Light-mediated activation of siRNA Release in diblock copolymer assemblies for controlled gene silencing

Polymer-lipid hybrid nanomedicines to deliver siRNA in and against glioblastoma cells

Small interfering RNA (siRNA) holds great potential to treat many difficult-to-treat diseases, but its delivery remains the central challenge. This study aimed at investigating the suitability of polymer-lipid hybrid nanomedicines (HNMeds) as novel siRNA delivery platforms for locoregional therapy of glioblastoma. Two HNMed formulations were developed from poly(lactic-co-glycolic acid) polymer and a cationic lipid: 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or 3ß-[N-(N',N'-dimethylaminoethane)-carbamoyl]cholesterol (DC-Chol). After characterization of the HNMeds, a model siRNA was complexed onto their surface to form HNMed/siRNA complexes. The physicochemical properties and siRNA binding ability of complexes were assessed over a range of nitrogen-to-phosphate (N/P) ratios to optimize the formulations. At the optimal N/P ratio of 10, complexes effectively bound siRNA and improved its protection from enzymatic degradation. Using the NIH3T3 mouse fibroblast cell line, DOTAP-based HNMeds were shown to possess higher cytocompatibility in vitro over the DC-Chol-based ones. As proof-of-concept, uptake and bioefficacy of formulations were also assessed in vitro on U87MG human glioblastoma cell line expressing luciferase gene. Complexes were able to deliver anti-luciferase siRNA and induce a remarkable suppression of gene expression. Noteworthy, the effect of DOTAP-based formulation was not only about three-times higher than DC-Chol-based one, but also comparable to lipofectamine model transfection reagent. These findings set the basis to exploit this nanosystem for silencing relevant GB-related genes in further in vitro and in vivo studies.

Multifunctional siRNA/ferrocene/cyclodextrin nanoparticles for enhanced chemodynamic cancer therapy

The therapeutic outcome of chemodynamic therapy (CDT) is greatly hindered by the presence of oxidative damage repair proteins (MTH1) inside cancer cells. These oxidative damage repair proteins detoxify the action of radicals generated by Fenton or Fenton-like reactions. Hence, it is extremely important to develop a simple strategy for the downregulation of MTH1 protein inside cancer cells along with the delivery of metal ions into cancer cells. A one-pot host-guest supramolecular approach for the codelivery of MTH1 siRNA and metal ions into a cancer cell is reported. Our approach involves the fabrication of an inclusion complex between cationic β-cyclodextrin and a ferrocene prodrug, which spontaneously undergoes amphiphilicity-driven self-assembly to form spherical nanoparticles (NPs) having a positively charged surface. The cationic surface of the NPs was then explored for the loading of MTH1 siRNA through electrostatic interactions. Using HeLa cells as a representative example, efficient uptake of the NPs, delivery of MTH1 siRNA and the enhanced CDT of the nanoformulation are demonstrated. This work highlights the potential of the supramolecular approach as a simple yet efficient method for the delivery of siRNA across the cell membrane for enhanced chemodynamic therapy.

Controlled siRNA Release of Nanopolyplex for Effective Targeted Anticancer Therapy in Animal Model

Introduction

Spatiotemporally controlled release of siRNA for anti-tumor therapy poses significant challenges. Near-infrared (NIR) light, known for its exceptional tissue penetration and minimal tissue invasiveness, holds promise as a viable exogenous stimulus for inducing controlled siRNA release in vivo. However, the majority of light-responsive chemical bonds exhibit absorption wavelengths in the ultraviolet (UV) or short-wavelength visible light range.

Methods

To achieve NIR-controlled siRNA release, the study synthesized a UV-sensitive triblock copolymer cRGD-poly(ethylene glycol)-b-poly(aspartic acid ester-5-(2'-(dimethylamino)ethoxy)-2-nitrobenzyl alcohol)-b-polyphenylalanine, abbreviated as cRGD-PEG-PAsp(EDONB)-PPHE. This copolymer is composed of a cRGD-capped PEG block (cRGD-PEG), a poly(aspartate) block modified with cationic moieties through UV-cleavable 2-nitrobenzyl ester bonds [PAsp(EDONB)], and a hydrophobic polyphenylalanine block (PPHE). The cationic amphiphilic polymer cRGD-PEG-PAsp(EDONB)-PPHE can assemble with hydrophobic upconversion nanoparticles (UCNPs) to form a cationic micelle designated as T-UCNP, which subsequently complexes with siRNA to create the final nanopolyplex T-si/UCNP. siRNA-PLK1 was employed to prepare T-PLK1/UCNP nanopolyplex for anti-tumor therapy.

