Subtle changes to polymer structure and degradation mechanism enable highly effective nanoparticles for siRNA and DNA delivery to human brain cancer

Poly(β-aminoester) Physicochemical Properties Govern the Delivery of siRNA from Electrostatically Assembled Coatings

Localized short interfering RNA (siRNA) therapy has the potential to drive high-specificity molecular-level treatment of a variety of disease states. Unfortunately, effective siRNA therapy suffers from several barriers to its intracellular delivery. Thus, drug delivery systems that package and control the release of therapeutic siRNAs are necessary to overcome these obstacles to clinical translation. Layer-by-layer (LbL) electrostatic assembly of thin film coatings containing siRNA and protonatable, hydrolyzable poly(β-aminoester) (PBAE) polymers is one such drug delivery strategy. However, the impact of PBAE physicochemical properties on the transfection efficacy of siRNA released from LbL thin film coatings has not been systematically characterized. In this study, we investigate the siRNA transfection efficacy of four structurally similar PBAEs in vitro. We demonstrate that small changes in structure yield large changes in physicochemical properties, such as hydrophobicity, pKa, and amine chemical structure, driving differences in the interactions between PBAEs and siRNA in polyplexes and in LbL thin film coatings for wound dressings. In our polymer set, Poly3 forms the most stable interactions with siRNA (Keff,w/w = 0.298) to slow release kinetics and enhance transfection of reporter cells in both colloidal and thin film coating approaches. This is due to its unique physiochemical properties: high hydrophobicity (clog P = 7.86), effective pKa closest to endosomal pH (pKa = 6.21), and high cooperativity in buffering (nhill = 7.2). These properties bestow Poly3 with enhanced endosomal buffering and escape properties. Taken together, this work elucidates the connections between small changes in polymer structure, emergent properties, and polyelectrolyte theory to better understand PBAE transfection efficacy.

Nontoxic, Biodegradable Hyperbranched Poly(β-amino ester)s for Efficient siRNA Delivery and Gene Silencing

RNA interference (RNAi)-mediated gene silencing is a promising therapeutic approach to treat various diseases, but safe and efficient delivery remains a major challenge to its clinical application. Non-viral gene vectors, such as poly(β-amino esters) (pBAEs), have emerged as a potential candidate due to their biodegradability, low toxicity profile, ease of synthesis, and high gene transfection efficiency for both DNA and siRNA delivery. However, achieving significant gene silencing using pBAEs often requires a large amount of polymer carrier (with polymer/siRNA weight ratio >100) or high siRNA dose (>100 nM), which might potentially exacerbate toxicity concerns during delivery. To overcome these barriers, we designed and optimized a series of hyperbranched pBAEs capable of efficiently condensing siRNA and achieving excellent silencing efficiency at a lower polymer/siRNA weight ratio (w/w) and siRNA dose. Through modulation of monomer combinations and branching density, we identified the top-performing hyperbranched pBAEs, named as h(A2B3)-1, which possess good siRNA condensation ability, low cytotoxicity, and high cellular uptake efficiency. Compared with Lipofectamine 2000, h(A2B3)-1 achieved lower cytotoxicity and higher siRNA silencing efficiency in HeLa cells at a polymer/siRNA weight ratio of 30 and 30 nM siRNA dose. Notably, h(A2B3)-1 enhanced the gene uptake in primary neural cells and effectively silenced the target gene in hard-to-transfect primary cortical neurons and oligodendrocyte progenitor cells, with gene knockdown efficiencies of 34.8 and 53.4% respectively. By incorporating a bioreducible disulfide compartment into the polymer backbone, the cytocompatibility of the h(A2B3)-1 was greatly enhanced while maintaining their good transfection efficiency. Together, the low cytotoxicity and high siRNA transfection efficiency of hyperbranched h(A2B3)-1 in this study demonstrated their great potential as a non-viral gene vector for efficient siRNA delivery and RNAi-mediated gene silencing. This provides valuable insight into the future development of safe and efficient non-viral siRNA delivery systems as well as their translation into clinical applications.

Toward low-cost gene therapy: mRNA-based therapeutics for treatment of inherited retinal diseases

Inherited retinal diseases (IRDs) stem from genetic mutations that result in vision impairment. Gene therapy shows promising therapeutic potential, exemplified by the encouraging initial results with voretigene neparvovec. Nevertheless, the associated costs impede widespread access, particularly in low-to-middle income countries. The primary challenge remains: how can we make these therapies globally affordable? Leveraging advancements in mRNA therapies might offer a more economically viable alternative. Furthermore, transitioning to nonviral delivery systems could provide a dual benefit of reduced costs and increased scalability. Relevant stakeholders must collaboratively devise and implement a research agenda to realize the potential of mRNA strategies in equitable access to treatments to prevent vision loss.

Biomaterial-Mediated Genetic Reprogramming of Merkel Cell Carcinoma and Melanoma Leads to Targeted Cancer Cell Killing In Vitro and In Vivo

Tumor immunotherapy is a promising anticancer strategy; however, tumor cells may employ resistance mechanisms, including downregulation of major histocompatibility complex (MHC) molecules to avoid immune recognition. Here, we investigate reprogramming nanoparticles (NPs) that deliver immunostimulatory genes to enhance immunotherapy and address defective antigen presentation in skin cancer in vitro and in vivo. We use a modular poly(beta-amino ester) (PBAE)-based NP to deliver DNA encoding 4-1BBL, IL-12, and IFNγ to reprogram human Merkel cell carcinoma (MCC) cells in vitro and mouse melanoma tumors in vivo to drive adaptive antitumor immune responses. Optimized NP formulations delivering 4-1BBL/IL-12 or 4-1BBL/IL-12/IFNγ DNA successfully transfect MCC and melanoma cells in vitro and in vivo, respectively, resulting in IFNγ-driven upregulation of MHC class I and II molecules on cancer cells. These NPs reprogram the tumor immune microenvironment (TIME) and elicit strong T-cell-driven immune responses, leading to cancer cell killing and T-cell proliferation in vitro and slowing tumor growth and improving survival rates in vivo. Based on expected changes to the tumor immune microenvironment, particularly the importance of IFNγ to the immune response and driving both T-cell function and exhaustion, next-generation NPs codelivering IFNγ were designed. These offered mixed benefits, exchanging improved polyfunctionality for increased T-cell exhaustion and demonstrating higher systemic toxicity in vivo. Further profiling of the immune response with these NPs provides insight into T-cell exhaustion and polyfunctionality induced by different formulations, providing a greater understanding of this immunotherapeutic strategy.

