Hydrogels for protein delivery

Development of a local controlled release system for therapeutic proteins in the treatment of skeletal muscle injuries and diseases

The present study aims to develop and characterize a controlled-release delivery system for protein therapeutics in skeletal muscle regeneration following an acute injury. The therapeutic protein, a membrane-GPI anchored protein called Cripto, was immobilized in an injectable hydrogel delivery vehicle for local administration and sustained release. The hydrogel was made of poly(ethylene glycol)-fibrinogen (PEG-Fibrinogen, PF), in the form of injectable microspheres. The PF microspheres exhibited a spherical morphology with an average diameter of approximately 100 micrometers, and the Cripto protein was uniformly entrapped within them. The release rate of Cripto from the PF microspheres was controlled by tuning the crosslinking density of the hydrogel, which was varied by changing the concentration of poly(ethylene glycol) diacrylate (PEG-DA) crosslinker. In vitro experiments confirmed a sustained-release profile of Cripto from the PF microspheres for up to 27 days. The released Cripto was biologically active and promoted the in vitro proliferation of mouse myoblasts. The therapeutic effect of PF-mediated delivery of Cripto in vivo was tested in a cardiotoxin (CTX)-induced muscle injury model in mice. The Cripto caused an increase in the in vivo expression of the myogenic markers Pax7, the differentiation makers eMHC and Desmin, higher numbers of centro-nucleated myofibers and greater areas of regenerated muscle tissue. Collectively, these results establish the PF microspheres as a potential delivery system for the localized, sustained release of therapeutic proteins toward the accelerated repair of damaged muscle tissue following acute injuries.

Dual encapsulation and sequential release of cisplatin and vitamin E from soy polysaccharides and β-cyclodextrin bioadhesive hydrogel nanoparticles

Chemically cross-linked hydrogel nanoparticles (HGNPs) offer enhanced properties over their physical counterparts, particularly in drug delivery and cell encapsulation. This study applied pH-thermal dual responsive bio-adhesive HGNPs for dual complexation and enhanced the controlled release and bioavailability of cisplatin (CDDP) and Vitamin E (VE) drugs. The CDDP was loaded into the HGNPs via chemical conjugation with the carboxyl groups in the HGNPs surface by soy polysaccharides (SSPS). At the same time, the host-guest interaction complexed the VE through the β-cyclodextrin (β-CD). The HGNPs showed a uniform HGNPs size distribution of 90.77 ± 14.77 nm and 81.425 ± 13.21 nm before and after complexation, respectively. The FTIR, XRD, XPS, and zeta potential confirmed the conjugation. The cumulative release percent of CDDP reached 98 % at pH 1.2, while <45 % was released at pH 7.4. Our HGNPs enhance the incorporation of CDDP by substituting its chlorides with carboxyl groups of the SSPS; the loading of CDDP and VE was 15 ± 0.33 and 11.32 ± 0.25 wt%, respectively. Moreover, the CDDP and VE also released slower from the HGNPs at 25 °C than at 37 °C and 42 °C. The (VE/CDDP)-loaded HGNPs exhibited longer circulation time in vivo than free CDDP and free VE suspension.

Carboxymethyl chitosan-methacrylic acid gelatin hydrogel for wound healing and vascular regeneration

At present, wound dressings in clinical applications are primarily used for superficial skin wounds. However, these dressings have significant limitations, including poor biocompatibility and limited ability to promote wound healing. To address the issue, this study used aldehyde polyethylene glycol as the cross-linking agent to design a carboxymethyl chitosan-methacrylic acid gelatin hydrogel with enhanced biocompatibility, which can promote wound healing and angiogenesis. The CSDG hydrogel exhibits acid sensitivity, with a swelling ratio of up to 300%. Additionally, it exhibited excellent resistance to external stress, withstanding pressures of up to 160 kPa and self-deformation of 80%. Compared to commercially available chitosan wound gels, the CSDG hydrogel demonstrates excellent biocompatibility, antibacterial properties, and hemostatic ability. Bothin vitroandin vivoresults showed that the CSDG hydrogel accelerated blood vessel regeneration by upregulating the expression of CD31, IL-6, FGF, and VEGF, thereby promoting rapid healing of wounds. In conclusion, this study successfully prepared the CSDG hydrogel wound dressings, providing a new approach and method for the development of hydrogel dressings based on natural macromolecules.

