the precise and efficient delivery of therapeutic payloads into specific cells or tissues [17, 18, 31]. This is where CRISPR systems offer a distinct advantage by enabling gene-level interventions that are both site-specific and potentially curative [11, 19].

In parallel, the integration of CRISPR tools with advanced drug delivery systems, particularly those utilizing nanotechnology, has further enhanced the scope and safety of these interventions [8, 17]. Nanoparticles, liposomes, dendrimers, and other engineered carriers have shown significant promise in facilitating the targeted transport of CRISPR components, thereby overcoming major biological barriers such as enzymatic degradation, immune clearance, and poor cellular uptake [12, 22, 35]. The synergy between gene editing and delivery technologies holds the potential to revolutionize the therapeutic landscape for genetic disorders, cancers, and infectious diseases [6, 14, 38].

Moreover, the modular nature of CRISPR systems allows them to be tailored for various gene therapy strategies—from gene knockouts and corrections to epigenetic modulation and RNA editing [23, 24]. With the advent of next-generation CRISPR variants such as Cas12, Cas13, and base editors, the functional capabilities have further expanded, offering greater versatility for clinical applications [26], 36]. Despite these advancements, challenges such as off-target effects, immunogenicity, ethical considerations, and delivery efficiency remain significant hurdles that must be addressed before widespread clinical adoption can be realized [7, 20, 21, 39].

This review article aims to provide a comprehensive understanding of CRISPR-Cas systems, with a specific emphasis on their role in targeted drug delivery and gene therapy [5, 6]. It explores the underlying mechanisms, current advancements, delivery strategies, therapeutic applications, and future prospects, while also discussing the associated challenges and bioethical concerns [9, 28, 32]. By illuminating the intersection of genome editing and nanomedicine, this work contributes to the growing body of knowledge guiding the development of next-generation precision therapeutics [10, 17, 34].

Background and significance

The ability to manipulate genetic material with precision has long been a goal in biomedical research [1, 2]. The emergence of CRISPR-Cas systems has revolutionized genome editing by offering a fast, cost-effective, and versatile method to introduce targeted genetic modifications [3, 4]. Originating from the adaptive immune defense mechanisms of bacteria and archaea, the CRISPR-Cas system uses RNA-guided nucleases to identify and cleave specific DNA sequences [27, 33]. This capability has opened new possibilities in disease modeling, gene therapy, functional genomics, and synthetic biology [5, 23, 24].

Genetic diseases, cancers, and chronic illnesses such as viral infections often require targeted therapeutic interventions [6, 13]. Traditional pharmacological treatments typically fail to address the root cause of these conditions—namely, the underlying genetic abnormalities [29, 30]. In contrast, CRISPR-based gene editing technologies aim to correct the genetic blueprint itself, thereby offering curative potential rather than symptomatic relief. This transformative approach has positioned CRISPR-Cas systems at the forefront of precision medicine [25, 26, 31].

The need for targeted drug delivery

Despite the enormous therapeutic promise of CRISPR, effective and safe delivery of CRISPR components (such as Cas nucleases and guide RNAs) into target cells remains a significant challenge [6, 9, 13]. Conventional delivery methods often result in low transfection efficiency, off-target effects, and immune responses [14, 17, 31]. Moreover, systemic administration without targeting can lead to biodistribution into non-diseased tissues, raising safety concerns [19, 20].

To overcome these barriers, the integration of targeted drug delivery systems with CRISPR-Cas technology has gained considerable attention [8, 12]. Engineered nanocarriers such as lipid nanoparticles, polymeric nanoparticles, dendrimers, and viral vectors are being explored to facilitate the controlled, tissue-specific delivery of CRISPR machinery [10, 18, 22]. These systems can enhance cellular uptake, protect the cargo from degradation, and reduce immunogenicity—ultimately improving therapeutic outcomes [16, 32, 35].

Crispr-cas systems in gene therapy

Gene therapy, once plagued by delivery and specificity issues, is now being revitalized by CRISPR technology [6, 15]. The CRISPR-Cas9 system enables programmable DNA cleavage, allowing for gene knockout, knock-in, or correction of mutations [1, 27, 33]. More recently, base editing and prime editing tools have further expanded the editing toolkit, enabling precise nucleotide changes without inducing double-strand breaks [26, 36].

In diseases such as sickle cell anemia, β-thalassemia, Duchenne muscular dystrophy, and certain forms of cancer, CRISPR-mediated gene therapy has already demonstrated promising preclinical and clinical outcomes [16, 19, 29]. Moreover, CRISPR-Cas systems are being developed to target viral genomes such as those of HIV, HPV, and hepatitis B, offering a novel antiviral strategy [28, 30, 38].

Scope and objectives of the review

This review aims to explore the current landscape of CRISPR-Cas systems in the context of targeted drug delivery and gene therapy [5, 6]. It begins with an overview of the CRISPR-Cas mechanism and its classification, followed by a detailed discussion on strategies for efficient in vivo delivery [7, 8, 9]. The review then examines clinical and experimental applications in genetic disorders and cancer treatment, the integration of nanocarrier systems, and the latest innovations in delivery technologies [10, 17, 22].