Poly(β-amino ester)s-based nanovehicles: Structural regulation and gene delivery

The first poly(β-amino) esters (PβAEs) were synthesized more than 40 years ago. Since 2000, PβAEs have been found to have excellent biocompatibility and the capability of ferrying gene molecules. Moreover, the synthesis process of PβAEs is simple, the monomers are readily available, and the polymer structure can be tailored to meet different gene delivery needs by adjusting the monomer type, monomer ratio, reaction time, etc. Therefore, PβAEs are a promising class of non-viral gene vector materials. This review paper presents a comprehensive overview of the synthesis and correlated properties of PβAEs and summarizes the progress of each type of PβAE for gene delivery. The review focuses in particular on the rational design of PβAE structures, thoroughly discusses the correlations between intrinsic structure and effect, and then finishes with the applications and perspectives of PβAEs.

Biomaterial-based gene therapy

Gene therapy, a medical approach that involves the correction or replacement of defective and abnormal genes, plays an essential role in the treatment of complex and refractory diseases, such as hereditary diseases, cancer, and rheumatic immune diseases. Nucleic acids alone do not easily enter the target cells due to their easy degradation in vivo and the structure of the target cell membranes. The introduction of genes into biological cells is often dependent on gene delivery vectors, such as adenoviral vectors, which are commonly used in gene therapy. However, traditional viral vectors have strong immunogenicity while also presenting a potential infection risk. Recently, biomaterials have attracted attention for use as efficient gene delivery vehicles, because they can avoid the drawbacks associated with viral vectors. Biomaterials can improve the biological stability of nucleic acids and the efficiency of intracellular gene delivery. This review is focused on biomaterial-based delivery systems in gene therapy and disease treatment. Herein, we review the recent developments and modalities of gene therapy. Additionally, we discuss nucleic acid delivery strategies, with a focus on biomaterial-based gene delivery systems. Furthermore, the current applications of biomaterial-based gene therapy are summarized.

Cationic Polymers as Transfection Reagents for Nucleic Acid Delivery

Nucleic acid therapy can achieve lasting and even curative effects through gene augmentation, gene suppression, and genome editing. However, it is difficult for naked nucleic acid molecules to enter cells. As a result, the key to nucleic acid therapy is the introduction of nucleic acid molecules into cells. Cationic polymers are non-viral nucleic acid delivery systems with positively charged groups on their molecules that concentrate nucleic acid molecules to form nanoparticles, which help nucleic acids cross barriers to express proteins in cells or inhibit target gene expression. Cationic polymers are easy to synthesize, modify, and structurally control, making them a promising class of nucleic acid delivery systems. In this manuscript, we describe several representative cationic polymers, especially biodegradable cationic polymers, and provide an outlook on cationic polymers as nucleic acid delivery vehicles.

Nucleic acid drug vectors for diagnosis and treatment of brain diseases

Nucleic acid drugs have the advantages of rich target selection, simple in design, good and enduring effect. They have been demonstrated to have irreplaceable superiority in brain disease treatment, while vectors are a decisive factor in therapeutic efficacy. Strict physiological barriers, such as degradation and clearance in circulation, blood-brain barrier, cellular uptake, endosome/lysosome barriers, release, obstruct the delivery of nucleic acid drugs to the brain by the vectors. Nucleic acid drugs against a single target are inefficient in treating brain diseases of complex pathogenesis. Differences between individual patients lead to severe uncertainties in brain disease treatment with nucleic acid drugs. In this Review, we briefly summarize the classification of nucleic acid drugs. Next, we discuss physiological barriers during drug delivery and universal coping strategies and introduce the application methods of these universal strategies to nucleic acid drug vectors. Subsequently, we explore nucleic acid drug-based multidrug regimens for the combination treatment of brain diseases and the construction of the corresponding vectors. In the following, we address the feasibility of patient stratification and personalized therapy through diagnostic information from medical imaging and the manner of introducing contrast agents into vectors. Finally, we take a perspective on the future feasibility and remaining challenges of vector-based integrated diagnosis and gene therapy for brain diseases.

Poly (beta-amino ester) as an in vivo nanocarrier for therapeutic nucleic acids

Therapeutic nucleic acids are an emerging class of therapy for treating various diseases through immunomodulation, protein replacement, gene editing, and genetic engineering. However, they need a vector to effectively and safely reach the target cells. Most gene and cell therapies rely on ex vivo gene delivery, which is laborious, time-consuming, and costly; therefore, devising a systematic vector for effective and safe in vivo delivery of therapeutic nucleic acids is required to target the cells of interest in an efficient manner. Synthetic nanoparticle vector poly beta amino ester (PBAE), a class of degradable polymer, is a promising candidate for in vivo gene delivery. PBAE is considered the most potent in vivo vector due to its excellent transfection performance and biodegradability. PBAE nanoparticles showed tunable charge density, diverse structural characteristics, excellent encapsulation capacity, high stability, stimuli-responsive release, site-specific delivery, potent binding to nucleic acids, flexible binding ability to various conjugates, and effective endosomal escape. These unique properties of PBAE are an essential contribution to in vivo gene delivery. The current review discusses each of the components used for PBAE synthesis and the impact of various environmental and physicochemical factors of the body on PBAE nanocarrier.

Synthesis and Characterization of Poly (β-amino Ester) and Applied PEGylated and Non-PEGylated Poly (β-amino ester)/Plasmid DNA Nanoparticles for Efficient Gene Delivery

Polymer-based nanocarriers require extensive knowledge of their chemistries to learn functionalization strategies and understand the nature of interactions that they establish with biological entities. In this research, the poly (β-amino ester) (PβAE-447) was synthesized and characterized, aimed to identify the influence of some key parameters in the formulation process. Initially; PβAE-447 was characterized for aqueous solubility, swelling capacity, proton buffering ability, and cytotoxicity study before nanoparticles formulation. Interestingly, the polymer-supported higher cell viability than the Polyethylenimine (PEI) at 100 μg/ml. PβAE-447 complexed with GFP encoded plasmid DNA (pGFP) generated nanocarriers of 184 nm hydrodynamic radius (+7.42 mV Zeta potential) for cell transfection. Transfection assays performed with PEGylated and lyophilized PβAE-447/pDNA complexes on HEK-293, BEAS-2B, and A549 cell lines showed better transfection than PEI. The outcomes toward A549 cells (above 66%) showed the highest transfection efficiency compared to the other cell lines. Altogether, these results suggested that characterizing physicochemical properties pave the way to design a new generation of PβAE-447 for gene delivery.

Role of Polymeric Local Drug Delivery in Multimodal Treatment of Malignant Glioma: A Review

Malignant gliomas (MGs) are the most common and devastating primary brain tumor. At present, surgical interventions, radiotherapy, and chemotherapy are only marginally effective in prolonging the life expectancy of patients with MGs. Inherent heterogeneity, aggressive invasion and infiltration, intact physical barriers, and the numerous mechanisms underlying chemotherapy and radiotherapy resistance contribute to the poor prognosis for patients with MGs. Various studies have investigated methods to overcome these obstacles in MG treatment. In this review, we address difficulties in MG treatment and focus on promising polymeric local drug delivery systems. In contrast to most local delivery systems, which are directly implanted into the residual cavity after intratumoral injection or the surgical removal of a tumor, some rapidly developing and promising nanotechnological methods—including surface-decorated nanoparticles, magnetic nanoparticles, and focused ultrasound assist transport—are administered through (systemic) intravascular injection. We also discuss further synergistic and multimodal strategies for heightening therapeutic efficacy. Finally, we outline the challenges and therapeutic potential of these polymeric drug delivery systems.