Results

T-PLK1/UCNP not only exhibited outstanding tumor cell targeting through cRGD modification but also achieved 980 nm NIR-controlled PLK1 gene silencing. This was achieved by utilizing the encapsulated UCNPs to convert NIR into UV light, facilitating the cleavage of 2-nitrobenzyl ester bonds. As a result, there was a significant suppression of tumor growth.

Conclusion

The UCNPs-encapsulated nanopolyplex T-si/UCNP, capable of co-delivering siRNA and UCNPs, enables precise NIR-controlled release of siRNA at the tumor site for cancer RNAi therapy. This nanopolyplex can enhance the controllability and safety of RNAi therapy for tumors, and it also holds the potential to serve as a platform for achieving controlled release and activation of other drugs, such as mRNA and DNA.

Two-Photon Light Trigger siRNA Transfection of Cancer Cells Using Non-Toxic Porous Silicon Nanoparticles

The concept of using two-photon excitation in the NIR for the spatiotemporal control of biological processes holds great promise. However, its use for the delivery of nucleic acids has been very scarcely described and the reported procedures are not optimal as they often involve potentially toxic materials and irradiation conditions. This work prepares a simple system made of biocompatible porous silicon nanoparticles (pSiNP) for the safe siRNA photocontrolled delivery and gene silencing in cells upon two-photon excitation. PSiNP are linked to an azobenzene moiety, which possesses a lysine group (pSiNP@ICPES-azo@Lys) to efficiently complex siRNA. Non-linear excitation of the two-photon absorber system (pSiNP) followed by intermolecular energy transfer (FRET) to trans azobenzene moiety, result in the photoisomerization of the azobenzene from trans to cis and in the destabilization of the azobenzene-siRNA complex, thus inducing the delivery of the cargo siRNA to the cytoplasm of cells. Efficient silencing in MCF-7 expressing stable firefly luciferase with siRNAluc against luciferase is observed. Furthermore, siRNA against inhibitory apoptotic protein (IAP) leads to over 70% of MCF-7 cancer cell death. The developed technique using two-photon light allows a unique high spatiotemporally controlled and safe siRNA delivery in cells in few seconds of irradiation.

RNAi therapies: Expanding applications for extrahepatic diseases and overcoming delivery challenges

The era of RNA medicine has become a reality with the success of messenger RNA (mRNA) vaccines against COVID-19 and the approval of several RNA interference (RNAi) agents in recent years. Particularly, therapeutics based on RNAi offer the promise of targeting intractable and previously undruggable disease genes. Recent advances have focused in developing delivery systems to enhance the poor cellular uptake and insufficient pharmacokinetic properties of RNAi therapeutics and thereby improve its efficacy and safety. However, such approach has been mainly achieved via lipid nanoparticles (LNPs) or chemical conjugation with N-Acetylgalactosamine (GalNAc), thus current RNAi therapy has been limited to liver diseases, most likely to encounter liver-targeting limitations. Hence, there is a huge unmet medical need for intense evolution of RNAi therapeutics delivery systems to target extrahepatic tissues and ultimately extend their indications for treating various intractable diseases. In this review, challenges of delivering RNAi therapeutics to tumors and major organs are discussed, as well as their transition to clinical trials. This review also highlights innovative and promising preclinical RNAi-based delivery platforms for the treatment of extrahepatic diseases.

Joining Two Switches in One Nano-Object: Photoacidity and Photoisomerization in Electrostatic Self-Assembly

Multi-switchable supramolecular nano-objects that respond to irradiation of different wavelengths with changes in size and shape have been built from two different water-soluble molecular switches, joined by attachment to the same polyelectrolyte. Accordingly, two wavelength-specific reactions, namely the excited-state proton dissociation of a photoacid and the cis-trans isomerization of an azo dye, are combined in one supramolecular nano-object that is stable in aqueous solution. The concept has potential in the fields of sensors, molecular motors, and transport.

Photocleavable Anionic Glues for Light-Responsive Nanoparticle Aggregates

Integrating light-sensitive molecules within nanoparticle (NP) assemblies is an attractive approach to fabricate new photoresponsive nanomaterials. Here, we describe the concept of photocleavable anionic glue (PAG): small trianions capable of mediating interactions between (and inducing the aggregation of) cationic NPs by means of electrostatic interactions. Exposure to light converts PAGs into dianionic products incapable of maintaining the NPs in an assembled state, resulting in light-triggered disassembly of NP aggregates. To demonstrate the proof-of-concept, we work with an organic PAG incorporating the UV-cleavable o-nitrobenzyl moiety and an inorganic PAG, the photosensitive trioxalatocobaltate(III) complex, which absorbs light across the entire visible spectrum. Both PAGs were used to prepare either amorphous NP assemblies or regular superlattices with a long-range NP order. These NP aggregates disassembled rapidly upon light exposure for a specific time, which could be tuned by the incident light wavelength or the amount of PAG used. Selective excitation of the inorganic PAG in a system combining the two PAGs results in a photodecomposition product that deactivates the organic PAG, enabling nontrivial disassembly profiles under a single type of external stimulus.

