A designed recombinant fusion protein for targeted delivery of siRNA to the mouse brain

Bio-Nano Toolbox for Precision Alzheimer's Disease Gene Therapy

Alzheimer's disease (AD) is the most burdensome aging-associated neurodegenerative disorder, and its treatment encounters numerous failures during drug development. Although there are newly approved in-market β-amyloid targeting antibody solutions, pathological heterogeneity among patient populations still challenges the treatment outcome. Emerging advances in gene therapies offer opportunities for more precise personalized medicine; while, major obstacles including the pathological heterogeneity among patient populations, the puzzled mechanism for druggable target development, and the precision delivery of functional therapeutic elements across the blood-brain barrier remain and limit the use of gene therapy for central neuronal diseases. Aiming for "precision delivery" challenges, nanomedicine provides versatile platforms that may overcome the targeted delivery challenges for AD gene therapy. In this perspective, to picture a toolbox for AD gene therapy strategy development, the most recent advances from benchtop to clinics are highlighted, possibly available gene therapy targets, tools, and delivery platforms are outlined, their challenges as well as rational design elements are addressed, and perspectives in this promising research field are discussed.

Protein-based delivery systems for RNA delivery

RNA-based therapeutics have emerged as promising approaches to modulate gene expression and generate therapeutic proteins or antigens capable of inducing immune responses to treat a variety of diseases, such as infectious diseases, cancers, immunologic disorders, and genetic disorders. However, the efficient delivery of RNA molecules into cells poses significant challenges due to their large molecular weight, negative charge, and susceptibility to degradation by RNase enzymes. To overcome these obstacles, viral and non-viral vectors have been developed, including lipid nanoparticles, viral vectors, proteins, dendritic macromolecules, among others. Among these carriers, protein-based delivery systems have garnered considerable attention due to their potential to address specific issues associated with nanoparticle-based systems, such as liver accumulation and immunogenicity. This review provides an overview of currently marketed RNA drugs, underscores the significance of RNA delivery vector development, delineates the essential characteristics of an ideal RNA delivery vector, and introduces existing protein carriers for RNA delivery. By offering valuable insights, this review aims to serve as a reference for the future development of protein-based delivery vectors for RNA therapeutics.

Cell primitive-based biomimetic nanomaterials for Alzheimer's disease targeting and therapy

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, which is not just confined to the older population. Although developments have been made in AD treatment, various limitations remain to be addressed. These are partly contributed by biological hurdles, such as the blood-brain barrier and peripheral side effects, as well as by lack of carriers that can efficiently deliver the therapeutics to the brain while preserving their therapeutic efficacy. The increasing AD prevalence and the unavailability of effective treatments have encouraged researchers to develop improved, convenient, and affordable therapies. Functional materials based on primitive cells and nanotechnology are emerging as attractive therapeutics in AD treatment. Cell primitives possess distinct biological functions, including long-term circulation, lesion site targeting, and immune suppression. This review summarizes the challenges in the delivery of AD drugs and recent advances in cell primitive-based materials for AD treatment. Various cell primitives, such as cells, extracellular vesicles, and cell membranes, are presented together with their distinctive biological functions and construction strategies. Moreover, future research directions are discussed on the basis of foreseeable challenges and perspectives.

siRNA drug delivery across the blood-brain barrier in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease with a few FDA-approved drugs that provide modest symptomatic benefits and only two FDA-approved disease-modifying treatments for AD. The advancements in understanding the causative genes and non-coding sequences at the molecular level of the pathophysiology of AD have resulted in several exciting research papers that employed small interfering RNA (siRNA)-based therapy. Although siRNA is being sought by academia and biopharma industries, several challenges still need to be addressed. We comprehensively report the latest advances in AD pathophysiology, druggable targets, ongoing clinical trials, and the siRNA-based approaches across the blood-brain barrier for addressing AD. This review describes the latest delivery systems employed to address this barrier. Critical insights and future perspectives on siRNA therapy for AD are also provided.