A Bionic Thermosensitive Sustainable Delivery System for Reversing the Progression of Osteoarthritis by Remodeling the Joint Homeostasis

Although the pathogenesis of osteoarthritis (OA) is unclear, inflammatory cytokines are related to its occurrence. However, few studies focused on the therapeutic strategies of regulating joint homeostasis by simultaneously remodeling the anti-inflammatory and immunomodulatory microenvironments. Fibroblast growth factor 18 (FGF18) is the only disease-modifying OA drug (DMOAD) with a potent ability and high efficiency in maintaining the phenotype of chondrocytes within cell culture models. However, its potential role in the immune microenvironment remains unknown. Besides, information on an optimal carrier, whose interface and chondral-biomimetic microenvironment mimic the native articular tissue, is still lacking, which substantially limits the clinical efficacy of FGF18. Herein, to simulate the cartilage matrix, chondroitin sulfate (ChS)-based nanoparticles (NPs) are integrated into poly(D, L-lactide)-poly(ethylene glycol)-poly(D, L-lactide) (PLEL) hydrogels to develop a bionic thermosensitive sustainable delivery system. Electrostatically self-assembled ChS and ε-poly-l-lysine (EPL) NPs are prepared for the bioencapsulation of FGF18. This bionic delivery system suppressed the inflammatory response in interleukin-1β (IL-1β)-mediated chondrocytes, promoted macrophage M2 polarization, and inhibited M1 polarization, thereby ameliorating cartilage degeneration and synovitis in OA. Thus, the ChS-based hydrogel system offers a potential strategy to regulate the chondrocyte-macrophage crosstalk, thus re-establishing the anti-inflammatory and immunomodulatory microenvironment for OA therapy.

Recent Advances in Smart Self-Assembled Bioinspired Hydrogels: A Bridging Weapon for Emerging Health Care Applications from Bench to Bedside

Stimuli-responsive low molecular weight hydrogel interventions for Biomedical challenges are a rapidly evolving paradigm in the bottom-up approach recently. Peptide-based self-assembled nano biomaterials present safer alternatives to their non-degradable counterparts as demanded for today's most urged clinical needs.Although a plethora of work has already been accomplished, programming hydrogelators with appropriate functionalities requires a better understanding as the impact of the macromolecular structure of the peptides and subsequently, their self-assembled nanostructures remain unidentified. Henceforth this review focuses on two aspects: Firstly, the underlying guidelines for building biomimetic strategies to tailor scaffolds leading to hydrogelation along with the role of non-covalent interactions that are the key components of various self-assembly processes. In the second section, it is aimed to bring together the recent achievements with designer assembly concerning their self-aggregation behaviour and applications mainly in the biomedical arena like drug delivery carrier design, antimicrobial, anti-inflammatory as well as wound healing materials. Furthermore, it is anticipated that this article will provide a conceptual demonstration of the different approaches taken towards the construction of these task-specific designer hydrogels. Finally, a collective effort among the material scientists is required to pave the path for the entrance of these intelligent materials into medicine from bench to bedside.

Brain Delivery of Protein Therapeutics by Cell Matrix-Inspired Biomimetic Nanocarrier

Protein therapeutics are anticipated to offer significant treatment options for central nervous system (CNS) diseases. However, the majority of proteins are unable to traverse the blood-brain barrier (BBB) and reach their CNS target sites. Inspired by the natural environment of active proteins, the cell matrix components hyaluronic acid (HA) and protamine (PRTM) are used to self-assemble with proteins to form a protein-loaded biomimetic core and then incorporated into ApoE3-reconstituted high-density lipoprotein (rHDL) to form a protein-loaded biomimetic nanocarrier (Protein-HA-PRTM-rHDL). This cell matrix-inspired biomimetic nanocarrier facilitates the penetration of protein therapeutics across the BBB and enables their access to intracellular target sites. Specifically, CAT-HA-PRTM-rHDL facilitates rapid intracellular delivery and release of catalase (CAT) via macropinocytosis-activated membrane fusion, resulting in improved spatial learning and memory in traumatic brain injury (TBI) model mice (significantly reduces the latency of TBI mice and doubles the number of crossing platforms), and enhances motor function and prolongs survival in amyotrophic lateral sclerosis (ALS) model mice (extended the median survival of ALS mice by more than 10 days). Collectively, this cell matrix-inspired nanoplatform enables the efficient CNS delivery of protein therapeutics and provides a novel approach for the treatment of CNS diseases.

