Hyaluronic acid and fibrin hydrogels with concentrated DNA/PEI polyplexes for local gene delivery

Advancements in Omics and Breakthrough Gene Therapies: A Glimpse into the Future of Peripheral Artery Disease

Peripheral artery disease (PAD), a highly prevalent global disease, associates with significant morbidity and mortality in affected patients. Despite progress in endovascular and open revascularization techniques for advanced PAD, these interventions grapple with elevated rates of arterial restenosis and vein graft failure attributed to intimal hyperplasia (IH). Novel multiomics technologies, coupled with sophisticated analyses tools recently powered by advances in artificial intelligence, have enabled the study of atherosclerosis and IH with unprecedented single-cell and spatial precision. Numerous studies have pinpointed gene hubs regulating pivotal atherogenic and atheroprotective signaling pathways as potential therapeutic candidates. Leveraging advancements in viral and nonviral gene therapy (GT) platforms, gene editing technologies, and cutting-edge biomaterial reservoirs for delivery uniquely positions us to develop safe, efficient, and targeted GTs for PAD-related diseases. Gene therapies appear particularly fitting for ex vivo genetic engineering of IH-resistant vein grafts. This manuscript highlights currently available state-of-the-art multiomics approaches, explores promising GT-based candidates, and details GT delivery modalities employed by our laboratory and others to thwart mid-term vein graft failure caused by IH, as well as other PAD-related conditions. The potential clinical translation of these targeted GTs holds the promise to revolutionize PAD treatment, thereby enhancing patients' quality of life and life expectancy.

Hydrogels for Nucleic Acid Drugs Delivery

Nucleic acid drugs are one of the hot spots in the field of biomedicine in recent years, and play a crucial role in the treatment of many diseases. However, its low stability and difficulty in target drug delivery are the bottlenecks restricting its application. Hydrogels are proven to be promising for improving the stability of nucleic acid drugs, reducing the adverse effects of rapid degradation, sudden release, and unnecessary diffusion of nucleic acid drugs. In this review, the strategies of loading nucleic acid drugs in hydrogels are summarized for various biomedical research, and classify the mechanism principles of these strategies, including electrostatic binding, hydrogen bond based binding, hydrophobic binding, covalent bond based binding and indirect binding using various carriers. In addition, this review also describes the release strategies of nucleic acid drugs, including photostimulation-based release, enzyme-responsive release, pH-responsive release, and temperature-responsive release. Finally, the applications and future research directions of hydrogels for delivering nucleic acid drugs in the field of medicine are discussed.

Transforming Cell-Drug Interaction through Granular Hydrogel-Mediated Delivery of Polyplex Nanoparticles for Enhanced Safety and Extended Efficacy in Gene Therapy

The utilization of hydrogels for DNA/cationic polymer polyplex nanoparticle (polyplex) delivery has significantly advanced gene therapy in tissue regeneration and cancer treatment. However, persistent challenges related to the efficacy and safety of encapsulated polyplexes, stemming from issues such as aggregation, degradation, or difficulties in controlled release during or postintegration with hydrogel scaffolds, necessitate further exploration. Here, we introduce an injectable gene therapy gel achieved by incorporating concentrated polyplexes onto densely packed hydrogel microparticles (HMPs). Polyplexes, when uniformly adhered to the gene therapy gel through reversible electrostatic interactions, can detach from the HMP surface in a controlled manner, contrasting with free polyplexes, and thereby reducing dose-dependent toxicity during transfection. Additionally, the integration of RGD cell adhesion peptides enhances the scaffolding characteristics of the gel, facilitating cell adhesion, migration, and further minimizing toxicity during gene drug administration. Notably, despite the overall transfection efficiency showing average performance, utilizing confocal microscopy to meticulously observe and analyze the cellular states infiltrating into various depths of the gene therapy gel resulted in the groundbreaking discovery of significantly enhanced local transfection efficiency, with primary cell transfection approaching 80%. This phenomenon could be potentially attributed to the granular hydrogel-mediated delivery of polyplex nanoparticles, which revolutionizes the spatial and temporal distribution and thus the "encounter" mode between polyplexes and cells. Moreover, the gene therapy gel's intrinsic injectability and self-healing properties offer ease of administration, making it a highly promising candidate as a novel gene transfection gel dressing with significant potential across various fields, including regenerative medicine and innovative living materials.

Development of pro-angiogenic skin substitutes for wound healing

Wounds pose significant challenges to public health, primarily due to the loss of the mechanical integrity and barrier function of the skin and impaired angiogenesis, causing physical morbidities and psychological trauma to affect patients. Reconstructing the vasculature of the wound bed is crucial for promoting wound healing, reducing scar formation and enhancing the quality of life for patients. The development of pro-angiogenic skin substitutes has emerged as a promising strategy to facilitate vascularization and expedite the healing process of burn wounds. This review provides an overview of the various types of skin substitutes employed in wound healing, explicitly emphasising those designed to enhance angiogenesis. Synthetic scaffolds, biological matrices and tissue-engineered constructs incorporating stem cells and primary cells, cell-derived extracellular vesicles (EVs), pro-angiogenic growth factors and peptides, as well as gene therapy-based skin substitutes are thoroughly examined. The review summarises the existing challenges, future directions and potential innovations in pro-angiogenic dressing for skin substitutes. It highlights the need for continued research to develop new technologies and combine multiple strategies and factors, and to overcome obstacles and advance the field, ultimately leading to improved outcomes for wound patients.