Acan downregulation in parvalbumin GABAergic cells reduces spontaneous recovery of fear memories

While persistence of fear memories is essential for survival, a failure to inhibit fear in response to harmless stimuli is a feature of anxiety disorders. Extinction training only temporarily suppresses fear memory recovery in adults, but it is highly effective in juvenile rodents. Maturation of GABAergic circuits, in particular of parvalbumin-positive (PV+) cells, restricts plasticity in the adult brain, thus reducing PV+ cell maturation could promote the suppression of fear memories following extinction training in adults. Epigenetic modifications such as histone acetylation control gene accessibility for transcription and help couple synaptic activity to changes in gene expression. Histone deacetylase 2 (Hdac2), in particular, restrains both structural and functional synaptic plasticity. However, whether and how Hdac2 controls the maturation of postnatal PV+ cells is not well understood. Here, we show that PV+- cell specific Hdac2 deletion limits spontaneous fear memory recovery in adult mice, while enhancing PV+ cell bouton remodeling and reducing perineuronal net aggregation around PV+ cells in prefrontal cortex and basolateral amygdala. Prefrontal cortex PV+ cells lacking Hdac2, show reduced expression of Acan, a critical perineuronal net component, which is rescued by Hdac2 re-expression. Pharmacological inhibition of Hdac2 before extinction training is sufficient to reduce both spontaneous fear memory recovery and Acan expression in wild-type adult mice, while these effects are occluded in PV+-cell specific Hdac2 conditional knockout mice. Finally, a brief knock-down of Acan expression mediated by intravenous siRNA delivery before extinction training but after fear memory acquisition is sufficient to reduce spontaneous fear recovery in wild-type mice. Altogether, these data suggest that controlled manipulation of PV+ cells by targeting Hdac2 activity, or the expression of its downstream effector Acan, promotes the long-term efficacy of extinction training in adults.

Biodistribution and delivery of oligonucleotide therapeutics to the central nervous system: Advances, challenges, and future perspectives

Considerable advances have been made in the research and development of oligonucleotide therapeutics (OTs) for treating central nervous system (CNS) diseases, such as psychiatric and neurodegenerative disorders, because of their promising mode of action. However, due to the tight barrier function and complex physiological structure of the CNS, the efficient delivery of OTs to target the brain has been a major challenge, and intensive efforts have been made to overcome this limitation. In this review, we summarize the representative methodologies and current knowledge of biodistribution, along with the pharmacokinetic/pharmacodynamic (PK/PD) relationship of OTs in the CNS, which are critical elements for the successful development of OTs for CNS diseases. First, quantitative bioanalysis methods and imaging-based approaches for the evaluation of OT biodistribution are summarized. Next, information available on the biodistribution profile, distribution pathways, quantitative PK/PD modeling, and simulation of OTs following intrathecal or intracerebroventricular administration are reviewed. Finally, the latest knowledge on the drug delivery systems to the brain via intranasal or systemic administration as noninvasive routes for improved patient quality of life is reviewed. The aim of this review is to enrich research on the successful development of OTs by clarifying OT distribution profiles and pathways to the target brain regions or cells, and by identifying points that need further investigation for a mechanistic approach to generate efficient OTs.

Targeting Fibronectin to Overcome Remyelination Failure in Multiple Sclerosis: The Need for Brain- and Lesion-Targeted Drug Delivery

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease with unknown etiology that can be characterized by the presence of demyelinated lesions. Prevailing treatment protocols in MS rely on the modulation of the inflammatory process but do not impact disease progression. Remyelination is an essential factor for both axonal survival and functional neurological recovery but is often insufficient. The extracellular matrix protein fibronectin contributes to the inhibitory environment created in MS lesions and likely plays a causative role in remyelination failure. The presence of the blood–brain barrier (BBB) hinders the delivery of remyelination therapeutics to lesions. Therefore, therapeutic interventions to normalize the pathogenic MS lesion environment need to be able to cross the BBB. In this review, we outline the multifaceted roles of fibronectin in MS pathogenesis and discuss promising therapeutic targets and agents to overcome fibronectin-mediated inhibition of remyelination. In addition, to pave the way for clinical use, we reflect on opportunities to deliver MS therapeutics to lesions through the utilization of nanomedicine and discuss strategies to deliver fibronectin-directed therapeutics across the BBB. The use of well-designed nanocarriers with appropriate surface functionalization to cross the BBB and target the lesion sites is recommended.