Precise Controlled Target Molecule Release through Light-Triggered Charge Reversal Bridged Polysilsesquioxane Nanoparticles

Precise control of target molecule release time, site, and dosage remains a challenge in controlled release systems. We employed a photoresponsive molecule release system via light-triggered charge reversal nanoparticles to achieve a triggered, stepwise, and precise controlled release platform. This release system was based on photocleavage-bridged polysilsesquioxane nanoparticles which acted as nanocarriers of doxorubicin loaded on the surface via electrostatic interaction. The nanoparticles could reverse into positive charges triggered by 254 nm light irradiation due to the photocleavage of the o-nitrobenzyl bridged segment. The charge reversal property of the nanoparticles could release loaded molecules. Doxorubicin was selected as a positively charged model molecule. The as-prepared nanoparticles with an average size of 124 nm had an acceptable doxorubicin loading content up to 12.8%. The surface charge of the nanoparticles could rapidly reverse from negative (−28.20 mV) to positive (+18.9 mV) upon light irradiation for only 10 min. In vitro release experiments showed a cumulative release up to 96% with continuously enhancing irradiation intensity. By regulating irradiation parameters, precisely controlled drug release was carried out. The typical “stepped” profile could be accurately controlled in an on/off irradiation mode. This approach provides an ideal light-triggered molecule release system for location, timing, and dosage. This updated controlled release system, triggered by near-infrared or infrared light, will have greater potential applications in biomedical technology.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

On-demand and tunable dual wavelength release of antibody using light-responsive hydrogels

There has been an increased interest in the use of protein therapeutics, especially antibodies, for the treatment of a variety of diseases due to their high specificity to tissues and biological pathways of interest. However, the use of antibodies can be hindered by physical aggregation, degradation, and diffusion when injected in vivo leading to the need for antibody-releasing depots for the controlled and localized delivery within tissues of interest. Here, we investigated photolabile hydrogel chemistries for creating on-demand and tunable antibody release profiles. Innovative, scalable synthetic procedures were established and applied for fabricating hydrogels with nitrobenzyl (NB) and coumarin (CMR) photolabile crosslinks that responded to clinically relevant doses of long-wavelength UV and short-wavelength visible light. This synthetic procedure includes a route to make a CMR linker possessing two functional handles at the same ring position with water-stable bonds. The photocleavage properties of NB and CMR crosslinked hydrogels were characterized, as well as their potential for translational studies by degradation through pig skin, a good human skin mimic. The mechanism of hydrogel degradation, bulk versus surface eroding, was determined to be dependent on the wavelength of light utilized and the molar absorptivity of the different photolabile linkers, providing a facile means for altering protein release upon hydrogel degradation. Further, the encapsulation and on-demand release of a model monoclonal antibody was demonstrated, highlighting the ability to control antibody release from these hydrogels through the application of light while retaining its bioactivity. In particular, the newly designed CMR hydrogels undergo surface erosion-based protein release using visible light, which is more commonly used clinically. Overall, this work establishes scalable syntheses and relevant pairings of formulation-irradiation conditions for designing on-demand and light-responsive material systems that provide controlled, tunable release of bioactive proteins toward addressing barriers to preclinical translation of light-based materials and ultimately improving therapeutic regimens.

Controlling gene expression with light: a multidisciplinary endeavour

The expression of a gene to a protein is one of the most vital biological processes. The use of light to control biology offers unparalleled spatiotemporal resolution from an external, orthogonal signal. A variety of methods have been developed that use light to control the steps of transcription and translation of specific genes into proteins, for cell-free to in vivo biotechnology applications. These methods employ techniques ranging from the modification of small molecules, nucleic acids and proteins with photocages, to the engineering of proteins involved in gene expression using naturally light-sensitive proteins. Although the majority of currently available technologies employ ultraviolet light, there has been a recent increase in the use of functionalities that work at longer wavelengths of light, to minimise cellular damage and increase tissue penetration. Here, we discuss the different chemical and biological methods employed to control gene expression, while also highlighting the central themes and the most exciting applications within this diverse field.