Insights into Translational and Biomedical Applications of Hydrogels as Versatile Drug Delivery Systems

Hydrogels are a network of crosslinked polymers which can hold a huge amount of water in their matrix. These might be soft, flexible, and porous resembling living tissues. The incorporation of different biocompatible materials and nanostructures into the hydrogels has led to emergence of multifunctional hydrogels with advanced properties. There are broad applications of hydrogels such as tissue culture, drug delivery, tissue engineering, implantation, water purification, and dressings. Besides these, it can be utilized in the field of medical surgery, in biosensors, targeted drug delivery, and drug release. Similarly, hyaluronic acid hydrogels have vast applications in biomedicines such as cell delivery, drug delivery, molecule delivery, micropatterning in cellular biology for tissue engineering, diagnosis and screening of diseases, tissue repair and stem cell microencapsulation in case of inflammation, angiogenesis, and other biological developmental processes. The properties like swellability, de-swellability, biodegradability, biocompatibility, and inert nature of the hydrogels in contact with body fluids, blood, and tissues make its tremendous application in the field of modern biomedicines nowadays. Various modifications in hydrogel formulations have widened their therapeutic applicability. These include 3D printing, conjugation, thiolation, multiple anchoring, and reduction. Various hydrogel formulations are also capable of dual drug delivery, dental surgery, medicinal implants, bone diseases, and gene and stem cells delivery. The presented review summarizes the unique properties of hydrogels along with their methods of preparation and significant biomedical applications as well as different types of commercial products available in the market and the regulatory guidance.

Tissue-Engineered Nanomaterials Play Diverse Roles in Bone Injury Repair

Nanomaterials with bone-mimicking characteristics and easily internalized by the cell could create suitable microenvironments in which to regulate the therapeutic effects of bone regeneration. This review provides an overview of the current state-of-the-art research in developing and using nanomaterials for better bone injury repair. First, an overview of the hierarchical architecture from the macroscale to the nanoscale of natural bone is presented, as these bone tissue microstructures and compositions are the basis for constructing bone substitutes. Next, urgent clinical issues associated with bone injury that require resolution and the potential of nanomaterials to overcome them are discussed. Finally, nanomaterials are classified as inorganic or organic based on their chemical properties. Their basic characteristics and the results of related bone engineering studies are described. This review describes theoretical and technical bases for the development of innovative methods for repairing damaged bone and should inspire therapeutic strategies with potential for clinical applications.

Matrices Activated with Messenger RNA

Over two decades of preclinical and clinical experience have confirmed that gene therapy-activated matrices are potent tools for sustained gene modulation at the implantation area. Matrices activated with messenger RNA (mRNA) are the latest development in the area, and they promise an ideal combination of efficiency and safety. Indeed, implanted mRNA-activated matrices allow a sustained delivery of mRNA and the continuous production of therapeutic proteins in situ. In addition, they are particularly interesting to generate proteins acting on intracellular targets, as the translated protein can directly exert its therapeutic function. Still, mRNA-activated matrices are incipient technologies with a limited number of published records, and much is still to be understood before their successful implementation. Indeed, the design parameters of mRNA-activated matrices are crucial for their performance, as they affect mRNA stability, device immunogenicity, translation efficiency, and the duration of the therapy. Critical design factors include matrix composition and its mesh size, mRNA chemical modification and sequence, and the characteristics of the nanocarriers used for mRNA delivery. This review aims to provide some background relevant to these technologies and to summarize both the design space for mRNA-activated matrices and the current knowledge regarding their pharmaceutical performance. Furthermore, we will discuss potential applications of mRNA-activated matrices, mainly focusing on tissue engineering and immunomodulation.

Tuning Peptide-Based Hydrogels: Co-Assembly with Composites Driving the Highway to Technological Applications

Self-assembled peptide-based gels provide several advantages for technological applications. Recently, the co-assembly of gelators has been a strategy to modulate and tune gel properties and even implement stimuli-responsiveness. However, it still comprises limitations regarding the required library of compounds and outcoming properties. Hence, efforts have been made to combine peptide-based gels and (in)organic composites (e.g., magnetic nanoparticles, metal nanoparticles, liposomes, graphene, silica, clay, titanium dioxide, cadmium sulfide) to endow stimuli-responsive materials and achieve suitable properties in several fields ranging from optoelectronics to biomedical. Herein, we discuss the recent developments with composite peptide-based gels including the fabrication, tunability of gels' properties, and challenges on (bio)technological applications.

In vivo restoration of dystrophin expression in mdx mice using intra-muscular and intra-arterial injections of hydrogel microsphere carriers of exon skipping antisense oligonucleotides

Duchenne muscular dystrophy (DMD) is a genetic disease caused by a mutation in the X-linked Dytrophin gene preventing the expression of the functional protein. Exon skipping therapy using antisense oligonucleotides (AONs) is a promising therapeutic strategy for DMD. While benefits of AON therapy have been demonstrated, some challenges remain before this strategy can be applied more comprehensively to DMD patients. These include instability of AONs due to low nuclease resistance and poor tissue uptake. Delivery systems have been examined to improve the availability and stability of oligonucleotide drugs, including polymeric carriers. Previously, we showed the potential of a hydrogel-based polymeric carrier in the form of injectable PEG-fibrinogen (PF) microspheres for delivery of chemically modified 2'-O-methyl phosphorothioate (2OMePs) AONs. The PF microspheres proved to be cytocompatible and provided sustained release of the AONs for several weeks, causing increased cellular uptake in mdx dystrophic mouse cells. Here, we further investigated this delivery strategy by examining in vivo efficacy of this approach. The 2OMePS/PEI polyplexes loaded in PF microspheres were delivered by intramuscular (IM) or intra-femoral (IF) injections. We examined the carrier biodegradation profiles, AON uptake efficiency, dystrophin restoration, and muscle histopathology. Both administration routes enhanced dystrophin restoration and improved the histopathology of the mdx mice muscles. The IF administration of the microspheres improved the efficacy of the 2OMePS AONs over the IM administration. This was demonstrated by a higher exon skipping percentage and a smaller percentage of centered nucleus fibers (CNF) found in H&E-stained muscles. The restoration of dystrophin expression found for both IM and IF treatments revealed a reduced dystrophic phenotype of the treated muscles. The study concludes that injectable PF microspheres can be used as a carrier system to improve the overall therapeutic outcomes of exon skipping-based therapy for treating DMD.