Non-viral nanoparticles for RNA interference: Principles of design and practical guidelines

Ribonucleic acid interference (RNAi) is an innovative treatment strategy for a myriad of indications. Non-viral synthetic nanoparticles (NPs) have drawn extensive attention as vectors for RNAi due to their potential advantages, including improved safety, high delivery efficiency and economic feasibility. However, the complex natural process of RNAi and the susceptible nature of oligonucleotides render the NPs subject to particular design principles and requirements for practical fabrication. Here, we summarize the requirements and obstacles for fabricating non-viral nano-vectors for efficient RNAi. To address the delivery challenges, we discuss practical guidelines for materials selection and NP synthesis in order to maximize RNA encapsulation efficiency and protection against degradation, and to facilitate the cytosolic release of oligonucleotides. The current status of clinical translation of RNAi-based therapies and further perspectives for reducing the potential side effects are also reviewed.

Poly(amino ester)-Based Polymers for Gene and Drug Delivery Systems and Further Application toward Cell Culture System

Various synthetic polymers based on poly(amino ester) (PAE) are suggested as candidates for gene and drug delivery owing to their pH-responsiveness, which contributes to efficient delivery performance. PAE-based pH-responsive polymers are more biodegradable and hydrophilic than other types of pH-responsive polymers. The functionality of PAE-based polymers can be reinforced by using different chemical modifications to improve the efficiency of gene and drug delivery. Additionally, PAE-based polymers are used in many ways in the biomedical field, such as in transdermal delivery and stem cell culture systems. Here, the recent novel PAE-based polymers designed for gene and drug delivery systems along with their further applications toward adult stem cell culture systems are reviewed. The synthetic tactics are contemplated and pros and cons of each type of polymer are analyzed, and detailed examples of the different types are analyzed.

Polyplex-Loaded Hydrogels for Local Gene Delivery to Human Dermal Fibroblasts

Impaired cutaneous healing leading to chronic wounds affects between 2 and 6% of the total population in most developed countries and it places a substantial burden on healthcare budgets. Current treatments involving antibiotic dressings and mechanical debridement are often not effective, causing severe pain, emotional distress, and social isolation in patients for years or even decades, ultimately resulting in limb amputation. Alternatively, gene therapy (such as mRNA therapies) has emerged as a viable option to promote wound healing through modulation of gene expression. However, protecting the genetic cargo from degradation and efficient transfection into primary cells remain significant challenges in the push to clinical translation. Another limiting aspect of current therapies is the lack of sustained release of drugs to match the therapeutic window. Herein, we have developed an injectable, biodegradable and cytocompatible hydrogel-based wound dressing that delivers poly(β-amino ester)s (pBAEs) nanoparticles in a sustained manner over a range of therapeutic windows. We also demonstrate that pBAE nanoparticles, successfully used in previous in vivo studies, protect the mRNA load and efficiently transfect human dermal fibroblasts upon sustained release from the hydrogel wound dressing. This prototype wound dressing technology can enable the development of novel gene therapies for the treatment of chronic wounds.

Small interfering RNA (siRNA) to target genes and molecular pathways in glioblastoma therapy: Current status with an emphasis on delivery systems

Glioblastoma multiforme (GBM) is one of the worst brain tumors arising from glial cells, causing many deaths annually. Surgery, chemotherapy, radiotherapy and immunotherapy are used for GBM treatment. However, GBM is still an incurable disease, and new approaches are required for its successful treatment. Because mutations and amplifications occurring in several genes are responsible for the progression and aggressive behavior of GBM cells, genetic approaches are of great importance in its treatment. Small interfering RNA (siRNA) is a new emerging tool to silence the genes responsible for disease progression, particularly cancer. SiRNA can be used for GBM treatment by down-regulating genes such as VEGF, STAT3, ELTD1 or EGFR. Furthermore, the use of siRNA can promote the chemosensitivity of GBM cells. However, the efficiency of siRNA in GBM is limited via its degradation by enzymes, and its off-targeting effects. SiRNA-loaded carriers, especially nanovehicles that are ligand-functionalized by CXCR4 or angiopep-2, can be used for the protection and targeted delivery of siRNA. Nanostructures can provide a platform for co-delivery of siRNA plus anti-tumor drugs as another benefit. The prepared nanovehicles should be stable and biocompatible in order to be tested in human studies.

Nanoparticle-mediated double-stranded RNA delivery system: A promising approach for sustainable pest management

RNA interference (RNAi) targeting lethal genes in insects has great potential for sustainable crop protection. Compared with traditional double-stranded (ds)RNA delivery systems, nanoparticles such as chitosan, liposomes, and cationic dendrimers offer advantages in delivering dsRNA/small interfering (si)RNA to improve RNAi efficiency, thus promoting the development and practice of RNAi-based pest management strategies. Here, we illustrate the limitations of traditional dsRNA delivery systems, reveal the mechanism of nanoparticle-mediated RNAi, summarize the recent progress and successful applications of nanoparticle-mediated RNAi in pest management, and finally address the prospects of nanoparticle-based RNA pesticides.

Polymeric nanoparticles for RNA delivery

As exemplified by recent clinical approval of RNA drugs including the latest COVID-19 mRNA vaccines, RNA therapy has demonstrated great promise as an emerging medicine. Central to the success of RNA therapy is the delivery of RNA molecules into the right cells at the right location. While the clinical success of nanotechnology in RNA therapy has been limited to lipid-based nanoparticles currently, polymers, due to their tunability and robustness, have also evolved as a class of promising material for the delivery of various therapeutics including RNAs. This article overviews different types of polymers used in RNA delivery and the methods for the formulation of polymeric nanoparticles and highlights recent progress of polymeric nanoparticle-based RNA therapy.

Poly(beta-amino ester)s as gene delivery vehicles: challenges and opportunities

INTRODUCTION

Gene delivery technologies are being developed for an increasing number of biomedical applications, with delivery vehicles including viruses and non-viral materials. Among biomaterials used for non-viral gene delivery, poly(beta-amino ester)s (PBAEs), a class of synthetic, biodegradable polymers, have risen as a leading gene delivery vehicle that has been used for multiple applications in vitro and in vivo.

AREAS COVERED

This review summarizes the key properties of PBAEs and their development, including a discussion of the advantages and disadvantages of PBAEs for gene delivery applications. The use of PBAEs to improve the properties of other drug delivery vehicles is also summarized.

EXPERT OPINION

PBAEs are designed to have multiple characteristics that are ideal for gene delivery, including their reversible positive charge, which promotes binding to nucleic acids as well as imparting high buffering capacity, and their rapid degradability under mild conditions. Simultaneously, some of their properties also lead to nanoparticle instability and low transfection efficiency in physiological environments. The ease with which PBAEs can be chemically modified as well as non-covalently blended with other materials, however, allows them to be customized specifically to overcome delivery barriers for varied applications.