Photosensitive Poly-l-lysine/Heparin Interpolyelectrolyte Complexes for Delivery of Genetic Drugs

Photo-triggered release of biopharmaceutical drugs inside the cells is a challenging direction of modern science, which requires obtaining new polymeric systems. The interpolyelectrolyte complexes (IPECs) of poly-l-lysine with heparin capable of encapsulation of genetic constructions—such as model oligonucleotide, siRNA, and pDNA—were obtained. Poly-l-lysine to heparin ratios were optimized to provide the appropriate release kinetics of genetic material from the polyplex. In order to impart the obtained IPEC with photosensitive properties, the linker was synthesized as based on 4-brommethyl-3-nitrobenzoic acid. The conditions and kinetics of photosensitive linker destruction were carefully studied. The colloid particles of IPEC were modified with Cy3 probe and their cellular internalization was investigated by flow cytometry method. The efficacy of photosensitive IPECs as siRNA and pDNA delivery system was evaluated.

Highly efficient gene release in spatiotemporal precision approached by light and pH dual responsive copolymers

Triblock copolymer of poly(ethylene glycol)-b-poly(2-dimethylaminoethyl methacrylate)-b-poly(pyrenylmethyl methacrylate) (PEG-b-PDMAEMA-b-PPy) has been developed for use as an ideal gene delivery system, which showed both high stability under physiological conditions and efficient gene release in a mimetic cancer environment. The siRNA release from this system without external stimulation was 16% in 1 h and then remained steady. However, the photo-triggered siRNA release was 78% within 1 h and was higher than 91% after 24 h. The remarkable contrast between the stability and release efficiency of these siRNA-condensed micelleplexes before and after photo-irradiation has been rationalized by the light- and pH-induced structural transitions of the triblock copolymer micelles. The negligible cytotoxicity, high cellular uptake efficiency, and remarkable knockdown efficiency shown in in vitro tests further revealed the promising potential of these triblock copolymer micelleplexes for use in stimuli-responsive gene therapy.

Photo-responsive hollow silica nanoparticles for light-triggered genetic and photodynamic synergistic therapy

The development of multifunctional carriers incorporating genetic and photodynamic therapy (PDT) for synergistic antitumor treatment has attracted intensive interests very recently. However, most of the currently reported systems employ passive gene release strategies depending on tumor microenvironment, which are negatively affected by the heterogeneity of cancer cells, thus resulting in limited controllability in therapeutic progress. Herein, a novel photo-responsive hollow silica nanoparticle (HNP)-based gene and photosensitizer (PS) co-delivery nanovehicle is designed for dual-wavelength light-triggered synergistic gene and PDT therapy. The resultant HNP conjugated with PDMAEMA polycation through a 405-nm light-cleavable Cou-linker, namely, HNP-Cou-PD, exhibits excellent gene condensation capacity, good biocompatibility, outstanding PS loading ability, and light-triggered gene release properties. HNP-Cou-PD with Chlorin e6 (Ce6) loaded inside the silica cavity and a plasmid encoding caspase-8 gene (CSP8) attached to the PDMAEMA outside layer (Ce6-HNP-Cou-PD/CSP8) has been proven to possess better antitumor effects under the irradiation of pre-405-nm and post-670-nm light both in vitro and in vivo because of the light-triggered intracellular gene release and reactive oxygen species (ROS) generation. Therefore, HNP-Cou-PD designed as a gene and PS co-delivery carrier might have promising applications in the future to precisely treat various types of cancers.

STATEMENT OF SIGNIFICANCE

Multifunctional carriers incorporating genetic and photodynamic therapy (PDT) have drawn intense attention very recently, ascribing to their enhanced anticancer effects. However, in the present gene and PDT synergistic system, gene release strategies passively relying on tumor microenvironment often result in no or poor controllability compared with PDT (a spatial and temporal therapeutic modal), which may hinder their synergistic efficacy, especially in an on-demand manner. To resolve this problem, we designed a hollow silica nanoparticle-based dual-wavelength light-responsive gene and photosensitizer (PS) co-delivery platform to achieve photo-triggered gene and PDT synergistic therapy. We believe that our work may have extensive application prospects in precise treatment of various cancers and be of interest to the readership.

Hydroxyethyl substituted linear polyethylenimine for safe and efficient delivery of siRNA therapeutics

Linear polyethylenimine (LPEI) has been well reported as a carrier for siRNA delivery. However, its applications are limited due to its highly ionized state at physiologic pH and the resultant charge mediated toxicity. The presence of ionizable secondary amines in LPE are responsible for its unique characteristics such as pH dependent solubility and positive charge. Therefore, modification of LPEI was carried out to obtain hydroxyethyl substituted LPEI with the degree of substitution ranging from 15% to 45%. The impact of modification on the physicochemical parameters of the polymer, i.e. buffer capacity, solubility, biocompatibility and stability, was evaluated. Surprisingly, despite the loss of ionizable amines, the substitution improved solubility, and even overcame the pH dependent solubility of LPEI. In addition, the conversion of secondary amines to less basic tertiary amines after substitution improved the buffer capacity, in the endosomal pH range, required for efficient endosomal escape. It also reduced erythrocyte aggregation, hemolytic potential and in vitro cytotoxicity. The in vitro studies showed enhanced cell uptake and mRNA knockdown efficiency. Thus, the proposed modification shows a simple approach to overcome the limitation of LPEI for siRNA delivery.