Investigating 3R In Vivo Approaches for Bio-Distribution and Efficacy Evaluation of Nucleic Acid Nanocarriers: Studies on Peptide-Mimicking Ionizable Lipid

Formulations based on ionizable amino-lipids have been put into focus as nucleic acid delivery systems. Recently, the in vitro efficacy of the lipid formulation OH4:DOPE has been explored. However, in vitro performance of nanomedicines cannot correctly predict in vivo efficacy, thereby considerably limiting pre-clinical translation. This is further exacerbated by limited access to mammalian models. The present work proposes to close this gap by investigating in vivo nucleic acid delivery within simpler models, but which still offers physiologically complex environments and also adheres to the 3R guidelines (replace/reduce/refine) to improve animal experiments. The efficacy of OH4:DOPE as a delivery system for nucleic acids is demonstrated using in vivo approaches. It is shown that the formulation is able to transfect complex tissues using the chicken chorioallantoic membrane model. The efficacy of DNA and mRNA lipoplexes is tested extensively in the zebra fish (Danio rerio) embryo which allows the screening of biodistribution and transfection efficiency. Effective transfection of blood vessel endothelial cells is seen, especially in the endocardium. Both model systems allow an efficacy screening according to the 3R guidelines bypassing the in vitro-in vivo gap. Pilot studies in mice are performed to correlate the efficacy of in vivo transfection.

Development of a fibrin-mediated gene delivery system for the treatment of cystinosis via design of experiment

Cystinosis is a rare disease, caused by a mutation in the gene cystinosin and characterised by the accumulation of cystine crystals. Advantages of biomaterial-mediated gene delivery include reduced safety concerns and the possibility to cure organs that are difficult to treat using systemic gene transfer methods. This study developed novel fibrin hydrogels for controlled, localised gene delivery, for the treatment of cystinosis. In the first part, fabrication parameters (i.e., DNA, thrombin, and aprotinin concentrations) were optimised, using a Design of Experiment (DOE) methodology. DOE is a statistical engineering approach to process optimisation, which increases experimental efficiency, reduces the number of experiments, takes into consideration interactions between different parameters, and allows the creation of predictive models. This study demonstrated the utility of DOE to the development of gene delivery constructs. In the second part of the study, primary fibroblasts from a patient with cystinosis were seeded on the biomaterials. Seeded cells expressed the recombinant CTNS and showed a decrease in cystine content. Furthermore, conditioned media contained functional copies of the recombinant CTNS. These were taken up by monolayer cultures of non-transfected cells. This study described a methodology to develop gene delivery constructs by using a DOE approach and ultimately provided new insights into the treatment of cystinosis.

Nucleic Acid Delivery from Granular Hydrogels

Nucleic acid delivery has applications ranging from tissue engineering to vaccine development to infectious disease. Cationic polymer condensed nucleic acids are used with surface-coated porous scaffolds and are able to promote long-term gene expression. However, due to surface loading of the scaffold, there is a limit to the amount of nucleic acid that can be loaded, resulting in decreasing expression rate over time. In addition, surface-coated scaffolds are generally non-injectable. Here, it is demonstrated that cationic polymer condensed nucleic acids can be effectively loaded into injectable granular hydrogel scaffolds by stabilizing the condensed nucleic acid into a lyophilized powder, loading the powder into a bulk hydrogel, and then fragmenting the loaded hydrogel. The resulting hydrogel microparticles contain non-aggregated nucleic acid particles, can be annealed post-injection to result in an injectable microporous hydrogel, and can effectively deliver nucleic acids to embedded cells with a constant expression rate. Due to the nature of granular hydrogels, it is demonstrated that mixtures of loaded and unloaded particles and spatially resolved gene expression can be easily achieved. The ability to express genes long term from an injectable porous hydrogel will further open the applications of nucleic acid delivery.

Smart/stimuli-responsive hydrogels: Cutting-edge platforms for tissue engineering and other biomedical applications

Recently, biomedicine and tissue regeneration have emerged as great advances that impacted the spectrum of healthcare. This left the door open for further improvement of their applications to revitalize the impaired tissues. Hence, restoring their functions. The implementation of therapeutic protocols that merge biomimetic scaffolds, bioactive molecules, and cells plays a pivotal role in this track. Smart/stimuli-responsive hydrogels are remarkable three-dimensional (3D) bioscaffolds intended for tissue engineering and other biomedical purposes. They can simulate the physicochemical, mechanical, and biological characters of the innate tissues. Also, they provide the aqueous conditions for cell growth, support 3D conformation, provide mechanical stability for the cells, and serve as potent delivery matrices for bioactive molecules. Many natural and artificial polymers were broadly utilized to design these intelligent platforms with novel advanced characteristics and tailored functionalities that fit such applications. In the present review, we highlighted the different types of smart/stimuli-responsive hydrogels with emphasis on their synthesis scheme. Besides, the mechanisms of their responsiveness to different stimuli were elaborated. Their potential for tissue engineering applications was discussed. Furthermore, their exploitation in other biomedical applications as targeted drug delivery, smart biosensors, actuators, 3D and 4D printing, and 3D cell culture were outlined. In addition, we threw light on smart self-healing hydrogels and their applications in biomedicine. Eventually, we presented their future perceptions in biomedical and tissue regeneration applications. Conclusively, current progress in the design of smart/stimuli-responsive hydrogels enhances their prospective to function as intelligent, and sophisticated systems in different biomedical applications.

Challenges and recent trends with the development of hydrogel fiber for biomedical applications

Hydrogel is the most emblematic soft material which possesses significantly tunable and programmable characteristics. Polymer hydrogels possess significant advantages including, biocompatible, simple, reliable and low cost. Therefore, research on the development of hydrogel for biomedical applications has been grown intensely. However, hydrogel development is challenging and required significant effort before the application at an industrial scale. Therefore, the current work focused on evaluating recent trends and issues with hydrogel development for biomedical applications. In addition, the hydrogel's development methodology, physicochemical properties, and biomedical applications are evaluated and benchmarked against the reported literature. Later, biomedical applications of the nano-cellulose-based hydrogel are considered and critically discussed. Based on a detailed review, it has been found that the surface energy, intermolecular interactions, and interactions of hydrogel adhesion forces are major challenges that contribute to the development of hydrogel. In addition, compared to other hydrogels, nanocellulose hydrogels demonstrated higher potential for drug delivery, 3D cell culture, diagnostics, tissue engineering, tissue therapies and gene therapies. Overall, nanocellulose hydrogel has the potential for commercialization for different biomedical applications.