Poly(ethylene glycol)-Poly(beta-amino ester)-Based Nanoparticles for Suicide Gene Therapy Enhance Brain Penetration and Extend Survival in a Preclinical Human Glioblastoma Orthotopic Xenograft Model

Glioblastoma (GBM) is the most devastating brain cancer, and cures remain elusive with currently available neurosurgical, pharmacological, and radiation approaches. While retrovirus- and adenovirus-mediated suicide gene therapy using DNA encoding herpes simplex virus-thymidine kinase (HSV-tk) and prodrug ganciclovir has been suggested as a promising strategy, a nonviral approach for treatment in an orthotopic human primary brain tumor model has not previously been demonstrated. Delivery challenges include nanoparticle penetration through brain tumors, efficient cancer cell uptake, endosomal escape to the cytosol, and biodegradability. To meet these challenges, we synthesized poly(ethylene glycol)-modified poly(beta-amino ester) (PEG-PBAE) polymers to improve extracellular delivery and coencapsulated plasmid DNA with end-modified poly(beta-amino ester) (ePBAE) polymers to improve intracellular delivery as well. We created and evaluated a library of PEG-PBAE/ePBAE nanoparticles (NPs) for effective gene therapy against two independent primary human stem-like brain tumor initiating cells, a putative target to prevent GBM recurrence. The optimally engineered PEG-PBAE/ePBAE NP formulation demonstrated 54 and 82% transfection efficacies in GBM1A and BTIC375 cells respectively, in comparison to 37 and 66% for optimized PBAE NPs without PEG. The leading PEG-PBAE NP formulation also maintained sub-250 nm particle size up to 5 h, while PBAE NPs without PEG showed aggregation over time to micrometer-sized complexes. The comparative advantage demonstrated in vitro successfully translated into improved in vivo diffusion, with a higher amount of PEG-PBAE NPs penetrating to a distance of 2 mm from the injection site. A significant increase in median survival from 53.5 to 67 days by PEG-PBAE/pHSV-tk NP and systemic ganciclovir treatment compared to a control group in orthotopic murine model of human glioblastoma demonstrates the potential of PEG-PBAE-based NPs as an effective gene therapy platform for the treatment of human brain tumors.

Cancer-Targeting Nanoparticles for Combinatorial Nucleic Acid Delivery

Nucleic acids are a promising type of therapeutic for the treatment of a wide range of conditions, including cancer, but they also pose many delivery challenges. For efficient and safe delivery to cancer cells, nucleic acids must generally be packaged into a vehicle, such as a nanoparticle, that will allow them to be taken up by the target cells and then released in the appropriate cellular compartment to function. As with other types of therapeutics, delivery vehicles for nucleic acids must also be designed to avoid unwanted side effects; thus, the ability of such carriers to target their cargo to cancer cells is crucial. Classes of nucleic acids, hurdles that must be overcome for effective intracellular delivery, types of nonviral nanomaterials used as delivery vehicles, and the different strategies that can be employed to target nucleic acid delivery specifically to tumor cells are discussed. Additonally, nanoparticle designs that facilitate multiplexed delivery of combinations of nucleic acids are reviewed.

Topology-assisted, photo-strengthened DNA/siRNA delivery mediated by branched poly(β-amino ester)s via synchronized intracellular kinetics

Photo-degradable, branched poly(β-amino ester)s (BPAE-NB) were developed to mediate topology-assisted trans-membrane gene delivery as well as photo-strengthened intracellular gene release.

Verteporfin-Loaded Anisotropic Poly(Beta-Amino Ester)-Based Micelles Demonstrate Brain Cancer-Selective Cytotoxicity and Enhanced Pharmacokinetics

BACKGROUND

Nanomedicine can improve traditional therapies by enhancing the controlled release of drugs at targeted tissues in the body. However, there still exists disease- and therapy-specific barriers that limit the efficacy of such treatments. A major challenge in developing effective therapies for one of the most aggressive brain tumors, glioblastoma (GBM), is affecting brain cancer cells while avoiding damage to the surrounding healthy brain parenchyma. Here, we developed poly(ethylene glycol) (PEG)-poly(beta-amino ester) (PBAE) (PEG-PBAE)-based micelles encapsulating verteporfin (VP) to increase tumor-specific targeting.

METHODS

Biodegradable, pH-sensitive micelles of different shapes were synthesized via nanoprecipitation using two different triblock PEG-PBAE-PEG copolymers varying in their relative hydrophobicity. The anti-tumor efficacy of verteporfin loaded in these anisotropic and spherical micelles was evaluated in vitro using patient-derived primary GBM cells.

RESULTS

For anisotropic micelles, uptake efficiency was ~100% in GBM cells (GBM1A and JHGBM612) while only 46% in normal human astrocytes (NHA) at 15.6 nM VP (p ≤ 0.0001). Cell killing of GBM1A and JHGBM612 vs NHA was 52% and 77% vs 29%, respectively, at 24 hrs post-treatment of 125 nM VP-encapsulated in anisotropic micelles (p ≤ 0.0001), demonstrating the tumor cell-specific selectivity of VP. Moreover, anisotropic micelles showed an approximately fivefold longer half-life in blood circulation than the analogous spherical micelles in a GBM xenograft model in mice. In this model, micelle accumulation to tumors was significantly greater for anisotropic micelle-treated mice compared to spherical micelle-treated mice at both 8 hrs (~1.8-fold greater, p ≤ 0.001) and 24 hrs (~2.1-fold greater, p ≤ 0.0001).

CONCLUSION

Overall, this work highlights the promise of a biodegradable anisotropic micelle system to overcome multiple drug delivery challenges and enhance efficacy and safety for the treatment of brain cancer.

Engineered nanoparticles for systemic siRNA delivery to malignant brain tumours

Improved delivery materials are needed to enable siRNA transport across biological barriers, including the blood-brain barrier (BBB), to treat diseases like brain cancer. We engineered bioreducible nanoparticles for systemic siRNA delivery to patient-derived glioblastoma cells in an orthotopic mouse tumor model. We first utilized a newly developed biomimetic in vitro model to evaluate and optimize the performance of the engineered bioreducible nanoparticles at crossing the brain microvascular endothelium. We performed transmission electron microscopy imaging which indicated that the engineered nanoparticles are able to cross the BBB endothelium via a vesicular mechanism. The nanoparticle formulation engineered to best cross the BBB model in vitro led to safe delivery across the BBB to the brain in vivo. The nanoparticles were internalized by human brain cancer cells, released siRNA to the cytosol via environmentally-triggered degradation, and gene silencing was obtained both in vitro and in vivo. This study opens new frontiers for the in vitro evaluation and engineering of nanomedicines for delivery to the brain, and reports a systemically administered biodegradable nanocarrier for oligonucleotide delivery to treat glioma.