CRISPR-CAS SYSTEM: AN OVERVIEW

Historical development and origin

The CRISPR-Cas system was first identified in Escherichia coli in the late 1980s, where it was initially characterized as an array of repetitive DNA sequences [1, 27]. However, it was not until 2005 that scientists recognized these sequences as part of an adaptive immune defense mechanism in bacteria and archaea [2, 4, 33]. This system provides acquired resistance against invading viruses (bacteriophages) by incorporating short segments of viral DNA, known as spacers, into the host genome [5, 23]. These spacers are then used to produce CRISPR RNAs (crRNAs), which guide Cas (CRISPR-associated) proteins to recognize and cleave foreign nucleic acids during subsequent infections [27, 29, 30].

Classification of crispr-cas systems

CRISPR systems are broadly divided into two main classes based on their structural and functional components i.e., Class1-Utilizes multi-subunit protein complexes for interference (e.g., Cas3, Cas5)  [1, 27], Class2-Employs a single, multidomain effector protein for DNA cleavage, most notably Cas9[2, 8, 23]. Within these classes, there are further subdivisions into six types (Type I–VI) and multiple subtypes. Among these, Type II CRISPR-Cas9 from Streptococcus pyogenes has become the most widely used system in genome editing due to its simplicity and versatility [4, 7, 33].

Structure and component

A typical CRISPR-Cas9 editing complex consists of Cas9 protein: A nuclease enzyme responsible for creating double-stranded breaks (DSBs) in DNA[27, 33], Guide RNA (gRNA): A synthetic RNA molecule combining crRNA and tracrRNA, which directs Cas9 to the target sequence[24, 29], Protospacer Adjacent Motif (PAM): A short DNA sequence adjacent to the target site that is essential for Cas9 binding and cleavage. The most common PAM for SpCas9 is 5’-NGG-3’ [33, 36].

Mechanism of action

The CRISPR-Cas9 system operates in a three-step process which are Recognition: The guide RNA base-pairs with the complementary target DNA sequence[23, 24], Binding: Cas9 binds to the PAM site and unwinds the local DNA[24, 33], Cleavage: The nuclease domains of Cas9 (RuvC and HNH) create a double-stranded break, which is subsequently repaired by the host’s cellular machinery via Non-Homologous End Joining (NHEJ): Error-prone, may result in gene knockouts[5, 26], Homology-Directed Repair (HDR): Error-free, used for precise gene editing with donor templates[7, 25].

Emerging crispr variants and tools

In addition to the canonical Cas9 system, new CRISPR tools have been developed with enhanced functionality are Cas12a (Cpf1): Creates staggered DSBs and does not require tracrRNA, expanding targetable sequences[29, 36], Cas13: Targets RNA instead of DNA, useful for post-transcriptional regulation[26, 37], Base Editors: Enable nucleotide substitution without inducing DSBs[33, 36], Prime Editing: Allows precise insertion, deletion, or replacement of nucleotides without DSBs or donor templates[26, 32].

These advances broaden the spectrum of gene manipulation and increase safety, specificity, and therapeutic relevance.

Relevance to human therapeutics

The modular and programmable nature of CRISPR-Cas systems makes them ideal candidates for correcting disease-causing mutations [15, 29, 30]. The ability to target virtually any gene in the human genome holds enormous promise for personalized medicine, functional genomics, synthetic biology, and next-generation gene therapy [23, 24, 25]. Moreover, coupling CRISPR with precision delivery strategies enhances its clinical feasibility, forming the foundation of this review [6, 10, 17, 22].

MECHANISM OF CRISPR-CAS IN GENE EDITING AND REGULATION

Introduction to gene editing mechanics

CRISPR-Cas systems function as molecular scissors capable of altering genomic sequences with high specificity [1, 2, 27]. The core of this mechanism lies in the targeted cleavage of DNA followed by the activation of the cell's innate repair pathways [4, 33]. By leveraging these natural DNA repair systems, CRISPR enables the insertion, deletion, or correction of specific genetic sequences [26, 27]. The precision of editing is largely dependent on the design of the guide RNA (gRNA) and the fidelity of the Cas enzyme employed [7, 28, 37].

Role of guide rna (grna)

The gRNA is a synthetic construct composed of two essential regions which are Spacer region – A 20-nucleotide sequence complementary to the target DNA [27, 33] and Scaffold region – Binds to the Cas protein and forms a complex for DNA targeting [1, 23].

Once introduced into the cell, the gRNA forms a ribonucleoprotein (RNP) complex with the Cas protein. This complex is guided to the DNA sequence of interest through base pairing between the spacer and the target DNA [10, 11, 16].

Recognition of the pam sequence

A critical feature ensuring specificity is the requirement for a short DNA motif adjacent to the target—known as the Protospacer Adjacent Motif (PAM) [27, 33, 36]. For the widely used Streptococcus pyogenes Cas9 (SpCas9), the PAM is 5´-NGG-3´, where ‘N’ can be any nucleotide [1, 28]. Without a valid PAM, the CRISPR-Cas9 complex will not bind or cleave, thereby minimizing unintended off-target effects [7, 20, 36].

 

 

Dna cleavage by cas nuclease

Upon successful recognition, the Cas9 protein induces a double-stranded break (DSB) at the targeted site via its two nuclease domains that are HNH domain – Cleaves the DNA strand complementary to the gRNA [24, 29], RuvC domain – Cleaves the non-complementary strand [33, 36].

This cleavage results in a blunt-end DSB, which activates endogenous DNA repair processes [4, 25, 26].