The biological applications of DNA nanomaterials: current challenges and future directions

DNA, a genetic material, has been employed in different scientific directions for various biological applications as driven by DNA nanotechnology in the past decades, including tissue regeneration, disease prevention, inflammation inhibition, bioimaging, biosensing, diagnosis, antitumor drug delivery, and therapeutics. With the rapid progress in DNA nanotechnology, multitudinous DNA nanomaterials have been designed with different shape and size based on the classic Watson-Crick base-pairing for molecular self-assembly. Some DNA materials could functionally change cell biological behaviors, such as cell migration, cell proliferation, cell differentiation, autophagy, and anti-inflammatory effects. Some single-stranded DNAs (ssDNAs) or RNAs with secondary structures via self-pairing, named aptamer, possess the ability of targeting, which are selected by systematic evolution of ligands by exponential enrichment (SELEX) and applied for tumor targeted diagnosis and treatment. Some DNA nanomaterials with three-dimensional (3D) nanostructures and stable structures are investigated as drug carrier systems to delivery multiple antitumor medicine or gene therapeutic agents. While the functional DNA nanostructures have promoted the development of the DNA nanotechnology with innovative designs and preparation strategies, and also proved with great potential in the biological and medical use, there is still a long way to go for the eventual application of DNA materials in real life. Here in this review, we conducted a comprehensive survey of the structural development history of various DNA nanomaterials, introduced the principles of different DNA nanomaterials, summarized their biological applications in different fields, and discussed the current challenges and further directions that could help to achieve their applications in the future.

Spatially-directed angiogenesis using ultrasound-controlled release of basic fibroblast growth factor from acoustically-responsive scaffolds

Vascularization is a critical step following implantation of an engineered tissue construct in order to maintain its viability. The ability to spatially pattern or direct vascularization could be therapeutically beneficial for anastomosis and vessel in-growth. However, acellular and cell-based strategies to stimulate vascularization typically do not afford this control. We have developed an ultrasound-based method of spatially- controlling regenerative processes using acellular, composite hydrogels termed acoustically-responsive scaffolds (ARSs). An ARS consists of a fibrin matrix doped with a phase-shift double emulsion (PSDE). A therapeutic payload, which is initially contained within the PSDE, is released by an ultrasound-mediated process called acoustic droplet vaporization (ADV). During ADV, the perfluorocarbon (PFC) phase within the PSDE is vaporized into a gas bubble. In this study, we generated ex situ four different spatial patterns of ADV within ARSs containing basic fibroblast growth factor (bFGF), which were subcutaneously implanted in mice. The PFC species within the PSDE significantly affected the morphology of the ARS, based on the stability of the gas bubble generated by ADV, which impacted host cell migration. Irrespective of PFC, significantly greater cell proliferation (i.e., up to 2.9-fold) and angiogenesis (i.e., up to 3.7-fold) were observed adjacent to +ADV regions of the ARSs compared to -ADV regions. The morphology of the PSDE, macrophage infiltration, and perfusion in the implant region were also quantified. These results demonstrate that spatially-defined patterns of ADV within an ARS can elicit spatially-defined patterns of angiogenesis. Overall, these finding can be applied to improve strategies for spatially-controlling vascularization. STATEMENT OF SIGNIFICANCE: Vascularization is a critical step following implantation of an engineered tissue. The ability to spatially pattern or direct vascularization could be therapeutically beneficial for inosculation and vessel in-growth. However, acellular and cell-based strategies to stimulate vascularization typically do not afford this control. We have developed an ultrasound-based method of spatially-controlling angiogenesis using acellular, composite hydrogels termed acoustically-responsive scaffolds (ARSs). An ARS consists of a fibrin matrix doped with a phase-shift double emulsion (PSDE). An ultrasound-mediated process called acoustic droplet vaporization (ADV) was used to release basic fibroblast growth factor (bFGF), which was initially contained within the PSDE. We demonstrate that spatially-defined patterns of ADV within an ARS can elicit spatially-defined patterns of angiogenesis in vivo. Overall, these finding can improve strategies for spatially-controlling vascularization.

Nonviral Expression of LL-37 in a Human Skin Equivalent to Prevent Infection in Skin Wounds

Inefficient autologous tissue recovery in skin wounds increases the susceptibility of patients to infections caused by multidrug resistant microorganisms, resulting in a high mortality rate. Genetic modification of skin cells has become an important field of study because it could lead to the construction of more functional skin grafts, through the overexpression of antimicrobial peptides that would prevent early contamination and infection with bacteria. In this study, we produce and evaluate human skin equivalents (HSEs) containing transfected human primary fibroblasts and keratinocytes by polyplexes to express the antimicrobial peptide LL-37. The effect of LL-37 on the metabolic activity of normal HSEs was evaluated before the construction of the transfected HSEs, and the antimicrobial efficacy against Pseudomonas aeruginosa and Staphylococcus aureus was evaluated. Subsequently, the levels of LL-37 in the culture supernatants of transfected HSEs, as well as the local expression, were determined. It was found that LL-37 treatment significantly promoted the cellular proliferation of HSEs. Furthermore, HSEs that express elevated levels of LL-37 were shown to possess histological characteristics close to the normal skin and display enhanced antimicrobial activity against S. aureus in vitro. These findings demonstrate that HSEs expressing LL-37 through nonviral modification of skin cells are a promising approach for the prevention of bacterial colonization in wounds.

Physical and mechanical cues affecting biomaterial-mediated plasmid DNA delivery: insights into non-viral delivery systems

BACKGROUND

Whilst traditional strategies to increase transfection efficiency of non-viral systems aimed at modifying the vector or the polyplexes/lipoplexes, biomaterial-mediated gene delivery has recently sparked increased interest. This review aims at discussing biomaterial properties and unravelling underlying mechanisms of action, for biomaterial-mediated gene delivery. DNA internalisation and cytoplasmic transport are initially discussed. DNA immobilisation, encapsulation and surface-mediated gene delivery (SMD), the role of extracellular matrix (ECM) and topographical cues, biomaterial stiffness and mechanical stimulation are finally outlined.