Hydroxyethyl substitution of linear polyethylenimine (LPEI) and its effects on physico-chemical and biological properties of polymer.

Intracellular delivery of more than one protein with spatio-temporal control

Transient, non-integrative modulation of cell function by intracellular delivery of proteins has high potential in cellular reprogramming, gene editing and therapeutic medicine applications. Unfortunately, the capacity to deliver multiple proteins intracellularly with temporal and spatial control has not been demonstrated. Here, we report a near infrared (NIR) laser-activatable nanomaterial that allows for precise control over the release of two proteins from a single nanomaterial. The nanomaterial is formed by gold nanorods (AuNRs) modified with single stranded DNA (ssDNA) to which complementary DNA-conjugated proteins are hybridized. Using DNA strands with distinct melting temperatures we are able to control independently the release of each protein with a laser using the same wavelength but with different powers. Studies in mammalian cells show that AuNRs conjugated with proteins are internalized by endocytosis and NIR laser irradiation promotes endosomal escape and the release of the proteins from the AuNRs simultaneously. Our results further demonstrate the feasibility of protein release from a carrier that has been accumulated within the cell up to 1 day while maintaining its activity.

Attenuation of Maladaptive Responses in Aortic Adventitial Fibroblasts through Stimuli-Triggered siRNA Release from Lipid-Polymer Nanocomplexes

Lipid-siRNA assemblies are modified with photo-responsive polymers to enable spatiotemporally-controlled silencing of interleukin 1 beta (IL1β) and cadherin 11 (CDH11), two genes that are essential drivers of maladaptive responses in human aortic adventitial fibroblasts (AoAFs). These hybrid nanocomplexes address the critical challenge of locally mitigating fibrotic actions that lead to the high rates of vascular graft failures. In particular, the lipid-polymer formulations provide potent silencing of IL1β and CDH11 that is precisely modulated by a photo-release stimulus. Moreover, a dynamic modeling framework is used to design a multi-dose siRNA regimen that sustains knockdown of both genes over clinically-relevant timescales. Multi-dose suppression illuminates a cooperative role for IL1β and CDH11 in pathogenic adventitial remodeling and is directly linked to desirable functional outcomes. Specifically, myofibroblast differentiation and cellular proliferation, two of the primary hallmarks of fibrosis, are significantly attenuated by IL1β silencing. Meanwhile, the effects of CDH11 siRNA treatment on differentiation become more pronounced at higher cell densities characteristic of constrictive adventitial remodeling in vivo. Thus, this work offers a unique formulation design for photo-responsive gene suppression in human primary cells and establishes a new dosing method to satisfy the critical need for local attenuation of fibrotic responses in the adventitium surrounding vascular grafts.

Predicting Gene Silencing Through the Spatiotemporal Control of siRNA Release from Photo-responsive Polymeric Nanocarriers

New materials and methods are needed to better control the binding vs. release of nucleic acids for a wide range of applications that require the precise regulation of gene activity. In particular, novel stimuli-responsive materials with improved spatiotemporal control over gene expression would unlock translatable platforms in drug discovery and regenerative medicine technologies. Furthermore, an enhanced ability to control nucleic acid release from materials would enable the development of streamlined methods to predict nanocarrier efficacy a priori, leading to expedited screening of delivery vehicles. Herein, we present a protocol for predicting gene silencing efficiencies and achieving spatiotemporal control over gene expression through a modular photo-responsive nanocarrier system. Small interfering RNA (siRNA) is complexed with mPEG-b-poly(5-(3-(amino)propoxy)-2-nitrobenzyl methacrylate) (mPEG-b-P(APNBMA)) polymers to form stable nanocarriers that can be controlled with light to facilitate tunable, on/off siRNA release. We outline two complementary assays employing fluorescence correlation spectroscopy and gel electrophoresis for the accurate quantification of siRNA release from solutions mimicking intracellular environments. Information gained from these assays was incorporated into a simple RNA interference (RNAi) kinetic model to predict the dynamic silencing responses to various photo-stimulus conditions. In turn, these optimized irradiation conditions allowed refinement of a new protocol for spatiotemporally controlling gene silencing. This method can generate cellular patterns in gene expression with cell-to-cell resolution and no detectable off-target effects. Taken together, our approach offers an easy-to-use method for predicting dynamic changes in gene expression and precisely controlling siRNA activity in space and time. This set of assays can be readily adapted to test a wide variety of other stimuli-responsive systems in order to address key challenges pertinent to a multitude of applications in biomedical research and medicine.