Advances in nanoparticle mediated targeting of RNA binding protein for cancer

RNA binding proteins (RBPs) enact a very crucial part in the RNA directive processes. Atypical expression of these RBPs affects many steps of RNA metabolism, majorly altering its expression. Altered expression and dysfunction of RNA binding proteins lead to cancer progression and other diseases. We enumerate various available interventions, and recent findings focused on targeting RBPs for cancer therapy and diagnosis. The treatment, sensitization, chemoprevention, gene-mediated, and virus mediated interventions were studied to treat and diagnose cancer. The application of passively and actively targeted lipidic nanoparticles, polymeric nanoparticles, virus-based particles, and vaccine-based immunotherapy for the delivery of therapeutic agent/s against cancer are discussed. We also discuss the formulation aspect of nanoparticles for achieving delivery at the site of action and ongoing clinical trials targeting RBPs.

Highly Efficient Method for Intracellular Delivery of Proteins Mediated by Cholera Toxin-Induced Protein Internalization

Delivery of functional proteins into cells may help us understand how specific protein influences cell behavior as well as treat diseases caused by protein deficiency or loss-of-function mutations. However, protein cannot enter cells by diffusion. In this work, a novel cell biology tool for delivering recombinant proteins into mammalian cells was developed. We hijacked the intracellular transport routes used by the cholera toxin and took advantage of recent development on split intein that is compatible with denatured conditions and shows an exceptional splicing activity to deliver a protein of interest into mammalian cells. Here, we used green fluorescent protein and apoptin as proofs-of-concept. The results demonstrate that the cholera toxin B subunit alone could deliver other recombinant proteins into cells through either covalent conjugation or noncovalent interaction. Our method offers more than 10-fold better delivery efficiency than the tat cell-penetrating peptide and is selective for ganglioside-rich cells. This study adds a useful tool to the receptor-mediated intracellular targeting toolkit and opens possibility for the selective delivery of therapeutic proteins into ganglioside-rich cells.

Nanotechnology-Assisted RNA Delivery: From Nucleic Acid Therapeutics to COVID-19 Vaccines

In recent years, the main quest of science has been the pioneering of the groundbreaking biomedical strategies needed for achieving a personalized medicine. Ribonucleic acids (RNAs) are outstanding bioactive macromolecules identified as pivotal actors in regulating a wide range of biochemical pathways. The ability to intimately control the cell fate and tissue activities makes RNA-based drugs the most fascinating family of bioactive agents. However, achieving a widespread application of RNA therapeutics in humans is still a challenging feat, due to both the instability of naked RNA and the presence of biological barriers aimed at hindering the entrance of RNA into cells. Recently, material scientists' enormous efforts have led to the development of various classes of nanostructured carriers customized to overcome these limitations. This work systematically reviews the current advances in developing the next generation of drugs based on nanotechnology-assisted RNA delivery. The features of the most used RNA molecules are presented, together with the development strategies and properties of nanostructured vehicles. Also provided is an in-depth overview of various therapeutic applications of the presented systems, including coronavirus disease vaccines and the newest trends in the field. Lastly, emerging challenges and future perspectives for nanotechnology-mediated RNA therapies are discussed.