MAIN TEXT

Endocytic pathways and mechanisms to escape the lysosomal network are highly variable. They depend on cell and DNA complex types but can be diverted using appropriate biomaterials. 3D scaffolds are generally fabricated via DNA immobilisation or encapsulation. Degradation rate and interaction with the vector affect temporal patterns of DNA release and transgene expression. In SMD, DNA is instead coated on 2D surfaces. SMD allows the incorporation of topographical cues, which, by inducing cytoskeletal re-arrangements, modulate DNA endocytosis. Incorporation of ECM mimetics allows cell type-specific transfection, whereas in spite of discordances in terms of optimal loading regimens, it is recognised that mechanical loading facilitates gene transfection. Finally, stiffer 2D substrates enhance DNA internalisation, whereas in 3D scaffolds, the role of stiffness is still dubious.

CONCLUSION

Although it is recognised that biomaterials allow the creation of tailored non-viral gene delivery systems, there still are many outstanding questions. A better characterisation of endocytic pathways would allow the diversion of cell adhesion processes and cytoskeletal dynamics, in order to increase cellular transfection. Further research on optimal biomaterial mechanical properties, cell ligand density and loading regimens is limited by the fact that such parameters influence a plethora of other different processes (e.g. cellular adhesion, spreading, migration, infiltration, and proliferation, DNA diffusion and release) which may in turn modulate gene delivery. Only a better understanding of these processes may allow the creation of novel robust engineered systems, potentially opening up a whole new area of biomaterial-guided gene delivery for non-viral systems.

Biotherapeutic-loaded injectable hydrogels as a synergistic strategy to support myocardial repair after myocardial infarction

Myocardial infarction (MI) has been considered as the leading cause of cardiovascular-related deaths worldwide. Although traditional therapeutic agents including various bioactive species such as growth factors, stem cells, and nucleic acids have demonstrated somewhat usefulness for the restoration of cardiac functions, the therapeutic efficiency remains unsatisfactory most likely due to the off-target-associated side effects and low localized retention of the used therapeutic agents in the infarcted myocardium, which constitutes a substantial barrier for the effective treatment of MI. Injectable hydrogels are regarded as a minimally invasive technology that can overcome the clinical and surgical limitations of traditional stenting by a modulated sol-gel transition and localized transport of a variety of encapsulated cargoes, leading to enhanced therapeutic efficiency and improved patient comfort and compliance. However, the design of injectable hydrogels for myocardial repair and the mechanism of action of bioactive substance-loaded hydrogels for MI repair remain unclear. To elucidate these points, we summarized the recent progresses made on the use of injectable hydrogels for encapsulation of various therapeutic substances for MI treatment with an emphasis on the mechanism of action of hydrogel systems for myocardial repair. Specifically, the pathogenesis of MI and the rational design of injectable hydrogels for myocardial repair were presented. Next, the mechanisms of various biotherapeutic substance-loaded injectable hydrogels for myocardial repair was discussed. Finally, the potential challenges and future prospects for the use of injectable hydrogels for MI treatment were proposed for the purpose of drawing theoretical guidance on the development of novel therapeutic strategies for efficient treatment of MI.

Preparation and in vitro characterization of histidine trimethyl chitosan conjugated nanocomplex incorporated into injectable thermosensitive hydrogels for localized gene delivery

Localized and sustained delivery of DNA using biomaterial scaffolds would increase the applicability of gene therapy in cancer treatment and tissue engineering. The most promising approach is the application of hydrogel scaffolds to encapsulate and deliver DNA in the form of nanocomplex to the target sites. In the present work, histidine conjugated trimethylated chitosan (HTMC) was synthesized and nanocomplexes fabricated with pDNA at different N/P ratios. The zeta potential and size of the HTMC/pDNA nanoparticles were determined using dynamic light scattering technique and the results were confirmed by scanning electron microscopy (SEM). The morphology of the nanoparticles was found spherical in shape having core-shell nanostructure. Based on gel retardation assay, polyplex dissociation following incubation with heparin, protection against DNase Ι, cytotoxicity and transfection experiments, HTMC/pDNA at N/P 15 was selected as an optimized formulation and loaded into CTS/PF127 and HA/PF127 hydrogel. The optimized HTMC/pDNA nanocomplex was homogenously distributed in the CTS/PF127 hydrogel. Transfection experiments were carried out on HEK293T cell lines and the results revealed that HTMC/pDNA complexes are stable and active inside the hydrogel, however, the transfection efficacy was decreased after incorporation into the hydrogel.

New Horizons in Hydrogels for Methotrexate Delivery

Since its first clinical application, methotrexate (MTX) has been widely used for the treatment of human diseases. Despite great advantages, some properties such as poor absorption, short plasma half-life and unpredictable bioavailability have led researchers to seek novel delivery systems to improve its characteristics for parenteral and oral administration. Recently, great attention has been directed to hydrogels for the preparation of MTX formulations. This review describes the potential of hydrogels for the formulation of MTX to treat cancer, rheumatoid arthritis, psoriasis and central nervous system diseases. We will delineate the state-of-the-art and promising potential of hydrogels for systemic MTX delivery as well as transdermal delivery of the drug-using hydrogel-based formulations.

Hydrogel-Based Localized Nonviral Gene Delivery in Regenerative Medicine Approaches-An Overview

Hydrogel-based nonviral gene delivery constitutes a powerful strategy in various regenerative medicine scenarios, as those concerning the treatment of musculoskeletal, cardiovascular, or neural tissues disorders as well as wound healing. By a minimally invasive administration, these systems can provide a spatially and temporarily defined supply of specific gene sequences into the target tissue cells that are overexpressing or silencing the original gene, which can promote natural repairing mechanisms to achieve the desired effect. In the present work, we provide an overview of the most avant-garde approaches using various hydrogels systems for controlled delivery of therapeutic nucleic acid molecules in different regenerative medicine approaches.