Dna repair pathways

Two primary DNA repair mechanisms are employed by the cell post-cleavage where first is Non-Homologous End Joining (NHEJ): Fast and error-prone; often leads to insertions or deletions (indels), causing frameshifts or gene knockouts[5, 29] and second is Homology-Directed Repair (HDR): Requires a  mologous DNA template; enables precise gene correction, knock-in, or sequence replacement[26, 32]. While NHEJ dominates in most mammalian cells, HDR can be enhanced by co-delivering donor DNA templates during gene editing [10, 18].

Transcriptional regulation using dcas9

Beyond DNA cleavage, CRISPR systems have been engineered for gene regulation by utilizing catalytically inactive Cas9 (dCas9), a version of Cas9 that binds DNA without cutting it [23, 24, 28]. Where it involves two phases i.e., CRISPR-i (Interference): dCas9 fused to repressor domains (e.g., KRAB) silences gene expression [30, 33] and CRISPR-a (Activation): dCas9 fused to activators (e.g., VP64) enhances transcription [29, 34]. This approach enables reversible and non-permanent regulation of gene expression, useful for functional genomics and disease modeling [26, 35, 37].

Epigenetic and rna-level modulation

Emerging CRISPR variants extend beyond genome editing by Epigenetic Editing: dCas9 fused with enzymes such as DNA methyltransferases or histone modifiers can regulate gene expression epigenetically and RNA Editing: Cas13 targets and cleaves single-stranded RNA, making it suitable for correcting RNA-level errors in real time, especially in viral infections and transcriptome studies [28, 37, 38].

Summary

The CRISPR-Cas system functions as a versatile platform for genomic and transcriptomic engineering [5, 6].  Its ability to introduce site-specific changes, regulate gene expression, and modulate epigenetic marks underscores its utility in both therapeutic and research settings [17, 24, 33]. A detailed understanding of its mechanism is essential for designing effective strategies in targeted drug delivery and gene therapy [8, 12, 22].

CRISPR-CAS SYSTEMS IN TARGETED DRUG DELIVERY

Introduction to delivery challenges

One of the major barriers in translating CRISPR-Cas technology into clinical success is the efficient and safe delivery of its core components—Cas protein, guide RNA (gRNA), and donor DNA—into the target cells or tissues [6, 9, 13]. Naked CRISPR components are highly unstable, prone to enzymatic degradation, and often unable to cross cellular membranes. Moreover, uncontrolled systemic delivery can cause off-target genome editing, immunogenicity, and toxicity [14, 17, 23]. Therefore, precise and localized delivery of CRISPR-Cas machinery is essential to ensure therapeutic safety and efficacy [8, 16]. To address these limitations, several delivery platforms, including viral vectors and non-viral nanocarriers, are being actively developed [12, 18, 22].

Delivery forms of crispr components

CRISPR tools can be delivered in multiple formats, each requiring a specific delivery strategy here first format is plasmid DNA: encodes cas9 and gRNA but carries the risk of prolonged expression and off-target editing[27, 31], second is mRNA: encodes Cas protein and is translated intracellularly; offers transient expression and improved safety[10, 18] and the third is ribonucleoprotein (RNP) complex: pre-assembled cas9 protein with gRNA, providing high editing efficiency and rapid action with reduced off-target effects[11, 16, 21].

Each format must be optimized to ensure intracellular delivery and efficient genome accessibility [6, 12, 32].

Figure 1. Illustration shows the guide RNA (gRNA) directs Cas9 endonuclease to a specific DNA sequence, where Cas9 cleaves the DNA to create a double-strand break. The cell then repairs the break either via Non-Homologous End Joining (NHEJ) which often introduces indels, or via Homology Directed Repair (HDR) using supplied donor DNA.

Viral delivery systems

Viral vectors are among the most efficient carriers of genetic material and have been widely used in gene therapy [15, 28]. Common viral systems include Adeno-associated virus (AAV): Exhibits strong tissue tropism and low immunogenicity, but its cargo capacity is limited to ~4.7 kb [10, 24], Lentivirus: Integrates into the host genome, supporting long-term expression¹³˒²⁹ and Adenovirus: Provides high transduction efficiency but has greater immunogenicity [22, 35].

Despite their efficiency, viral vectors pose risks such as insertional mutagenesis, immune responses, and limited packaging capacity, which have accelerated the shift toward non-viral platforms [6, 14, 17].

Non-viral nanoparticle delivery systems

Nanotechnology-based delivery systems are gaining prominence due to their customizable design, lower immunogenicity, and potential for co-delivery of multiple biomolecules[8, 12, 17] key nanocarriers include Lipid Nanoparticles (LNPs): Extensively used in mRNA vaccines and efficient for delivering mRNA and RNPs [18, 20], Polymeric Nanoparticles: Biodegradable and tunable carriers, such as PLGA, PEI, and chitosan [22, 31], Gold Nanoparticles: Easily functionalized and trackable, useful for gene editing applications [13, 16], Dendrimers: Branched polymers offering high payload capacity with low toxicity [19, 35], Exosomes: Naturally derived vesicles capable of targeted delivery with minimal immune activation [10, 11, 18].

Recent advancements in nanocarrier systems have demonstrated the therapeutic potential of solid lipid nanoparticles and liposomal formulations in enhancing drug bioavailability and targeted delivery. For instance, solid lipid nanoparticles have been successfully developed for improved therapeutic performance of bioactive compounds [46], while liposome-based delivery systems have shown enhanced encapsulation efficiency and controlled release characteristics [47]. These formulation strategies provide a conceptual and technological framework that can be adapted for CRISPR-Cas component delivery, particularly for improving stability, cellular uptake, and tissue-specific targeting in gene therapy applications.These nanocarriers enhance intracellular trafficking by facilitating endosomal escape, nuclear entry, and protection of CRISPR components from degradation.