Development of curcumin-loaded zein nanoparticles for transport across the blood-brain barrier and inhibition of glioblastoma cell growth

Glioblastoma (GBM) is a devastating primary brain tumor resistant to conventional therapies. A major obstacle to GBM treatment is the blood-brain barrier (BBB), or blood-glioma barrier, which prevents the transport of systemically administered (chemotherapeutic) drugs into the tumor. This study reports the design of dodecamer peptide (G23)-functionalized polydopamine (pD)-coated curcumin-loaded zein nanoparticles (CUR-ZpD-G23 NPs) that efficiently traversed the BBB, and delivered curcumin to glioblastoma cells. The NPs enhanced the cellular uptake of curcumin by C6 glioma cells compared to free curcumin, and showed high penetration into 3D tumor spheroids. Functionalization of the NPs with G23 stimulated BBB crossing and tumor spheroid penetration. Moreover, the NPs markedly inhibited proliferation and migration and induced cell death in liquid and soft agar models of C6 glioma cell growth. Fluorescence microscopy and flow cytometry studies showed that the CUR-ZpD-G23 NPs increased cellular ROS production and induced apoptosis of C6 glioma cells. Following in vivo intravenous injection in zebrafish, ZpD-G23 NPs demonstrated the ability to circulate, which is a first prerequisite for their use in targeted drug delivery. In conclusion, zein-polydopamine-G23 NPs show potential as a drug delivery platform for therapy of GBM, which requires further validation in in vivo glioblastoma models.

RNA Therapeutics: How Far Have We Gone?

In recent years, the RNA molecule became one of the most promising targets for therapeutic intervention. Currently, a large number of RNA-based therapeutics are being investigated both at the basic research level and in late-stage clinical trials. Some of them are even already approved for treatment. RNA-based approaches can act at pre-mRNA level (by splicing modulation/correction using antisense oligonucleotides or U1snRNA vectors), at mRNA level (inhibiting gene expression by siRNAs and antisense oligonucleotides) or at DNA level (by editing mutated sequences through the use of CRISPR/Cas). Other RNA approaches include the delivery of in vitro transcribed (IVT) mRNA or the use of oligonucleotides aptamers. Here we review these approaches and their translation into clinics trying to give a brief overview also on the difficulties to its application as well as the research that is being done to overcome them.

Aurora kinase B siRNA-loaded lactoferrin nanoparticles potentiate the efficacy of temozolomide in treating glioblastoma

Aim: To investigate the efficacy of lactoferrin nanoparticles (LfNPs) in delivering siRNA across the blood–brain barrier to treat glioblastoma multiforme (GBM) and with an additional objective of potentiation of conventional temozolomide (TMZ) chemotherapy. Methods: Aurora kinase B (AKB) siRNA-loaded nanoparticles (AKB–LfNPs) were prepared with milk protein, lactoferrin, by water in oil emulsion method. AKB–LfNPs were tested in cell lines and in GBM orthotopic mouse model with and without TMZ treatment. Results: AKB silencing, cytotoxicity and cell cycle arrest by these LfNPs were shown to be effective on GL261 cells. Tumor growth was significantly lower in AKB–LfNPs alone and in combination with TMZ treated mice and increased the survival by 2.5-times. Conclusion: Treatment of AKB–LfNPs to GBM mice improves life expectancy and has potential to combine with conventional chemotherapy.

A ribonucleoprotein octamer for targeted siRNA delivery

Hurdles in cell-specific delivery of small interfering RNA (siRNA) in vivo hinder the clinical translation of RNA interference (RNAi). A fundamental problem concerns conflicting requirements for the design of the delivery vehicles: cationic materials facilitate cargo condensation and endosomolysis, yet hinder in vivo targeting and colloidal stability. Here, we describe a self-assembled, compact (~30 nm) and biocompatible ribonucleoprotein-octamer nanoparticle that achieves endosomal destabilization and targeted delivery. The protein octamer consists of a poly(ethylene glycol) scaffold, a sterically masked endosomolytic peptide and a double-stranded RNA-binding domain, providing a discrete number of siRNA loading sites and a high siRNA payload (>30 wt%), and offering flexibility in both siRNA and targeting-ligand selection. We show that a ribonucleoprotein octamer against the polo-like kinase 1 gene and bearing a ligand that binds to prostate-specific membrane antigen leads to efficient gene silencing in prostate tumour cells in vitro and when intravenously injected in mouse models of prostate cancer. The octamer's versatile nanocarrier design should offer opportunities for the clinical translation of therapies based on intracellularly acting biologics.