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.

Contact-Triggered Lipofection from Multilayer Films Designed as Surfaces for in Situ Transfection Strategies in Tissue Engineering

Biomaterials, which release active compounds after implantation, are an essential tool for targeted regenerative medicine. In this study, thin multilayer films loaded with lipid/DNA complexes (lipoplexes) were designed as surface coatings for in situ transfection applicable in tissue engineering and regenerative medicine. The film production and embedding of lipoplexes were based on the layer-by-layer (LbL) deposition technique. Hyaluronic acid (HA) and chitosan (CHI) were used as the polyelectrolyte components. The embedded plasmid DNA was complexed using a new designed cationic lipid formulation, namely, OH4/DOPE 1/1, the advantageous characteristics of which have been proven already. Three different methods were tested regarding its efficiency of lipid and DNA deposition. Therefore, several surface specific analytics were used to characterize the LbL formation, the lipid DNA embedding, and the surface characteristics of the multilayer films, such as fluorescence microscopy, surface plasmon resonance spectroscopy, ellipsometry, zeta potential measurements, atomic force microscopy, and scanning electron microscopy. Interaction studies were conducted for optimized lipoplex-loaded polyelectrolyte multilayers (PEMs) that showed an efficient attachment of C2C12 cells on the surface. Furthermore, no acute toxic effects were found in cell culture studies, demonstrating biocompatibility. Cell culture experiments with C2C12 cells, a cell line which is hard to transfect, demonstrated efficient transfection of the reporter gene encoding for green fluorescent protein. In vivo experiments using the chicken embryo chorion allantois membrane animal replacement model showed efficient gene-transferring rates in living complex tissues, although the DNA-loaded films were stored over 6 days under wet and dried conditions. Based on these findings, it can be concluded that OH4/DOPE 1/1 lipoplex-loaded PEMs composed of HA and CHI can be an efficient tool for in situ transfection in regenerative medicine.

Effective naked plasmid DNA delivery into stem cells by microextrusion-based transient-transfection system for in situ cardiac repair

BACKGROUND AIMS

Combining the use of transfection reagents and physical methods can markedly improve the efficiency of gene delivery; however, such methods often cause cell damage. Additionally, naked plasmids without any vector or physical stimulation are difficult to deliver into stem cells. In this study, we demonstrate a simple and rapid method to simultaneously facilitate efficient in situ naked gene delivery and form a bioactive hydrogel scaffold.

METHODS

Transfecting naked GATA binding protein 4 (GATA4) plasmids into human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) by co-extruding naked plasmids and hUC-MSCs with a biomimetic and negatively charged water-based biodegradable thermo-responsive polyurethane (PU) hydrogel through a microextrusion-based transient-transfection system can upregulate the other cardiac marker genes.

RESULTS

The PU hydrogels with optimized physicochemical properties (such as hard-soft segment composition, size, hardness and thermal gelation) induced GATA4-transfected hUC-MSCs to express the cardiac marker proteins and then differentiated into cardiomyocyte-like cells in 15 days. We further demonstrated that GATA4-transfected hUC-MSCs in PU hydrogel were capable of in situ revival of heart function in zebrafish in 30 days.

CONCLUSIONS

Our results suggest that hUC-MSCs and naked plasmids encapsulated in PU hydrogels might represent a new strategy for in situ tissue therapy using the microextrusion-based transient-transfection system described here. This transfection system is simple, effective and safer than conventional technologies.

A triple chain polycationic peptide-mimicking amphiphile - efficient DNA-transfer without co-lipids

Non-viral gene delivery in its current form is largely dependent upon the ability of a delivery vehicle to protect its cargo in the extracellular environment and release it efficiently inside the target cell. Also a simple delivery system is required to simplify a GMP conform production if a marketing authorization is striven for. This work addresses these problems. We have developed a synthetic polycationic peptide-mimicking amphiphile, namely DiTT4, which shows efficient transfection rates and good biocompatibility without the use of a co-lipid in the formulation. The lipid-nucleic acid complex (lipoplex) was characterized at the structural (electron microscopy), physical (laser Doppler velocimetry and atomic force microscopy) and molecular levels (X-ray scattering). Stability studies of the lipoplexes in the presence of serum and heparin indicated a stable formation capable of protecting the cargo against the extracellular milieu. Hemocompatibility studies (hemolysis, complement activation and erythrocyte aggregation) demonstrated the biocompatibility of the formulation for systemic administration. The transfection efficiency was assessed in vitro using the GFP assay and confocal laser scanning microscopy studies. With the chorioallantoic membrane model, an animal replacement model according to the 3R strategy (replacement, refinement, and reduction), initial in vivo experiments were performed which demonstrate fast and efficient transfection in complex tissues and excellent biocompatibility.

pH-responsive polymeric vesicles from branched copolymers

A new type of branched copolymer, poly(l-lactide)2-b-poly(l-glutamic acid) (PLLA2-PLGA), based on polypeptide PLGA is synthesized by the ring-opening polymerization (ROP) of N-carboxyanhydride of γ-benzyl-l-glutamate (BLG-NCA) with amino-terminated PLLA2-NH2 and subsequent deprotection. The branched copolymer is characterized by 1H NMR, FTIR and GPC measurements. The self-assembly of the copolymers in aqueous media has been systematically discussed. A pyrene probe has been used to demonstrate the aggregated formation of PLLA2-PLGA in solution by measuring the critical micelle concentration (cmc). The morphology and size of the micelles have further been studied by transmission electron microscopy (TEM), dynamic light scattering (DLS) and field emission scanning electron microscopy (ESEM). We demonstrated that the Rh of the vesicle is depending on solution pH and salt concentration. The vesicles show good stability with remained shapes and sizes during the lyophilizing process. These vesicles have great potential in the application of drug delivery.