Cell and tissue-specific targeting

Targeted delivery strategies aim to restrict CRISPR activity to diseased cells, minimizing off-target effects on healthy tissues [6, 9, 13]. Key approaches are Surface modification with ligands: Nanoparticles can be conjugated with antibodies, peptides, or aptamers for receptor-mediated targeting [17, 22], Stimuli-responsive systems: Engineered to respond to pH, redox, or temperature changes within the tumor microenvironment [20, 32] and Tissue-specific promoters: Incorporated into plasmid-based systems to ensure expression only in the desired cell type [28, 30].

For instance, nanoparticles conjugated with folic acid selectively target cancer cells overexpressing folate receptors [12, 18].

Recent innovations in delivery platforms

Emerging delivery approaches have shown great potential in overcoming current challenges and new innovations emerged are Microneedles: Enable localized, minimally invasive delivery of CRISPR payloads through the skin [21, 38], Hydrogels: Provide controlled release for tissue engineering and regenerative medicine[32, 39], Biodegradable implants: Offer long-acting delivery for chronic therapeutic conditions[19, 29], Cell-penetrating peptides (CPPs): Short amino acid sequences that facilitate intracellular transport of CRISPR components[40].

These innovations promise to improve the therapeutic index, safety, and patient compliance of CRISPR-based therapies.

Summary

In summary, delivery remains one of the most critical challenges for CRISPR-Cas systems [5, 9, 20]. An ideal delivery system should combine high transfection efficiency, low immunogenicity, tissue specificity, and sustained intracellular availability [8, 17, 22]. With continuous advancements in nanomedicine and bioengineering, CRISPR-based targeted therapies are steadily progressing toward clinical translation [12, 16, 32, 34].

APPLICATIONS OF CRISPR-CAS IN TARGETED DRUG DELIVERY

Precision gene editing for disease-specific therapies

The major strength of CRISPR-Cas systems lies in their ability to introduce precise genetic modifications at targeted loci [1, 2, 6]. This feature is currently being explored for the development of therapies against a wide range of inherited and acquired disorders [3, 4]. Examples include : Cancer: CRISPR has been used to knock out immune checkpoint genes (e.g., PD-1) in T cells to enhance their anti-tumor activity [15, 19, 28], Sickle Cell Disease and β-Thalassemia: Editing the BCL11A gene with CRISPR-Cas9 reactivates fetal hemoglobin production, demonstrating curative potential[16, 25] and Cystic Fibrosis: CRISPR is being investigated to repair mutations in the CFTR gene responsible for the disease pathology [18, 30].

CRISPR-based drug target discovery

Genome-wide CRISPR screening has revolutionized drug target identification by enabling both loss-of-function (LoF) and gain-of-function (GoF) studies [5, 6, 33]. These platforms have been instrumental in identifying novel therapeutic pathways in Antibiotic resistance, Chemotherapy resistance, Pathogen virulence. Such approaches significantly accelerate the drug discovery pipeline and improve precision targeting in modern pharmacology [22, 32].

Delivery of CRISPR components using nanocarriers

Efficient delivery systems are critical for the therapeutic application of CRISPR tools. Multiple nanocarriers have been engineered to transport CRISPR components such as gRNA and Cas proteins with high specificity[6, 8] and such carriers are Lipid Nanoparticles (LNPs): Widely employed for mRNA-based CRISPR constructs, particularly in liver-targeted therapies[10, 18, 28], Polymeric Nanoparticles: Biodegradable carriers like PLGA are commonly used to deliver Cas9-gRNA complexes[12, 22, 31], Exosomes: Endogenous vesicles capable of crossing the blood-brain barrier and delivering CRISPR cargo[17, 35] and Gold Nanoparticles (AuNPs): Provide biocompatibility and surface tunability for tissue-specific delivery[13, 16, 39].

These nanocarriers ensure enhanced specificity, reduced immunogenicity, and improved therapeutic efficacy [32, 34, 39].

CRISPR in infectious disease management

Beyond human gene editing, CRISPR has been adapted to directly target and degrade viral genomes, offering novel therapeutic strategies against infectious diseases [27, 28]. Examples include: HIV: CRISPR has been used to excise integrated HIV proviral DNA from host cells [30, 38] and Hepatitis B Virus (HBV): CRISPR-mediated degradation of covalently closed circular DNA (cccDNA) holds promise for functional cures [29, 33]. These strategies represent a transformative approach toward achieving cures for chronic viral infections [26, 36].

CRISPR in Neurodegenerative Disorders

Neurodegenerative disorders represent a significant global health burden due to progressive neuronal dysfunction and limited regenerative capacity of the central nervous system. Among these, Alzheimer’s disease is the leading cause of dementia worldwide. Alzheimer’s disease is characterized by extracellular amyloid-beta (Aβ) plaque deposition, intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein, oxidative stress, mitochondrial dysfunction, and chronic neuroinflammation, all contributing to synaptic loss and cognitive decline [41].

Mutations in APP, PSEN1, and PSEN2 genes are associated with familial forms of Alzheimer’s disease. CRISPR-Cas9 technology offers the possibility of selectively editing these pathogenic mutations to reduce amyloid-beta production at its source. Preclinical studies have demonstrated that targeted gene editing in neuronal models can modulate amyloidogenic pathways and attenuate disease pathology [42,43]. Additionally, CRISPR interference (CRISPRi) approaches may regulate tau expression without inducing double-stranded DNA breaks, potentially improving therapeutic safety [24].