Nanotechnology-Based Strategies for siRNA Brain Delivery for Disease Therapy

Small interfering RNA (siRNA)-based gene silencing technology has demonstrated significant potential for treating brain-associated diseases. However, effective and safe systemic delivery of siRNA into the brain remains challenging because of biological barriers such as enzymatic degradation, short circulation lifetime, the blood-brain barrier (BBB), insufficient tissue penetration, cell endocytosis, and cytosolic transport. Nanotechnology offers intriguing potential for addressing these challenges in siRNA brain delivery in conjunction with chemical and biological modification strategies. In this review, we outline the challenges of systemic delivery of siRNA-based therapy for brain diseases, highlight recent advances in the development and engineering of siRNA nanomedicines for various brain diseases, and discuss our perspectives on this exciting research field for siRNA-based therapy towards more effective brain disease therapy.

siRNA delivery using polyelectrolyte-gold nanoassemblies in neuronal cells for BACE1 gene silencing

Small interfering RNA (siRNA) mediated RNA interference is a versatile therapeutic tool for many intractable genetic disorders. Various nanoassemblies specifically designed to deliver the siRNAs could be utilized for efficient siRNA delivery which is one of the major concern for the success of this therapeutic. Thus, in the present study, polyelectrolyte-gold nanoassemblies (PE-Gold NAs) were selected for siRNA delivery of an in vitro verified siRNA. Three different polyelectrolytes (polyethyleneimine, citraconic anhydride modified poly (allylamine) hydrochloride and poly l-arginine) were used to formulate the PE-Gold NAs using the layer-by-layer technique. Successful physico-chemical characterizations of these PE-Gold NAs were performed using UV-Visible, FTIR, ¹H-NMR spectroscopies, XRD, TEM, DLS and Zeta potential measurements. In vitro studies for the cytotoxicity, the uptake of these nanoassemblies and the gene silencing were carried out using these PE-Gold NAs in N2a and NB4 1A3 (murine neuronal) cell lines. The three selected PE-Gold NAs showed significant BACE1 (β-site APP cleaving enzyme 1) gene silencing (50-60%). This work demonstrates the potential of PE-Gold NAs to deliver siRNA targeting BACE1 in neuronal cells. Finally, it was concluded that different polyelectrolytes used in the PE-Gold NAs achieve different gene silencing due to the variation in their delivery efficiencies.

Poly(glycerol methacrylate)-based degradable nanoparticles for delivery of small interfering RNA

Nucleic acids therapeutic efficiency is generally limited by their low stability and intracellular bioavailability, and by the toxicity of the carriers used to deliver them to the target sites. Aminated poly(glycerol methacrylate) polymers are biodegradable and pH-sensitive polymers that have been used previously to deliver antisense oligonucleotide and show high transfection efficiency. The purpose of this study is to compare the efficiency and toxicity of aminated linear poly(glycerol methacrylate) (ALT) biodegradable polymer to the most commonly used cationic degradable (i.e. chitosan) and non-degradable (i.e. polyethylenimine (PEI)) polymers for delivery of short interfering RNA (siRNA). ALT, PEI and chitosan polymers were able to form nanosized particles with siRNA. Size, size-distribution and zeta-potential were measured over a wide range of nitrogen-to-phosphate (N/P) ratios, and the stability of the formed nanoparticles in saline and upon freeze-drying was also assessed. No significant cytotoxicity at the range of the tested concentrations of ALT and chitosan nanoparticles was observed, whereas the non-degradable PEI showed significant toxicity in huh-7 hepatocyte-derived carcinoma cell line. The safety profiles of the degradable polymers (ALT and chitosan) over non-degradable PEI were demonstrated in vitro and in vivo. In addition, ALT nanoparticles were able to deliver siRNA in vivo with significantly higher efficiency than chitosan nanoparticles. The results in the present study give evidence of the great implications of ALT nanoparticles in biomedical applications due to their biocompatibility, low cytotoxicity, high stability and simple preparation method.