Lipid nanoparticles for delivery of messenger RNA to the back of the eye

Retinal gene therapy has had unprecedented success in generating treatments that can halt vision loss. However, immunogenic response and long-term toxicity with the use of viral vectors remain a concern. Non-viral vectors are relatively non-immunogenic, scalable platforms that have had limited success with DNA delivery to the eye. Messenger RNA (mRNA) therapeutics has expanded the ability to achieve high gene expression while eliminating unintended genomic integration or the need to cross the restrictive nuclear barrier. Lipid-based nanoparticles (LNPs) remain at the forefront of potent delivery vectors for nucleic acids. Herein, we tested eleven different LNP variants for their ability to deliver mRNA to the back of the eye. LNPs that contained ionizable lipids with low pKa and unsaturated hydrocarbon chains showed the highest amount of reporter gene transfection in the retina. The kinetics of gene expression showed a rapid onset (within 4 h) that persisted for 96 h. The gene delivery was cell-type specific with majority of the expression in the retinal pigmented epithelium (RPE) and limited expression in the Müller glia. LNP-delivered mRNA can be used to treat monogenic retinal degenerative disorders of the RPE. The transient nature of mRNA-based therapeutics makes it desirable for applications that are directed towards retinal reprogramming or genome editing. Overall, non-viral delivery of RNA therapeutics to diverse cell types within the retina can provide transformative new approaches to prevent blindness.

Reducible Branched Ester-Amine Quadpolymers (rBEAQs) Codelivering Plasmid DNA and RNA Oligonucleotides Enable CRISPR/Cas9 Genome Editing

Functional codelivery of plasmid DNA and RNA oligonucleotides in the same nanoparticle system is challenging due to differences in their physical properties as well as their intracellular locations of function. In this study, we synthesized a series of reducible branched ester-amine quadpolymers (rBEAQs) and investigated their ability to coencapsulate and deliver DNA plasmids and RNA oligos. The rBEAQs are designed to leverage polymer branching, reducibility, and hydrophobicity to successfully cocomplex DNA and RNA in nanoparticles at low polymer to nucleic acid w/w ratios and enable high delivery efficiency. We validate the synthesis of this new class of biodegradable polymers, characterize the self-assembled nanoparticles that these polymers form with diverse nucleic acids, and demonstrate that the nanoparticles enable safe, effective, and efficient DNA-siRNA codelivery as well as nonviral CRISPR-mediated gene editing utilizing Cas9 DNA and sgRNA codelivery.

Differentially Branched Ester Amine Quadpolymers with Amphiphilic and pH-Sensitive Properties for Efficient Plasmid DNA Delivery

Development of highly effective nonviral gene delivery vectors for transfection of diverse cell populations remains a challenge despite utilization of both rational and combinatorial driven approaches to nanoparticle engineering. In this work, multifunctional polyesters are synthesized with well-defined branching structures via A2 + B2/B3 + C1 Michael addition reactions from small molecule acrylate and amine monomers and then end-capped with amine-containing small molecules to assess the influence of polymer branching structure on transfection. These Branched poly(Ester Amine) Quadpolymers (BEAQs) are highly effective for delivery of plasmid DNA to retinal pigment epithelial cells and demonstrate multiple improvements over previously reported leading linear poly(beta-amino ester)s, particularly for volume-limited applications where improved efficiency is required. BEAQs with moderate degrees of branching are demonstrated to be optimal for delivery under high serum conditions and low nanoparticle doses further relevant for therapeutic gene delivery applications. Defined structural properties of each polymer in the series, including tertiary amine content, correlated with cellular transfection efficacy and viability. Trends that can be applied to the rational design of future generations of biodegradable polymers are elucidated.

The role of assembly parameters on polyplex poly(beta-amino ester) nanoparticle transfections

Intracellular delivery of nucleic acids to mammalian cells using polyplex nanoparticles (NPs) remains a challenge both in vitro and in vivo, with transfections often suffering from variable efficacy. To improve reproducibility and efficacy of transfections in vitro using a next-generation polyplex transfection material poly(beta-amino ester)s (PBAEs), the influence of multiple variables in the preparation of these NPs on their transfection efficacy was explored. The results indicate that even though PBAE/pDNA polyplex NPs are formed by the self-assembly of polyelectrolytes, their transfection is not affected by the manner in which the components are mixed, facilitating self-assembly in a single step, but timing for self-assembly of 5-20 min is optimal. In addition, even though the biomaterials are biodegradable in water, their efficacy is not affected by up to eight freeze-thaw cycles of the polymer. It was found that there is a greater stability of nucleic acid-complexed polymer as a polyplex nanoparticle compared with free polymer. Finally, by exploring multiple buffer systems, it was identified that utilization of divalent cation magnesium or calcium acetate buffers at pH 5.0 is optimal for transfection using these polymeric materials, boosting transfection several folds compared with monovalent cations. Together, these results can improve the reproducibility and efficacy of PBAE and similar polyplex nanoparticle transfections and improve the robustness of using these biomaterials for bioengineering and biotechnology applications.

Vectors for Glioblastoma Gene Therapy: Viral & Non-Viral Delivery Strategies

Glioblastoma multiforme is the most common and aggressive primary brain tumor. Even with aggressive treatment including surgical resection, radiation, and chemotherapy, patient outcomes remain poor, with five-year survival rates at only 10%. Barriers to treatment include inefficient drug delivery across the blood brain barrier and development of drug resistance. Because gliomas occur due to sequential acquisition of genetic alterations, gene therapy represents a promising alternative to overcome limitations of conventional therapy. Gene or nucleic acid carriers must be used to deliver these therapies successfully into tumor tissue and have been extensively studied. Viral vectors have been evaluated in clinical trials for glioblastoma gene therapy but have not achieved FDA approval due to issues with viral delivery, inefficient tumor penetration, and limited efficacy. Non-viral vectors have been explored for delivery of glioma gene therapy and have shown promise as gene vectors for glioma treatment in preclinical studies and a few non-polymeric vectors have entered clinical trials. In this review, delivery systems including viral, non-polymeric, and polymeric vectors that have been used in glioblastoma multiforme (GBM) gene therapy are discussed. Additionally, advances in glioblastoma gene therapy using viral and non-polymeric vectors in clinical trials and emerging polymeric vectors for glioma gene therapy are discussed.

Poly(β-Amino Esters): Synthesis, Formulations, and Their Biomedical Applications

Poly(β-amino ester) (abbreviated as PBAE or PAE) refers to a polymer synthesized from an acrylate and an amine by Michael addition and has properties inherent to tertiary amines and esters, such as pH responsiveness and biodegradability. The versatility of building blocks provides a library of polymers with miscellaneous physicochemical and mechanical properties. When used alone or together with other materials, PBAEs can be fabricated into different formulations in order to fulfill various requirements in drug delivery (for instance, gene, anticancer drugs, and antimicrobials delivery) and natural complex mimicry (nanochaperones). This progress report discusses the recent developments in design, synthesis, formulations, and applications of PBAEs in biomedical fields and provides a perspective view for the future of the PBAEs.