Similarly, Parkinson’s disease is characterized by progressive degeneration of dopaminergic neurons in the substantia nigra and aggregation of misfolded alpha-synuclein protein. Genetic mutations in SNCA, LRRK2, PINK1, and PARK7 genes have been implicated in disease pathogenesis. CRISPR-based genome editing provides opportunities to correct pathogenic mutations or suppress abnormal alpha-synuclein expression, thereby addressing the molecular drivers of neurodegeneration [28,44].

A major challenge in applying CRISPR for neurodegenerative diseases is efficient delivery across the blood–brain barrier (BBB). Emerging strategies involving lipid nanoparticles, engineered exosomes, and adeno-associated viral vectors are being investigated to enable targeted central nervous system gene editing [17,34]. Although clinical translation remains in early stages, CRISPR-based approaches represent a promising shift from symptomatic management toward disease-modifying therapies in neurodegenerative ddisorders.

CISPR in Parkinson Disease

Similarly, Parkinson’s disease is characterized by progressive degeneration of dopaminergic neurons in the substantia nigra and aggregation of misfolded alpha-synuclein protein. The disease pathology involves oxidative stress, mitochondrial dysfunction, neuroinflammation, and impaired dopamine synthesis, as discussed in recent literature [45]. Genetic mutations in SNCA, LRRK2, PINK1, and PARK7 genes have been implicated in disease pathogenesis. CRISPR-based genome editing provides opportunities to correct pathogenic mutations or suppress abnormal alpha-synuclein expression, thereby addressing the molecular drivers of neurodegeneration [28 ,44].

Tissue-specific delivery and regulation

Recent advances have focused on achieving spatial and temporal control of CRISPR activity through Tissue-specific promoters, Light-activated CRISPR systems, Drug-inducible Cas expression systems. These innovations reduce off-target editing and enable precise site-specific gene regulation, thereby enhancing the safety profile of CRISPR therapies.

CRISPR-CAS SYSTEMS IN GENE THERAPY

Introduction to gene therapy and crispr

Gene therapy involves the introduction, removal, or alteration of genetic material within a patient’s cells to treat or prevent disease [29, 30]. The advent of CRISPR-Cas systems has dramatically expanded the potential of gene therapy, offering a more efficient, accurate, and programmable tool for genome engineering [1, 2, 6]. Unlike traditional methods (e.g., viral vector-based gene insertion), CRISPR enables precise and targeted modifications at endogenous loci, thereby minimizing insertional mutagenesis and off-target effects [13, 33].

Key Advantages are Specificity, Efficiency and Versatility

CRISPR approaches in gene therapy

ex vivo gene editing

In this approach, patient cells are extracted, genetically modified outside the body using CRISPR, and then reintroduced [15, 19, 28]. This strategy is widely applied in CAR-T Cell Therapy: Engineering T cells to express chimeric antigen receptors for cancer immunotherapy [29, 38], Sickle Cell Disease: Ex vivo editing of hematopoietic stem cells to disrupt BCL11A and restore fetal hemoglobin expression [16, 25] and Immunodeficiencies: Correction of mutations in genes such as IL2RG in Severe Combined Immunodeficiency (SCID) [30, 39].

in vivo gene editing

Here, CRISPR-Cas components are directly delivered into the patient’s body to correct genes in specific tissues such as  Liver Disorders: Lipid nanoparticles are employed to correct genetic mutations in hepatocytes[18, 20], Eye Diseases: Subretinal delivery of CRISPR-Cas9 has shown promise in conditions such as Leber congenital amaurosis[29, 31] and Muscular Dystrophy: Systemic delivery enables gene correction for Duchenne muscular dystrophy in muscle tissues[19, 26].

CRISPR modalities for therapeutic applications

CRISPR-based gene therapy is no longer confined to DSB-induced repair. Several advanced modalities have emerged such as CRISPRa/CRISPRi: Utilize catalytically inactive Cas9 (dCas9) fused with transcriptional activators or repressors to modulate gene expression without inducing DNA cleavage[23, 24, 34] ,  Base Editing: Enables single nucleotide conversions (e.g., C→T or A→G) without generating DSBs, making it ideal for correcting point mutations[26, 36] and Prime Editing: A next-generation approach that combines Cas9 nickase with reverse transcriptase to perform precise edits including insertions, deletions, and base substitutions[32, 37]. These innovations enable the treatment of genetic diseases with minimal genomic disruption, thereby increasing the safety of clinical applications.

Delivery strategies for CRISPR-based gene therapy

Efficient delivery of CRISPR tools into target tissues remains one of the major bottlenecks[6, 9]. The following platforms are widely explored:

viral vectors:

·      Adeno-associated virus (AAV): High transduction efficiency but limited cargo capacity [34].

·      Lentivirus: Capable of integrating into the host genome but raises concerns of insertional oncogenesis [35].

non-viral vectors:

·      Lipid nanoparticles (LNPs): Currently employed in CRISPR-based clinical trials for liver diseases [20].

·      Electroporation: Widely used in ex vivo applications such as T-cell modification [12].

·      Gold nanoparticles and polymers: Under investigation for targeted tissue delivery [22].