Polyphosphoester nanoparticles as biodegradable platform for delivery of multiple drugs and siRNA

Delivery of multiple therapeutics and/or diagnostic agents to diseased tissues is challenging and necessitates the development of multifunctional platforms. Among the various strategies for design of multifunctional nanocarriers, biodegradable polyphosphoester (PPE) polymers have been recently synthesized via a rapid and simple synthetic strategy. In addition, the chemical structure of the polymer could be tuned to form nanoparticles with varying surface chemistries and charges, which have shown exceptional safety and biocompatibility as compared to several commercial agents. The purpose of this study was to exploit a mixture of PPE nanoparticles of cationic and neutral surface charges for multiple delivery of anticancer drugs (ie, sorafenib and paclitaxel) and nucleic acids (ie, siRNA). Cationic PPE polymers could efficiently complex siRNA, and the stability of the nanoparticles could be maintained in physiological solutions and upon freeze-drying and were able to deliver siRNA in vivo when injected intravenously in mice. Commercially available cationic polyethylenimine polymer had LD50 of ca. 61.7 mg/kg in mice, whereas no animal died after injection of the cationic PPE polymer at a dose of >130 mg/kg. Neutral PPE nanoparticles were able to encapsulate two hydrophobic drugs, namely, sorafenib and paclitaxel, which are commonly used for the treatment of hepatocellular carcinoma. Mixing the neutral and cationic PPE nanoparticles did not result in any precipitation, and the size characteristics of both types of nanoparticles were maintained. Hence, PPE polymers might have potential for the delivery of multiple drugs and diagnostic agents to diseased tissues via simple synthesis of the individual polymers and assembly into nanoparticles that can host several drugs while being mixed in the same administration set, which is of importance for industrial and clinical development.

Functional peptides for siRNA delivery

siRNA is considered as a potent therapeutic agent because of its high specificity and efficiency in suppressing genes that are overexpressed during disease development. For nearly two decades, a significant amount of efforts has been dedicated to bringing the siRNA technology into clinical uses. However, only limited success has been achieved to date, largely due to the lack of a cell type-specific, safe, and efficient delivery technology to carry siRNA into the target cells' cytosol where RNA interference takes place. Among the emerging candidate nanocarriers for siRNA delivery, peptides have gained popularity because of their structural and functional diversity. A variety of peptides have been discovered for their ability to translocate siRNA into living cells via different mechanisms such as direct penetration through the cellular membrane, endocytosis-mediated cell entry followed by endosomolysis, and receptor-mediated uptake. This review is focused on the multiple roles played by peptides in siRNA delivery, such as membrane penetration, endosome disruption, targeting, as well as the combination of these functionalities.

Genetic Substrate Reduction Therapy: A Promising Approach for Lysosomal Storage Disorders

Lysosomal storage diseases are a group of rare genetic disorders characterized by the accumulation of storage molecules in late endosomes/lysosomes. Most of them result from mutations in genes encoding for the catabolic enzymes that ensure intralysosomal digestion. Conventional therapeutic options include enzyme replacement therapy, an approach targeting the functional loss of the enzyme by injection of a recombinant one. Even though this is successful for some diseases, it is mostly effective for peripheral manifestations and has no impact on neuropathology. The development of alternative therapeutic approaches is, therefore, mandatory, and striking innovations including the clinical development of pharmacological chaperones and gene therapy are currently under evaluation. Most of them, however, have the same underlying rationale: an attempt to provide or enhance the activity of the missing enzyme to re-establish substrate metabolism to a level that is consistent with a lack of progression and/or return to health. Here, we will focus on the one approach which has a different underlying principle: substrate reduction therapy (SRT), whose uniqueness relies on the fact that it acts upstream of the enzymatic defect, decreasing storage by downregulating its biosynthetic pathway. Special attention will be given to the most recent advances in the field, introducing the concept of genetic SRT (gSRT), which is based on the use of RNA-degrading technologies (RNA interference and single stranded antisense oligonucleotides) to promote efficient substrate reduction by decreasing its synthesis rate.