Influence of PDLA nanoparticles size on drug release and interaction with cells

Polymeric nanoparticles (NPs) are strong candidates for the development of systemic and targeted drug delivery applications. Their size is a determinant property since it defines the NP-cell interactions, drug loading capacity, and release kinetics. Herein, poly(d,l-lactic acid) (PDLA) NPs were produced by the nanoprecipitation method, in which the influence of type and concentration of surfactant as well as PDLA concentration were assessed. The adjustment of these parameters allowed the successful production of NPs with defined medium sizes, ranging from 80 to 460 nm. The surface charge of the different NPs populations was consistently negative. Prednisolone was effectively entrapped and released from NPs with statistically different medium sizes (i.e., 80 or 120 nm). Release profiles indicate that these systems were able to deliver appropriate amounts of drug with potential applicability in the treatment of inflammatory conditions. Both NPs populations were cytocompatible with human endothelial and fibroblastic cells, in the range of concentrations tested (0.187-0.784 mg/mL). However, confocal microscopy revealed that within the range of sizes tested in our experiments, NPs presenting a medium size of 120 nm were able to be internalized in endothelial cells. In summary, this study demonstrates the optimization of the processing conditions to obtain PDLA NPs with narrow size ranges, and with promising performance for the treatment of inflammatory diseases. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 482-493, 2019.

Bacterial tRNase-Based Gene Therapy with Poly(β-Amino Ester) Nanoparticles for Suppressing Melanoma Tumor Growth and Relapse

Here, a novel anticancer gene therapy with a bacterial tRNase gene, colicin D or virulence associated protein C (VapC), is suggested using biodegradable polymeric nanoparticles, such as poly(β-amino esters) (PBAEs) as carriers. These genes are meticulously selected, aiming at inhibiting translation in the recipients by hydrolyzing specific tRNA species. In terms of nanoparticles, out of 9 PBAE formulations, a leading polymer, (polyethylene oxide)₄ -bis-amine end-capped poly(1,4-butanediol diacrylate-co-5-amino-1-pentanol) (B4S5E5), is identified that displays higher gene delivery efficacy to cancer cells compared with the leading commercial reagent Lipofectamine 2000. Interestingly, the B4S5E5 PBAE nanoparticles complexed with colicin D or VapC plasmid DNA induce significant toxicity highly specific to cancer cells by triggering apoptosis. In contrast, the PBAE nanoparticles do not induce these cytotoxic effects in noncancerous cells. In a mouse melanoma model of grafted murine B16-F10 cells, it is demonstrated that treatment with PBAE nanoparticles complexed with these tRNase genes significantly reduces tumor growth rate and delays tumor relapse. Moreover, increased stability of PBAE by PEGylation further enhances the therapeutic effect of tRNase gene treatment and improves survival of animals. This study highlights a nonviral gene therapy that is highly promising for the treatment of cancer.

Verteporfin-Loaded Poly(ethylene glycol)-Poly(beta-amino ester)-Poly(ethylene glycol) Triblock Micelles for Cancer Therapy

Amphiphilic polymers can be used to form micelles to deliver water-insoluble drugs. A biodegradable poly(ethylene glycol) (PEG)-poly(beta-amino ester) (PBAE)-PEG triblock copolymer was developed that is useful for drug delivery. It was shown to successfully encapsulate and pH-dependently release a water-insoluble, small molecule anticancer drug, verteporfin. PEG-PBAE-PEG micelle morphology was also controlled through variations to the hydrophobicity of the central PBAE block of the copolymer in order to evade macrophage uptake. Spherical micelles were 50 nm in diameter, while filamentous micelles were 31 nm in width with an average aspect ratio of 20. When delivered to RAW 264.7 mouse macrophages, filamentous micelles exhibited a 89% drop in cellular uptake percentage and a 5.6-fold drop in normalized geometric mean cellular uptake compared to spherical micelles. This demonstrates the potential of high-aspect-ratio, anisotropically shaped PEG-PBAE-PEG micelles to evade macrophage-mediated clearance. Both spherical and filamentous micelles also showed therapeutic efficacy in human triple-negative breast cancer and small cell lung cancer cells without requiring photodynamic therapy to achieve an anticancer effect. Both spherical and filamentous micelles were more effective in killing lung cancer cells than breast cancer cells at equivalent verteporfin concentrations, while spherical micelles were shown to be more effective than filamentous micelles against both cancer cells. Spherical and filamentous micelles at 5 and 10 μM respective verteporfin concentration resulted in 100% cell killing of lung cancer cells, but both micelles required a higher verteporfin concentration of 20 μM to kill breast cancer cells at the levels of 80% and 50% respectively. This work demonstrates the potential of PEG-PBAE-PEG as a biodegradable, anisotropic drug delivery system as well as the in vitro use of verteporfin-loaded micelles for cancer therapy.

Bioreducible Polymeric Nanoparticles Containing Multiplexed Cancer Stem Cell Regulating miRNAs Inhibit Glioblastoma Growth and Prolong Survival

Despite our growing molecular-level understanding of glioblastoma (GBM), treatment modalities remain limited. Recent developments in the mechanisms of cell fate regulation and nanomedicine provide new avenues by which to treat and manage brain tumors via the delivery of molecular therapeutics. Here, we have developed bioreducible poly(β-amino ester) nanoparticles that demonstrate high intracellular delivery efficacy, low cytotoxicity, escape from endosomes, and promotion of cytosol-targeted environmentally triggered cargo release for miRNA delivery to tumor-propagating human cancer stem cells. In this report, we combined this nanobiotechnology with newly discovered cancer stem cell inhibiting miRNAs to develop self-assembled miRNA-containing polymeric nanoparticles (nano-miRs) to treat gliomas. We show that these nano-miRs effectively intracellularly deliver single and combination miRNA mimics that inhibit the stem cell phenotype of human GBM cells in vitro. Following direct intratumoral infusion, these nano-miRs were found to distribute through the tumors, inhibit the growth of established orthotopic human GBM xenografts, and cooperatively enhance the response to standard-of-care γ radiation. Co-delivery of two miRNAs, miR-148a and miR-296-5p, within the bioreducible nano-miR particles enabled long-term survival from GBM in mice.

Biodegradable Polymeric Nanoparticles for Therapeutic Cancer Treatments

Polymeric nanoparticles have tremendous potential to improve the efficacy of therapeutic cancer treatments by facilitating targeted delivery to a desired site. The physical and chemical properties of polymers can be tuned to accomplish delivery across the multiple biological barriers required to reach diverse subsets of cells. The use of biodegradable polymers as nanocarriers is especially attractive, as these materials can be designed to break down in physiological conditions and engineered to exhibit triggered functionality when at a particular location or activated by an external source. We present how biodegradable polymers can be engineered as drug delivery systems to target the tumor microenvironment in multiple ways. These nanomedicines can target cancer cells directly, the blood vessels that supply the nutrients and oxygen that support tumor growth, and immune cells to promote anticancer immunotherapy.