These approaches are being extended to complex diseases such as Alzheimer’s, cancer, and metabolic disorders [15, 29]. With continuous advancements, the dream of personalized and curative genetic medicine is becoming increasingly attainable.

Clinical trials and milestones

Several clinical trials are currently underway, confirming the clinical translation potential of CRISPR-based gene therapies [15, 17]. Notable examples include: CTX001 (CRISPR Therapeutics + Vertex): An ex vivo therapy developed for sickle cell disease and β-thalassemia [16, 25], EDIT-101 (Editas Medicine): The first in vivo CRISPR therapy targeting LCA10 in retinal tissue [29, 1] and NTLA-2001 (Intellia Therapeutics): An in vivo therapy for transthyretin amyloidosis using LNP-delivered CRISPR [18, 20, 32]. These trials mark a paradigm shift in medicine, demonstrating the feasibility of editing human genes to treat previously untreatable conditions.

Challenges in crispr gene therapy

Despite remarkable progress, several hurdles remain like Off-target effects: Unintended DNA modifications may lead to oncogenesis or toxicity [20, 26], Immune response: Pre-existing immunity to Cas proteins can reduce efficacy or trigger adverse reactions [13, 22], Ethical issues: Germline editing, consent, and equitable access remain subjects of global debate [23, 28, 30] and Regulatory approvals: Long-term safety and efficacy data are required before worldwide regulatory endorsement [24, 34].

Future prospects

The field of CRISPR-based gene therapy is evolving rapidly. Future directions include Development of novel Cas variants with improved specificity [26, 36], Integration of synthetic biology for programmable and responsive gene circuits [32, 37], Application of AI-guided gRNA design to enhance safety and efficiency [17, 22], Extension of applications to complex diseases such as Alzheimer’s, cancer, and metabolic syndromes [15, 29]. The dream of personalized, curative genetic medicine is becoming increasingly attainable with these advancements.

CHALLENGES AND LIMITATIONS OF CRISPR-CAS SYSTEMS

Despite its revolutionary impact on biomedical sciences, the application of CRISPR-Cas systems in targeted drug delivery and gene therapy is not devoid of challenges [6, 7]. These obstacles span technical, biological, regulatory, and ethical domains, which must be thoroughly addressed before CRISPR-based therapeutics can be adopted for widespread clinical use [20, 21, 23].

Off-target effects and genetic instability

One of the most significant limitations is the potential for off-target effects, where the Cas nuclease cleaves DNA at unintended loci [36, 37]. This may result in: Mutagenesis: Random insertions or deletions (indels) at off-target sites[29, 30], Chromosomal rearrangements: Large deletions, inversions, or translocations compromising genomic integrity[33, 34], Tumorigenesis risk: Mutations in proto-oncogenes or tumor suppressor genes due to off-target cleavage [35, 38] and Mitigation strategies: Development of high-fidelity Cas variants (e.g., SpCas9 HF1, eSpCas9), improved gRNA design algorithms, and transient delivery methods reduce off-target risks [36, 39, 40].

Delivery barriers in vivo

Effective delivery of CRISPR components remains a critical challenge, especially for systemic or organ-specific applications. Major hurdles include: Endosomal entrapment: Failure of CRISPR payload to escape endosomes after cellular uptake [17, 18], Degradation by nucleases: Unprotected gRNA or mRNA may degrade before reaching target cells [11, 13] and Inefficient tissue penetration: Particularly in solid tumors or central nervous system (CNS) diseases [22,32].

Advanced nanocarriers, such as lipid nanoparticles, cell-penetrating peptides, and virus-like particles, are being designed to overcome these obstacles [16, 19, 31].

Immune responses to cas proteins

Since Cas enzymes (e.g., Cas9) are derived from bacteria like Streptococcus pyogenes, they are recognized as foreign by the human immune system [20, 21]. This can result in: Adaptive immune responses: Activation of cytotoxic T cells and production of neutralizing antibodies [22, 29], Inflammation: Local or systemic inflammation compromising therapeutic outcomes [23, 34] and Reduced efficacy upon repeated dosing: Immunological memory diminishes the success of subsequent treatments [30, 35]. Potential solutions include engineering humanized Cas proteins, using immune-suppressive regimens, or selecting immune-privileged delivery sites [25, 26, 29].

Ethical and regulatory concerns

The power to edit human genomes raises several ethical and societal concerns, particularly regarding: Germline editing: Heritable modifications raise questions of consent, designer babies, and genetic inequality [30, 33]. Equity in access: High costs may limit CRISPR therapy accessibility in underdeveloped regions [26, 27] and Bioterrorism potential: CRISPR’s ease of use could theoretically be misused for harmful purposes [24, 34]. International regulatory agencies are still developing frameworks to manage these emerging challenges responsibly [21, 35, 38].

Genetic mosaicism and incomplete editing

In vivo CRISPR applications may result in genetic mosaicism, where only a subset of cells is edited. This can cause: Reduced therapeutic efficacy: Incomplete correction of disease-causing mutations [29, 31] And data interpretation: Variable editing efficiency across tissues complicates therapeutic monitoring [17, 32].

Technologies like base editing and prime editing aim to increase precision and efficiency [26, 36].

Long-term safety and integration risks

Although CRISPR is generally non-integrating, some delivery platforms (e.g., viral vectors) pose risks like Insertional mutagenesis: Random insertion of CRISPR constructs into the host genome [35, 37]. Sustained Cas expression: Prolonged presence of Cas proteins may increase off-target effects [20, 33] and Delayed toxicities: Long-term effects, including immunogenicity and malignancies, remain unknown [21] while Rigorous preclinical models and long-term clinical trials are required to assess these risks thoroughly [24, 34].