Anionic Polymer and Quantum Dot Excipients to Facilitate siRNA Release and Self-Reporting of Disassembly in Stimuli-Responsive Nanocarrier Formulations

The incorporation of anionic excipients into polyplexes is a promising strategy for modulating siRNA binding versus release and integrating diagnostic capabilities; however, specific design criteria and structure-function relationships are needed to facilitate the development of nanocarrier-based theranostics. Herein, we incorporated poly(acrylic acid) (PAA) and quantum dot (QD) excipients into photolabile siRNA polyplexes to increase gene silencing efficiencies by up to 100% and enable self-reporting of nanocarrier disassembly. Our systematic approach identified the functional relationships between gene silencing and key parameters such as excipient loading fractions and molecular weights that facilitated the establishment of design rules for optimization of nanocarrier efficacy. For example, we found that PAA molecular weights ∼10-20× greater than that of the coencapsulated siRNA exhibited the most efficient release and silencing. Furthermore, siRNA release assays and RNAi modeling allowed us to generate a PAA "heat map" that predicted gene silencing a priori as a function of PAA molecular weight and loading fraction. QDs further promoted selective siRNA release and provided visual as well as Förster resonance energy transfer (FRET)-based monitoring of the dynamic changes in nanostructure in situ. Moreover, even with the addition of anionic components, our formulations exhibited substantially improved stability and shelf life relative to typical formulations, with complete stability after a week of storage and full activity in the presence of serum. Taken together, this study enabled synergistic improvements in siRNA release and diagnostic capabilities, along with the development of mechanistic insights that are critical for advancing the translation of nucleic acid theranostics into the clinic.

Highly Efficient and Safe Delivery of VEGF siRNA by Bioreducible Fluorinated Peptide Dendrimers for Cancer Therapy

RNA interference (RNAi) has a great promise in treating various acquired and hereditary diseases. However, it remains highly desirable to develop new delivery system to circumvent complex extra- and intracellular barriers for successful clinical translation. Here, we report on a versatile polymeric vector, bioreducible fluorinated peptide dendrimers (BFPD), for efficient and safe small interfering RNA (siRNA) delivery. In virtue of skillfully integrating all of the unique advantages of reversible cross-linking, fluorination, and peptide dendrimers, this novel vector can surmount almost all extra- and intracellular barriers associated with local siRNA delivery through highly improved physiological stability and serum resistance, significantly increased intratumoral enrichment, cellular internalization, successful facilitation of endosomal escape, and cytosolic siRNA release. BFPD polyplexes, carrying small interfering vascular endothelial growth factor (siVEGF), demonstrated excellent VEGF silencing efficacy (∼65%) and a strong capability for inhibiting HeLa cell proliferation. More importantly, these polyplexes showed superior performance in long-term enrichment in the tumor sites and had a high level of tumor growth inhibition. Furthermore, these polyplexes not only exhibited excellent in vivo antitumor efficacy but also demonstrated superior biocompatibility, compared with LPF2000, both in vivo and in vitro. These findings indicate that BFPD is an efficient and safe siRNA delivery system and has remarkable potential for RNAi-based cancer treatment.

Efficient tuning of siRNA dose response by combining mixed polymer nanocarriers with simple kinetic modeling

Two of the most prominent challenges that limit the clinical success of siRNA therapies are a lack of control over cargo release from the delivery vehicle and an incomplete understanding of the link between gene silencing dynamics and siRNA dosing. Herein, we address these challenges through the formulation of siRNA polyplexes containing light-responsive polymer mixtures, whose varied compositions and triggered release behavior provide enhanced gene silencing and controlled dose responses that can be predicted by simple kinetic models. Through the straightforward mixing of two block copolymers, the level of gene knockdown was easily optimized to achieve the maximum level of GAPDH protein silencing in NIH/3T3 cells (~70%) using a single siRNA dose. The kinetic model was used to describe the dynamic changes in mRNA and protein concentrations in response to siRNA treatment. These predictions enabled the application of a second dose of siRNA to maximally suppress gene expression over multiple days, leading to a further 50% reduction in protein levels relative to those measured following a single dose. Furthermore, polyplexes remained dormant in cells until exposed to the photo-stimulus, demonstrating the complete control over siRNA activity as well as the stability of the nanocarriers. Thus, this work demonstrates that pairing advances in biomaterials design with simple kinetic modeling provides new insight into gene silencing dynamics and presents a powerful strategy to control gene expression through siRNA delivery.