Biodegradable STING agonist nanoparticles for enhanced cancer immunotherapy

Therapeutic cancer vaccines require adjuvants leading to robust type I interferon and proinflammatory cytokine responses in the tumor microenvironment to induce an anti-tumor response. Cyclic dinucleotides (CDNs), a potent Stimulator of Interferon Receptor (STING) agonist, are currently in phase I trials. However, their efficacy may be limited to micromolar concentrations due to the cytosolic residence of STING in the ER membrane. Here we utilized biodegradable, poly(beta-amino ester) (PBAE) nanoparticles to deliver CDNs to the cytosol leading to robust immune response at >100-fold lower extracellular CDN concentrations in vitro. The leading CDN PBAE nanoparticle formulation induced a log-fold improvement in potency in treating established B16 melanoma tumors in vivo when combined with PD-1 blocking antibody in comparison to free CDN without nanoparticles. This nanoparticle-mediated cytosolic delivery method for STING agonists synergizes with checkpoint inhibitors and has strong potential for enhanced cancer immunotherapy.

A Triple-Fluorophore-Labeled Nucleic Acid pH Nanosensor to Investigate Non-viral Gene Delivery

There is a need for new tools to better quantify intracellular delivery barriers in high-throughput and high-content ways. Here, we synthesized a triple-fluorophore-labeled nucleic acid pH nanosensor for measuring intracellular pH of exogenous DNA at specific time points in a high-throughput manner by flow cytometry following non-viral transfection. By including two pH-sensitive fluorophores and one pH-insensitive fluorophore in the nanosensor, detection of pH was possible over the full physiological range. We further assessed possible correlation between intracellular pH of delivered DNA, cellular uptake of DNA, and DNA reporter gene expression at 24 hr post-transfection for poly-L-lysine and branched polyethylenimine polyplex nanoparticles. While successful transfection was shown to clearly depend on median cellular pH of delivered DNA at the cell population level, surprisingly, on an individual cell basis, there was no significant correlation between intracellular pH and transfection efficacy. To our knowledge, this is the first reported instance of high-throughput single-cell analysis between cellular uptake of DNA, intracellular pH of delivered DNA, and gene expression of the delivered DNA. Using the nanosensor, we demonstrate that the ability of polymeric nanoparticles to avoid an acidic environment is necessary, but not sufficient, for successful transfection.

Highly Branched poly(5-amino-1-pentanol-co-1,4-butanediol diacrylate) for High Performance Gene Transfection

The top-performing linear poly(β-amino ester) (LPAE), poly(5-amino-1-pentanol-co-1,4-butanediol diacrylate) (C32), has demonstrated gene transfection efficiency comparable to viral-mediated gene delivery. Herein, we report the synthesis of a series of highly branched poly(5-amino-1-pentanol-co-1,4-butanediol diacrylate) (HC32) and explore how the branching structure influences the performance of C32 in gene transfection. HC32 were synthesized by an “A2 + B3 + C2” Michal addition strategy. Gaussia luciferase (Gluciferase) and green fluorescent protein (GFP) coding plasmid DNA were used as reporter genes and the gene transfection efficiency was evaluated in human cervical cancer cell line (HeLa) and human recessive dystrophic epidermolysis bullosa keratinocyte (RDEBK) cells. We found that the optimal branching structure led to a much higher gene transfection efficiency in comparison to its linear counterpart and commercial reagents, while preserving high cell viability in both cell types. The branching strategy affected DNA binding, proton buffering capacity and degradation of polymers as well as size, zeta potential, stability, and DNA release rate of polyplexes significantly. Polymer degradation and DNA release rate played pivotal parts in achieving the high gene transfection efficiency of HC32-103 polymers, providing new insights for the development of poly(β-amino ester)s-based gene delivery vectors.

Enhancing oligodendrocyte differentiation by transient transcription activation via DNA nanoparticle-mediated transfection

Current approaches to derive oligodendrocytes from human pluripotent stem cells (hPSCs) need extended exposure of hPSCs to growth factors and small molecules, which limits their clinical application because of the lengthy culture time required and low generation efficiency of myelinating oligodendrocytes. Compared to extrinsic growth factors and molecules, oligodendrocyte differentiation and maturation can be more effectively modulated by regulation of the cell transcription network. In the developing central nervous system (CNS), two basic helix-loop-helix transcription factors, Olig1 and Olig2, are decisive in oligodendrocyte differentiation and maturation. Olig2 plays a critical role in the specification of oligodendrocytes and Olig1 is crucial in promoting oligodendrocyte maturation. Recently viral vectors have been used to overexpress Olig2 and Olig1 in neural stem/progenitor cells (NSCs) to induce the maturation of oligodendrocytes and enhance the remyelination activity in vivo. Because of the safety issues with viral vectors, including the insertional mutagenesis and potential tumor formation, non-viral transfection methods are preferred for clinical translation. Here we report a poly(β-amino ester) (PBAE)-based nanoparticle transfection method to deliver Olig1 and Olig2 into human fetal tissue-derived NSCs and demonstrate efficient oligodendrocyte differentiation following transgene expression of Olig1 and Olig2. This approach is potentially translatable for engineering stem cells to treat injured or diseased CNS tissues.

STATEMENT OF SIGNIFICANCE

Current protocols to derive oligodendrocytes from human pluripotent stem cells (hPSCs) require lengthy culture time with low generation efficiencies of mature oligodendrocytes. We described a new approach to enhance oligodendrocyte differentiation through nanoparticle-mediated transcription modulation. We tested an effective transfection method using cell-compatible poly (β-amino ester) (PBAE)/DNA nanoparticles as gene carrier to deliver transcription factor Olig1 and Olig2 into human fetal tissue-derived neural stem/progenitor cells, and showed efficient oligodendrocyte differentiation following transgene expression of Olig1 and Olig2. We believe that this translatable approach can be applied to many other cell-based regenerative therapies as well.

Continuous microfluidic assembly of biodegradable poly(beta-amino ester)/DNA nanoparticles for enhanced gene delivery

Translation of biomaterial-based nanoparticle formulations to the clinic faces significant challenges including efficacy, safety, consistency and scale-up of manufacturing, and stability during long-term storage. Continuous microfluidic fabrication of polymeric nanoparticles has the potential to alleviate the challenges associated with manufacture, while offering a scalable solution for clinical level production. Poly(beta-amino esters) (PBAE)s are a class of biodegradable cationic polymers that self-assemble with anionic plasmid DNA to form polyplex nanoparticles that have been shown to be effective for transfecting cancer cells specifically in vitro and in vivo. Here, we demonstrate the use of a microfluidic device for the continuous and scalable production of PBAE/DNA nanoparticles followed by lyophilization and long term storage that results in improved in vitro efficacy in multiple cancer cell lines compared to nanoparticles produced by bulk mixing as well as in comparison to widely used commercially available transfection reagents polyethylenimine and Lipofectamine® 2000. We further characterized the nanoparticles using nanoparticle tracking analysis (NTA) to show that microfluidic mixing resulted in fewer DNA-free polymeric nanoparticles compared to those produced by bulk mixing. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1813-1825, 2017.