Pathways Governing Polyethylenimine Polyplex Transfection in Microporous Annealed Particle Scaffolds

Gene delivery using injectable hydrogels can serve as a potential method for regulated tissue regeneration in wound healing. Our microporous annealed particle (MAP) hydrogel has been shown to promote cellular infiltration in both skin and brain wounds, while reducing inflammation. Although the scaffold itself can promote healing, it is likely that other signals will be required to promote healing of hard-to-treat wounds. Gene delivery is one approach to introduce desired bioactive signals. In this study, we investigated how the properties of MAP hydrogels influence non-viral gene delivery of polyethylenimine-condensed plasmid to cells seeded within the MAP gel. From past studies, we found that gene transfer to cells seeded in tissue culture plastic differed from gene transfer to cells seeded inside hydrogel scaffolds. Since MAP scaffolds are generated from hydrogel microparticles that are approximately 100 μm in diameter, they display local characteristics that can be viewed as two-dimensional or three-dimensional to cells. Thus, we sought to study if gene transfer inside MAP scaffolds differed from gene transfer to cells seeded in tissue culture plastic. We sought to understand the roles of the endocytosis pathway, actin and microtubule dynamics, RhoGTPases, and YAP/TAZ on transfection of human fibroblasts.

Biomaterial substrate modifications that influence cell-material interactions to prime cellular responses to nonviral gene delivery

IMPACT STATEMENT

This review summarizes how biomaterial substrate modifications (e.g. chemical modifications like natural coatings, ligands, or functional side groups, and/or physical modifications such as topography or stiffness) can prime the cellular response to nonviral gene delivery (e.g. affecting integrin binding and focal adhesion formation, cytoskeletal remodeling, endocytic mechanisms, and intracellular trafficking), to aid in improving gene delivery for applications where a cell-material interface might exist (e.g. tissue engineering scaffolds, medical implants and devices, sensors and diagnostics, wound dressings).

Injectable Biodegradable Chitosan-Alginate 3D Porous Gel Scaffold for mRNA Vaccine Delivery

mRNA vaccines have proven to be more stable, effective, and specific than protein/peptide-based vaccines in stimulating both humoral and cellular immune response. However, mRNA's fast degradation rate and low-transfection efficiency in vivo impede its potential in vaccination. Recent research in gene delivery has focused on nonviral vaccine carriers and either implantable or injectable delivery systems to improve transgene expression in vivo. Here, an injectable chitosan-alginate gel scaffold for the local delivery of mRNA vaccines is reported. Gel scaffold biodegradation rates and biocompatibility are quantified. Scaffold-mediated mRNA in vivo transgene expression as well as ovalbumin antigen specific cellular and humoral immune responses are evaluated in vivo. Luciferase reporter protein expression resulting from mRNA lipoplex-loaded gel scaffolds is five times higher than systemic injection. Compared to systemic injections of naked mRNA or mRNA:lipoplexes, elevated levels of T cell proliferation and IFN-γ secretion are seen with in vivo scaffold-mediated mRNA lipoplex delivery. Furthermore, a humoral response (ovalbumin antigen specific IgG levels) is observed as early as week 1 for scaffold-mediated mRNA lipoplex delivery, while protein-based immunization did not elicit IgG production until 2 weeks post-injection. Results suggest that injectable scaffold mRNA vaccine delivery maybe a viable alternative to traditional nucleic acid immunization methods.

In Situ Drug Delivery to Breast Cancer-Associated Extracellular Matrix

The extracellular matrix (ECM) contributes to tumor progression through changes induced by tumor and stromal cell signals that promote increased ECM density and stiffness. The increase in ECM stiffness is known to promote tumor cell invasion into surrounding tissues and metastasis. In addition, this scar-like ECM creates a protective barrier around the tumor that reduces the effectiveness of innate and synthetic antitumor agents. Herein, clinically approved breast cancer therapies as well as novel experimental approaches that target the ECM are discussed, including in situ hydrogel drug delivery systems, an emerging technology the delivers toxic chemotherapeutics, gene-silencing microRNAs, and tumor suppressing immune cells directly inside the tumor. Intratumor delivery of therapeutic agents has the potential to drastically reduce systemic side effects experienced by the patient and increase the efficacy of these agents. This review also describes the opposing effects of ECM degradation on tumor progression, where some studies report improved drug delivery and delayed cancer progression and others report enhanced metastasis and decreased patient survival. Given the recent increase in ECM-targeting drugs entering preclinical and clinical trials, understanding and addressing the factors that impact the effect of the ECM on tumor progression is imperative for the sake of patient safety and survival outcome.

It's All in the Delivery: Designing Hydrogels for Cell and Non-viral Gene Therapies

Hydrogels provide a regenerative medicine platform with their ability to create an environment that supports transplanted or endogenous infiltrating cells and enables these cells to restore or replace the function of tissues lost to disease or trauma. Furthermore, these systems have been employed as delivery vehicles for therapeutic genes, which can direct and/or enhance the function of the transplanted or endogenous cells. Herein, we review recent advances in the development of hydrogels for cell and non-viral gene delivery through understanding the design parameters, including both physical and biological components, on promoting transgene expression, cell engraftment, and ultimately cell function. Furthermore, this review identifies emerging opportunities for combining cell and gene delivery approaches to overcome challenges to the field.

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference.

Hyaluronic acid-based biopharmaceutical delivery and tumor-targeted drug delivery system

Hyaluronic acid (HA) is a natural polysaccharide with good biocompatibility and degradability. HA and its derivatives can be used as sustained-release carriers for drugs, which can delay the release of drugs and have a long-acting effect. They can be used for the delivery of various drugs such as proteins, nucleic acids and anti-tumor drugs. HA and its derivatives can specifically bind to multiple receptors on the cell surface and can be used for targeted drug delivery, especially for the delivery of anti-tumor drugs. Thus, there are different forms of tumor-targeted drug delivery systems based on HA.