STATEMENT OF SIGNIFICANCE

Our manuscript describes two noteworthy impacts: (1) we designed mixed polymer formulations to enhance gene silencing, and (2) we simultaneously developed a simple kinetic model for determining optimal siRNA dose responses to maintain silencing over several days. These advances address critical challenges in siRNA delivery and provide new opportunities in therapeutics development. The structure-function relationships prevalent in these formulations were established to enable tuning and forecasting of nanocarrier efficiency a priori, leading to siRNA dosing regimens able to maximally suppress gene expression. Our advances are significant because the mixed polymer formulations provide a straightforward and scalable approach to tailor siRNA delivery regimens. Moreover, the implementation of accurate dosing frameworks addresses a major knowledge gap that has hindered clinical implementation of siRNA.

Polymeric Biomaterials: Diverse Functions Enabled by Advances in Macromolecular Chemistry

Biomaterials have been extensively used to leverage beneficial outcomes in various therapeutic applications, such as providing spatial and temporal control over the release of therapeutic agents in drug delivery as well as engineering functional tissues and promoting the healing process in tissue engineering and regenerative medicine. This perspective presents important milestones in the development of polymeric biomaterials with defined structures and properties. Contemporary studies of biomaterial design have been reviewed with focus on constructing materials with controlled structure, dynamic functionality, and biological complexity. Examples of these polymeric biomaterials enabled by advanced synthetic methodologies, dynamic chemistry/assembly strategies, and modulated cell-material interactions have been highlighted. As the field of polymeric biomaterials continues to evolve with increased sophistication, current challenges and future directions for the design and translation of these materials are also summarized.

Light-triggered RNA release and induction of hMSC osteogenesis via photodegradable, dual-crosslinked hydrogels

AIM

To engineer a photodegradable hydrogel system for actively controlled release of bioactive unmodified RNA at designated time points to induce hMSC osteogenesis.

MATERIALS & METHODS

RNA/polyethylenimine complexes were loaded into dual-crosslinked photodegradable hydrogels to examine the capacity of UV light application to trigger their release. The ability of released RNA to drive hMSC osteogenic differentiation was also investigated.

RESULTS & CONCLUSION

RNA release from photodegradable hydrogels was accelerated upon UV application, which was not observed in non-photodegradable hydrogels. Regardless of the presence of UV light, released siGFP exhibited high bioactivity by silencing GFP expression in HeLa cells. Importantly, siNoggin or miRNA-20a released from the hydrogels induced hMSC osteogenesis. This system provides a potentially valuable physician/patient-controlled 'on-demand' RNA delivery platform for biomedical applications.

Hydrophobic interactions between polymeric carrier and palmitic acid-conjugated siRNA improve PEGylated polyplex stability and enhance in vivo pharmacokinetics and tumor gene silencing

Formation of stable, long-circulating siRNA polyplexes is a significant challenge in translation of intravenously-delivered, polymeric RNAi cancer therapies. Here, we report that siRNA hydrophobization through conjugation to palmitic acid (siPA) improves stability, in vivo pharmacokinetics, and tumor gene silencing of PEGylated nanopolyplexes (siPA-NPs) with balanced cationic and hydrophobic content in the core relative to the analogous polyplexes formed with unmodified siRNA, si-NPs. Hydrophobized siPA loaded into the NPs at a lower charge ratio (N(+):P(-)) relative to unmodified siRNA, and siPA-NPs had superior resistance to siRNA cargo unpackaging in comparison to si-NPs upon exposure to the competing polyanion heparin and serum. In vitro, siPA-NPs increased uptake in MDA-MB-231 breast cancer cells (100% positive cells vs. 60% positive cells) but exhibited equivalent silencing of the model gene luciferase relative to si-NPs. In vivo in a murine model, the circulation half-life of intravenously-injected siPA-NPs was double that of si-NPs, resulting in a >2-fold increase in siRNA biodistribution to orthotopic MDA-MB-231 mammary tumors. The increased circulation half-life of siPA-NPs was dependent upon the hydrophobic interactions of the siRNA and the NP core component and not just siRNA hydrophobization, as siPA did not contribute to improved circulation time relative to unmodified siRNA when delivered using polyplexes with a fully cationic core. Intravenous delivery of siPA-NPs also achieved significant silencing of the model gene luciferase in vivo (∼40% at 24 h after one treatment and ∼60% at 48 h after two treatments) in the murine MDA-MB-231 tumor model, while si-NPs only produced a significant silencing effect after two treatments. These data suggest that stabilization of PEGylated siRNA polyplexes through a combination of hydrophobic and electrostatic interactions between siRNA cargo and the polymeric carrier improves in vivo pharmacokinetics and tumor gene silencing relative to conventional formulations that are stabilized solely by electrostatic interactions.