Brain-Targeted Polymers for Gene Delivery in the Treatment of Brain Diseases

Gene therapies have become a promising strategy for treating neurological disorders, such as brain cancer and neurodegenerative diseases, with the help of molecular biology interpreting the underlying pathological mechanisms. Successful cellular manipulation against these diseases requires efficient delivery of nucleic acids into brain and further into specific neurons or cancer cells. Compared with viral vectors, non-viral polymeric carriers provide a safer and more flexible way of gene delivery, although suffering from significantly lower transfection efficiency. Researchers have been devoted to solving this defect, which is attributed to the multiple barriers existing for gene therapeutics in vivo, such as systemic degradation, blood-brain barrier, and endosome trapping. This review will be mainly focused on systemically administrated brain-targeted polymers developed so far, including PEI, dendrimers, and synthetic polymers with various functions. We will discuss in detail how they are designed to overcome these barriers and how they efficiently deliver therapeutic nucleic acids into targeted cells.

Combinatorial optimization of PEG architecture and hydrophobic content improves ternary siRNA polyplex stability, pharmacokinetics, and potency in vivo

A rationally-designed library of ternary siRNA polyplexes was developed and screened for gene silencing efficacy in vitro and in vivo with the goal of overcoming both cell-level and systemic delivery barriers. [2-(dimethylamino)ethyl methacrylate] (DMAEMA) was homopolymerized or copolymerized (50mol% each) with butyl methacrylate (BMA) from a reversible addition - fragmentation chain transfer (RAFT) chain transfer agent, with and without pre-conjugation to polyethylene glycol (PEG). Both single block polymers were tested as core-forming units, and both PEGylated, diblock polymers were screened as corona-forming units. Ternary siRNA polyplexes were assembled with varied amounts and ratios of core-forming polymers to PEGylated corona-forming polymers. The impact of polymer composition/ratio, hydrophobe (BMA) placement, and surface PEGylation density was correlated to important outcomes such as polyplex size, stability, pH-dependent membrane disruptive activity, biocompatibility, and gene silencing efficiency. The lead formulation, DB4-PDB12, was optimally PEGylated not only to ensure colloidal stability (no change in size by DLS between 0 and 24h) and neutral surface charge (0.139mV) but also to maintain higher cell uptake (>90% positive cells) than the most densely PEGylated particles. The DB4-PDB12 polyplexes also incorporated BMA in both the polyplex core- and corona-forming polymers, resulting in robust endosomolysis and in vitro siRNA silencing (~85% protein level knockdown) of the model gene luciferase across multiple cell types. Further, the DB4-PDB12 polyplexes exhibited greater stability, increased blood circulation time, reduced renal clearance, increased tumor biodistribution, and greater silencing of luciferase compared to our previously-optimized, binary parent formulation following intravenous (i.v.) delivery. This polyplex library approach enabled concomitant optimization of the composition and ratio of core- and corona-forming polymers (indirectly tuning PEGylation density) and identification of a ternary nanomedicine optimized to overcome important siRNA delivery barriers in vitro and in vivo.

Targeted Nanotechnology in Glioblastoma Multiforme

Gliomas, and in particular glioblastoma multiforme, are aggressive brain tumors characterized by a poor prognosis and high rates of recurrence. Current treatment strategies are based on open surgery, chemotherapy (temozolomide) and radiotherapy. However, none of these treatments, alone or in combination, are considered effective in managing this devastating disease, resulting in a median survival time of less than 15 months. The efficiency of chemotherapy is mainly compromised by the blood-brain barrier (BBB) that selectively inhibits drugs from infiltrating into the tumor mass. Cancer stem cells (CSCs), with their unique biology and their resistance to both radio- and chemotherapy, compound tumor aggressiveness and increase the chances of treatment failure. Therefore, more effective targeted therapeutic regimens are urgently required. In this article, some well-recognized biological features and biomarkers of this specific subgroup of tumor cells are profiled and new strategies and technologies in nanomedicine that explicitly target CSCs, after circumventing the BBB, are detailed. Major achievements in the development of nanotherapies, such as organic poly(propylene glycol) and poly(ethylene glycol) or inorganic (iron and gold) nanoparticles that can be conjugated to metal ions, liposomes, dendrimers and polymeric micelles, form the main scope of this summary. Moreover, novel biological strategies focused on manipulating gene expression (small interfering RNA and clustered regularly interspaced short palindromic repeats [CRISPR]/CRISPR associated protein 9 [Cas 9] technologies) for cancer therapy are also analyzed. The aim of this review is to analyze the gap between CSC biology and the development of targeted therapies. A better understanding of CSC properties could result in the development of precise nanotherapies to fulfill unmet clinical needs.

Polymeric nanoparticles as cancer-specific DNA delivery vectors to human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third most deadly cancer in the US, with a meager 5-year survival rate of <20%. Such unfavorable numbers are closely related to the heterogeneity of the disease and the unsatisfactory therapies currently used to manage patients with invasive HCC. Outside of the clinic, gene therapy research is evolving to overcome the poor responses and toxicity associated with standard treatments. The inadequacy of gene delivery vectors, including poor intracellular delivery and cell specificity, are major barriers in the gene therapy field. Herein, we described a non-viral strategy for effective and cancer-specific DNA delivery to human HCC using biodegradable poly(beta-amino ester) (PBAE) nanoparticles (NPs). Varied PBAE NP formulations were evaluated for transfection efficacy and cytotoxicity to a range of human HCC cells as well as healthy human hepatocytes. To address HCC heterogeneity, nine different sources of human HCC cells were utilized. The polymeric NPs composed of 2-((3-aminopropyl)amino) ethanol end-modified poly(1,5-pentanediol diacrylate-co-3-amino-1-propanol) ('536') at a 25 polymer-to-DNA weight-to-weight ratio led to high transfection efficacy to all of the liver cancer lines, but not to hepatocytes. Each individual HCC line had a significantly higher percentage of exogenous gene expression than the healthy liver cells (P<0.01). Notably, this biodegradable end-modified PBAE gene delivery vector was not cytotoxic and maintained the viability of hepatocytes above 80%. In a HCC/hepatocyte co-culture model, in which cancerous and healthy cells share the same micro-environment, 536 25 w/w NPs specifically transfected cancer cells. PBAE NP administration to a subcutaneous HCC mouse model, established with one of the human lines tested in vitro, confirmed effective DNA transfection in vivo. PBAE-based NPs enabled high and preferential DNA delivery to HCC cells, sparing healthy hepatocytes. These biodegradable and liver cancer-selective NPs are a promising technology to deliver therapeutic genes to liver cancer.