Hydrogel-Assisted Antisense LNA Gapmer Delivery for In Situ Gene Silencing in Spinal Cord Injury

After spinal cord injury (SCI), nerve regeneration is severely hampered due to the establishment of a highly inhibitory microenvironment at the injury site, through the contribution of multiple factors. The potential of antisense oligonucleotides (AONs) to modify gene expression at different levels, allowing the regulation of cell survival and cell function, together with the availability of chemically modified nucleic acids with favorable biopharmaceutical properties, make AONs an attractive tool for novel SCI therapy developments. In this work, we explored the potential of locked nucleic acid (LNA)-modified AON gapmers in combination with a fibrin hydrogel bridging material to induce gene silencing in situ at a SCI lesion site. LNA gapmers were effectively developed against two promising gene targets aiming at enhancing axonal regeneration-RhoA and GSK3β. The fibrin-matrix-assisted AON delivery system mediated potent RNA knockdown in vitro in a dorsal root ganglion explant culture system and in vivo at a SCI lesion site, achieving around 75% downregulation 5 days after hydrogel injection. Our results show that local implantation of a AON-gapmer-loaded hydrogel matrix mediated efficient gene silencing in the lesioned spinal cord and is an innovative platform that can potentially combine gene regulation with regenerative permissive substrates aiming at SCI therapeutics and nerve regeneration.

Microgels produced using microfluidic on-chip polymer blending for controlled released of VEGF encoding lentivectors

Alginate hydrogels are widely used as delivery vehicles due to their ability to encapsulate and release a wide range of cargos in a gentle and biocompatible manner. The release of encapsulated therapeutic cargos can be promoted or stunted by adjusting the hydrogel physiochemical properties. However, the release from such systems is often skewed towards burst-release or lengthy retention. To address this, we hypothesized that the overall magnitude of burst release could be adjusted by combining microgels with distinct properties and release behavior. Microgel suspensions were generated using a process we have termed on-chip polymer blending to yield composite suspensions of a range of microgel formulations. In this manner, we studied how alginate percentage and degradation relate to the release of lentivectors. Whereas changes in alginate percentage had a minimal impact on lentivector release, microgel degradation led to a 3-fold increase, and near complete release, over 10 days. Furthermore, by controlling the amount of degradable alginate present within microgels the relative rate of release can be adjusted. A degradable formulation of microgels was used to deliver vascular endothelial growth factor (VEGF)-encoding lentivectors in the chick chorioallantoic membrane (CAM) assay and yielded a proangiogenic response in comparison to the same lentivectors delivered in suspension. The utility of blended microgel suspensions may provide an especially appealing platform for the delivery of lentivectors or similarly sized therapeutics.

STATEMENT OF SIGNIFICANCE

Genetic therapeutics hold considerable potential for the treatment of diseases and disorders including ischemic cardiovascular diseases. To realize this potential, genetic vectors must be precisely and efficiently delivered to targeted regions of the body. However, conventional methods of delivery do not provide sufficient spatial and temporal control. Here, we demonstrate how alginate microgels provide a basis for developing systems for controlled genetic vector release. We adjust the physiochemical properties of alginate for quicker or slower release, and we demonstrate how combining distinct formulations of microgels can tune the release of the overall composite microgel suspension. These composite suspensions are generated using a straightforward and powerful application of droplet microfluidics which allows for the real-time generation of a composite suspension.

Sustained micellar delivery via inducible transitions in nanostructure morphology

Nanocarrier administration has primarily been restricted to intermittent bolus injections with limited available options for sustained delivery in vivo. Here, we demonstrate that cylinder-to-sphere transitions of self-assembled filomicelle (FM) scaffolds can be employed for sustained delivery of monodisperse micellar nanocarriers with improved bioresorptive capacity and modularity for customization. Modular assembly of FMs from diverse block copolymer (BCP) chemistries allows in situ gelation into hydrogel scaffolds following subcutaneous injection into mice. Upon photo-oxidation or physiological oxidation, molecular payloads within FMs transfer to micellar vehicles during the morphological transition, as verified in vitro by electron microscopy and in vivo by flow cytometry. FMs composed of multiple distinct BCP fluorescent conjugates permit multimodal analysis of the scaffold's non-inflammatory bioresorption and micellar delivery to immune cell populations for one month. These scaffolds exhibit highly efficient bioresorption wherein all components participate in retention and transport of therapeutics, presenting previously unexplored mechanisms for controlled nanocarrier delivery.

Tissue engineering; strategies, tissues, and biomaterials

Current tissue regenerative strategies rely mainly on tissue repair by transplantation of the synthetic/natural implants. However, limitations of the existing strategies have increased the demand for tissue engineering approaches. Appropriate cell source, effective cell modification, and proper supportive matrices are three bases of tissue engineering. Selection of appropriate methods for cell stimulation, scaffold synthesis, and tissue transplantation play a definitive role in successful tissue engineering. Although the variety of the players are available, but proper combination and functional synergism determine the practical efficacy. Hence, in this review, a comprehensive view of tissue engineering and its different aspects are investigated.

Polymers and hydrogels for local nucleic acid delivery

This review focusses on the rational design of materials (from polymers to hydrogel materials) to achieve successful local delivery of therapeutic nucleic acids.

The Physiological and Pathological Implications of the Formation of Hydrogels, with a Specific Focus on Amyloid Polypeptides

Hydrogels are water-swollen and viscoelastic three-dimensional cross-linked polymeric network originating from monomer polymerisation. Hydrogel-forming polypeptides are widely found in nature and, at a cellular and organismal level, they provide a wide range of functions for the organism making them. Amyloid structures, arising from polypeptide aggregation, can be damaging or beneficial to different types of organisms. Although the best-known amyloids are those associated with human pathologies, this underlying structure is commonly used by higher eukaryotes to maintain normal cellular activities, and also by microbial communities to promote their survival and growth. Amyloidogenesis occurs by nucleation-dependent polymerisation, which includes several species (monomers, nuclei, oligomers, and fibrils). Oligomers of pathological amyloids are considered the toxic species through cellular membrane perturbation, with the fibrils thought to represent a protective sink for toxic species. However, both functional and disease-associated amyloids use fibril cross-linking to form hydrogels. The properties of amyloid hydrogels can be exploited by organisms to fulfil specific physiological functions. Non-physiological hydrogelation by pathological amyloids may provide additional toxic mechanism(s), outside of membrane toxicity by oligomers, such as physical changes to the intracellular and extracellular environments, with wide-spread consequences for many structural and dynamic processes, and overall effects on cell survival.