Scale-up and manufacturing challenges

Commercial production of CRISPR therapeutics must address: Scalable synthesis: Reproducible production of guide RNAs, Cas enzymes, and nanocarriers [31, 32]. Cost-effectiveness: High costs due to GMP compliance and complex logistics [25, 30] and Batch consistency and purity: Critical for regulatory approval and safety assurance [29, 34]. Standardization of manufacturing practices and automation will be essential in overcoming these limitations.

FUTURE PERSPECTIVES AND EMERGING TRENDS

The advent of CRISPR-Cas systems has catalyzed an unprecedented revolution in genetic engineering and biomedical sciences [1, 2]. As the field transitions from proof-of-concept studies toward widespread clinical translation, several transformative trends are emerging [2]. These include innovations in Cas proteins, refined delivery mechanisms, integration with artificial intelligence, ethical governance, and applications in synthetic biology and global health [3, 4].

Development of next-generation cas systems and editors

While Streptococcus pyogenes Cas9 (SpCas9) remains the most extensively studied CRISPR-associated protein, limitations such as off-target cleavage and delivery constraints have stimulated exploration of alternative Cas variants [1, 4, 12, 14]. Future research is increasingly focused on:

·         Cas12a (Cpf1): Smaller in size, capable of staggered DNA cuts, and independent of tracr-RNA, Cas12a enables multiplexed and compact editing strategies [3, 4].

·         Cas13a/b/d systems: RNA-targeting CRISPR enzymes allowing transient gene expression regulation, utilized in viral diagnostics (e.g., SHERLOCK) and neurodegenerative disease modelling [5].

·         Base Editors: Fusion proteins of catalytically dead Cas9 (dCas9) or Cas9 nickase with deaminases (cytidine or adenine) allow precise single-nucleotide edits without double-stranded breaks (DSBs), minimizing genotoxicity [6].

·         Prime Editing: Enables versatile and precise insertions, deletions, and all 12 types of point mutations using a prime editor guide RNA (pegRNA) and a reverse transcriptase-Cas9 fusion protein [7].

These next-generation editors expand the spectrum of correctable genetic disorders while reducing risks associated with traditional DSB-based methods.

Personalized and precision crispr therapeutics

Tailoring gene-editing strategies to individual genomic and epigenomic contexts is gaining traction as CRISPR moves toward clinical application. In oncology, CRISPR can reprogram autologous T cells to target patient-specific neoantigens through CRISPR-modified CAR-T therapies [9].

Ai-driven crispr design and predictive modeling

Artificial intelligence (AI) and machine learning (ML) increasingly enhance CRISPR research [11]. Computational tools improve precision, safety, and efficiency through sgRNA design optimization: ML platforms like CRISPR-scan, Deep-CRISPR, and Azimuth model on-target activity and off-target risks [11], Off-target prediction algorithms: Tools like Elevation and CRISPOR utilize genome-wide data to predict and mitigate unintended edits [12] and Automated image and data analysis: AI-based microscopy tools accelerate phenotypic screening in high-throughput CRISPR screens[13]. Integration of AI with high-content screening enhances CRISPR’s utility in drug discovery and gene network elucidation [11, 13].

Integration with smart nanocarriers and responsive delivery systems

Efficient, targeted delivery remains a major bottleneck in CRISPR-Cas system translation [6, 14]. Emerging nanotechnologies provide promising solutions via stimuli-responsive and biomimetic carriers which are  Lipid nanoparticles (LNPs): Used in mRNA COVID-19 vaccines and CRISPR in vivo trials (e.g., NTLA-2001 for ATTR amyloidosis)[16], pH-sensitive polymers: Enable endosomal escape and site-specific release in acidic tumor microenvironments[14, 15], Exosome-based delivery: Naturally occurring vesicles with low immunogenicity and intrinsic targeting [4, 15] and Cell-penetrating peptides (CPPs) and aptamer-conjugated systems: Facilitate active, tissue-specific delivery of CRISPR cargos[14, 1, 5].

Future smart delivery platforms are expected to exhibit modularity, multi-payload capacity, and organelle-targeting precision, particularly for mitochondrial and nuclear gene editing [17].

Ethical, legal, and societal implications (elsi)

The rapid evolution of CRISPR technologies has outpaced ethical and legal frameworks [18]. Key areas of concern include:

·         Germline editing: Heritable modifications raise bioethical dilemmas regarding designer babies and eugenics [18].

·         Informed consent in vulnerable populations: Trials in paediatric or cognitively impaired individuals require careful ethical consideration [18].

·         Data privacy and ownership: Genomic data integration into therapy necessitates stringent governance over consent, ownership, and misuse [18].

Global initiatives, including the WHO Expert Advisory Committee on Human Genome Editing, aim to establish ethical guidelines, regulatory oversight, and public engagement models [19].

Crispr in synthetic biology, biosensing, and bio-computing

CRISPR integration with synthetic biology is enabling programmable biological circuits and engineered organisms [20]. Emerging directions include Logic gate construction: CRISPR enables synthetic regulatory networks for biosensing and therapeutic applications [20], In vivo biosensors: CRISPR-powered diagnostics like SHERLOCK and DETECTR allow rapid, sensitive pathogen detection [5, 20] and Cellular memory and data storage: CRISPR arrays encode digital information in living cells via DNA recording [21]. These developments position CRISPR as a tool for therapy, biological computation, surveillance, and synthetic system design [20, 21].