Photocleavable Hydrogels for Light-Triggered siRNA Release

A photocleavable hydrogel system for on-demand delivery of genetic material is reported. The release of short interfering RNAs can be triggered by the application of UV light without any loss in bioactivity. This approach provides a promising external stimulus-based nucleic acid delivery platform for applications in disease therapeutics and tissue regeneration.

Hydrolytic charge-reversal of PEGylated polyplexes enhances intracellular un-packaging and activity of siRNA

Hydrolytically degrading nano-polyplexes (HDG-NPs) that reverse charge through conversion of tertiary amines to carboxylic acids were investigated to improve intracellular un-packaging of siRNA and target gene silencing compared to a non-degradable analog (non-HDG-NPs). Both NP types comprised reversible addition-fragmentation chain-transfer (RAFT) synthesized diblock copolymers of a poly(ethylene glycol) (PEG) corona-forming block and a cationic block for nucleic acid packaging that incorporated butyl methacrylate (BMA) and either dimethylaminoethyl methacrylate (DMAEMA, non-HDG-NPs) or dimethylaminoethyl acrylate (DMAEA, HDG-NPs). HDG-NPs decreased significantly in size and released significantly more siRNA (∼40%) than non-HDG-NPs after 24 h in aqueous solution. While both HDG-NPs and non-HDG-NPs had comparable uptake and cytotoxicity up to 150 nM siRNA doses, HDG-NPs achieved significantly higher target gene silencing of the model gene luciferase in vitro. High resolution FRET confocal microscopy was used to monitor the intracellular un-packaging of siRNA. Non-HDG-NPs had significantly higher FRET efficiency than HDG-NPs, indicating that siRNA delivered from HDG-NPs was more fully un-packaged and therefore had improved intracellular bioavailability.

Low molecular weight chitosan–protamine conjugate for siRNA delivery with enhanced stability and transfection efficiency

Chitosan is among the few polymers with high biocompatibility and low cytotoxicity.

Enhancing potency of siRNA targeting fusion genes by optimization outside of target sequence

Canonical siRNA design algorithms have become remarkably effective at predicting favorable binding regions within a target mRNA, but in some cases (e.g., a fusion junction site) region choice is restricted. In these instances, alternative approaches are necessary to obtain a highly potent silencing molecule. Here we focus on strategies for rational optimization of two siRNAs that target the junction sites of fusion oncogenes BCR-ABL and TMPRSS2-ERG. We demonstrate that modifying the termini of these siRNAs with a terminal G-U wobble pair or a carefully selected pair of terminal asymmetry-enhancing mismatches can result in an increase in potency at low doses. Importantly, we observed that improvements in silencing at the mRNA level do not necessarily translate to reductions in protein level and/or cell death. Decline in protein level is also heavily influenced by targeted protein half-life, and delivery vehicle toxicity can confound measures of cell death due to silencing. Therefore, for BCR-ABL, which has a long protein half-life that is difficult to overcome using siRNA, we also developed a nontoxic transfection vector: poly(lactic-coglycolic acid) nanoparticles that release siRNA over many days. We show that this system can achieve effective killing of leukemic cells. These findings provide insights into the implications of siRNA sequence for potency and suggest strategies for the design of more effective therapeutic siRNA molecules. Furthermore, this work points to the importance of integrating studies of siRNA design and delivery, while heeding and addressing potential limitations such as restricted targetable mRNA regions, long protein half-lives, and nonspecific toxicities.

Peptide-like Polymers Exerting Effective Glioma-Targeted siRNA Delivery and Release for Therapeutic Application

Lipopolymer 49, a solid-phase synthesized T-shaped peptide-like oligoamide containing two central oleic acids, 20 aminoethane, and two terminal cysteine units, is identified as very potent and biocompatible small interfering RNA (siRNA) carrier for gene silencing in glioma cells. This carrier is combined with a novel targeting polymer 727, containing a precise sequence of Angiopep 2 targeting peptide, linked with 28 monomer units of ethylene glycol, 40 aminoethane, and two terminal cysteines in siRNA complex formation. Angiopep-polyethylene glycol (PEG)/siRNA polyplexes exhibit good nanoparticle features, effective glioma-targeting siRNA delivery, and intracellular siRNA release, resulting in an outstanding gene downregulation both in glioma cells and upon intravenous delivery in glioma model nude mice without significant biotoxicity. Therefore, this novel siRNA delivery system is expected to be a promising strategy for targeted and safe glioma therapy.