 

 

Expansion to global health and low-resource applications

Efforts are ongoing to democratize CRISPR technologies for low-resource settings, promoting equitable global impact [22]. Major developments include Low-cost, portable diagnostics: Paper-based CRISPR test kits for diseases like Zika, dengue, and TB [22], Thermostable formulations: Enable storage and transport without cold-chain logistics [23] and Oral or transdermal delivery systems: Non-invasive methods suitable for populations with limited healthcare access [24]. These innovations aim to bridge the gap between cutting-edge research and real-world applications in underdeveloped or rural regions [22, 23].

 

CONCLUSION

The journey of the CRISPR-Cas system from a microbial immune defense to a sophisticated and programmable genome-editing tool reflects a transformative advancement in biomedical science [12]. Over the last decade, this technology has evolved into a powerful, precise, and adaptable instrument that is reshaping the future of gene therapy and targeted drug delivery with unprecedented promise [12]. The versatility of CRISPR-Cas, particularly its ability to accurately recognize and edit specific DNA sequences, has catalyzed a paradigm shift in the prevention, understanding, and potential cure of a wide range of genetic and non-genetic diseases [34].

Rewriting the future of disease treatment

At the heart of CRISPR-Cas's therapeutic utility lies its unparalleled potential to directly target the genetic root causes of disease [12]. By enabling researchers to knock out, correct, or insert genes with remarkable specificity, the system allows for a fundamental rewriting of cellular behavior [3]. This approach offers significant advantages over traditional treatments, which often manage only symptoms without addressing underlying genetic aberrations [4]. Diseases once considered incurable, such as monogenic disorders, cancers, and chronic infections, are now being revisited with renewed optimism through CRISPR-based therapies [56].

 

Integration with targeted drug delivery platforms

The efficacy of CRISPR-mediated therapy is further enhanced when combined with intelligent and biocompatible drug delivery systems [6, 14]. Lipid-based nanoparticles, viral vectors (AAV, lentivirus), and polymer-based nanocarriers have shown immense potential in delivering CRISPR components (e.g., Cas9 mRNA, sgRNA, or ribonucleoproteins) specifically to affected cells or tissues while minimizing degradation, immune detection, and off-target accumulation [14, 15]. Novel delivery platforms such as extracellular vesicles, exosomes, microneedles, and hydrogels are also under investigation to improve pharmacokinetics and biodistribution of CRISPR payload [15, 17]. The combination of programmable gene editing with advanced delivery vehicles paves the way for next-generation personalized therapeutics [17].

Therapeutic breakthroughs and clinical evidence

Emerging clinical evidence validates the preclinical promise of CRISPR-Cas technologies [18]. Early-phase clinical trials in sickle cell disease, β-thalassemia, transthyretin amyloidosis, and hereditary blindness have demonstrated substantial therapeutic benefits and manageable safety profiles [18, 19]. CRISPR-engineered T cells are also being explored as a novel approach in immuno-oncology for refractory cancers by enhancing immune recognition of tumor cells [9]. These results have spurred regulatory discussions and attracted significant investment from public and private sectors, accelerating the pace of clinical translation [18, 19].

Addressing the challenges ahead

Despite its promise, several critical challenges remain such as Off-target mutations: Unintended edits continue to pose safety concerns, especially for in vivo therapies[7], Immunogenicity: Host immune responses against bacterial-derived Cas proteins may compromise efficacy or cause inflammation[10], Delivery limitations: Efficient, tissue-specific, and repeatable delivery of CRISPR components remains a bottleneck for clinical adoption[6, 14] and Ethical dilemmas: Germline editing, consent in pediatric applications, and long-term genomic monitoring continue to raise profound ethical and societal questions[18].

Ongoing research focuses on high-fidelity Cas variants (Cas12, Cas13, Cas10), non-viral delivery systems, epigenetic editing tools, and AI-assisted sgRNA design to enhance precision and safety[7,11,12].

Looking forward: the crispr frontier

CRISPR-Cas systems represent more than molecular scissors—they provide a universal toolkit for future medicine [12]. Integrating genome editing with diagnostics, regenerative medicine, immunotherapy, and synthetic biology opens limitless opportunities [5, 20]. From targeted therapies for neurodegenerative disorders to engineering disease-resistant crops, CRISPR’s long-term implications extend far beyond human therapeutics [20, 21]. Sustained interdisciplinary collaboration across nanomedicine, molecular biology, pharmacology, regulatory sciences, and bioethics, along with global governance and policy-making, will be essential to ensure equitable, safe, and ethical access to CRISPR-based interventions [18, 19].

Final reflection

In conclusion, the fusion of CRISPR-Cas systems with targeted drug delivery and gene therapy strategies has created a robust framework to treat diseases at their molecular core [6, 14]. While challenges remain, the promise of precision, personalization, and permanence in therapeutic interventions is rapidly becoming a clinical reality [7, 18]. The coming years are likely to witness CRISPR's transition from a groundbreaking laboratory tool to a mainstream pillar of medical care, ushering in a new era of genetic medicine that is safer, smarter, and more human-centered [18, 19].

CONFLICT OF INTEREST

There is not any Conflict of Interest.

ACKNOWLEDGEMENT

Authors would like to express their sincere thanks to the Management of Sanskar Educational Group for utilizing their resources.

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