Degradable, anti-swelling, high-strength cellulosic hydrogels via salting-out and ionic coordination

Cellulosic hydrogels are widely used in various applications, as they are natural raw materials and have excellent degradability. However, their poor mechanical properties restrict their practical application. This study presents a facile approach for fabricating cellulosic hydrogels with high strength by synergistically utilizing salting-out and ionic coordination, thereby inducing the collapse and aggregation of cellulose chains to form a cross-linked network structure. Cellulosic hydrogels are prepared by soaking cellulose in an Al2(SO4)3 solution, which is both strong (compressive strength of up to 16.99 MPa) and tough (compressive toughness of up to 2.86 MJ/m3). The prepared cellulosic hydrogels exhibit resistance to swelling in different solutions and good biodegradability in soil. The cellulosic hydrogels are incorporated into strain sensors for human-motion monitoring by introducing AgNWs. Thus, the study offers a promising, simple, and scalable approach for preparing strong, degradable, and anti-swelling hydrogels using common biomass resources with considerable potential for various applications.

Injectable Hydrogels: A Paradigm Tailored with Design, Characterization, and Multifaceted Approaches

Biomaterials denoting self-healing and versatile structural integrity are highly curious in the biomedicine segment. The injectable and/or printable 3D printing technology is explored in a few decades back, which can alter their dimensions temporarily under shear stress, showing potential healing/recovery tendency with patient-specific intervention toward the development of personalized medicine. Thus, self-healing injectable hydrogels (IHs) are stunning toward developing a paradigm for tissue regeneration. This review comprises the designing of IHs, rheological characterization and stability, several benchmark consequences for self-healing IHs, their translation into tissue regeneration of specific types, applications of IHs in biomedical such as anticancer and immunomodulation, wound healing and tissue/bone regeneration, antimicrobial potentials, drugs, gene and vaccine delivery, ocular delivery, 3D printing, cosmeceuticals, and photothermal therapy as well as in other allied avenues like agriculture, aerospace, electronic/electrical industries, coating approaches, patents associated with therapeutic/nontherapeutic avenues, and numerous futuristic challenges and solutions.

In-Hydrogel Cell-Free Protein Expression System as Biocompatible and Implantable Biomaterial

Biomaterials capable of delivering therapeutic proteins are relevant in biomedicine, yet their manufacturing relies on centralized manufacturing chains that pose challenges to their remote implementation at the point of care. This study explores the viability of confined cell-free protein synthesis within porous hydrogels as biomaterials that dynamically produce and deliver proteins to in vitro and in vivo biological microenvironments. These functional biomaterials have the potential to be assembled as implants at the point of care. To this aim, we first entrap cell-free extracts (CFEs) from Escherichia coli containing the transcription-translation machinery, together with plasmid DNA encoding the super folded green fluorescence protein (sGFP) as a model protein, into hydrogels using various preparation methods. Agarose hydrogels result in the most suitable biomaterials to confine the protein synthesis system, demonstrating efficient sGFP production and diffusion from the core to the surface of the hydrogel. Freeze-drying (FD) of agarose hydrogels still allows for the synthesis and diffusion of sGFP, yielding a more attractive biomaterial for its reconstitution and implementation at the point of care. FD-agarose hydrogels are biocompatible in vitro, allowing for the colonization of cell microenvironments along with cell proliferation. Implantation assays of this biomaterial in a preclinical mouse model proved the feasibility of this protein synthesis approach in an in vivo context and indicated that the physical properties of the biomaterials influence their immune responses. This work introduces a promising avenue for biomaterial fabrication, enabling the in vivo synthesis and targeted delivery of proteins and opening new paths for advanced protein therapeutic approaches based on biocompatible biomaterials.

Mussel inspired sequential protein delivery based on self-healing injectable nanocomposite hydrogel

Polysaccharide based self-healing and injectable hydrogels with reversible characteristics have widespread potential in protein drug delivery. However, it is a challenge to design the dynamic hydrogel for sequential release of protein drugs. Herein, we developed a novel mussel inspired sequential protein delivery dynamic polysaccharide hydrogel. The nanocomposite hydrogel can be fabricated through doping polydopamine nanoparticles (PDA NPs) into reversible covalent bond (imine bonds) crosslinked polymer networks of oxidized hyaluronic acid (OHA) and carboxymethyl chitosan (CEC), named PDA NPs@OHA-l-CEC. Besides multiple capabilities (i.e., injection, self-healing, and biodegradability), the nanocomposite hydrogel can achieve sustained and sequential protein delivery of vascular endothelial growth factor (VEGF) and bovine serum albumin (BSA). PDA NPs doped in hydrogel matrix serve dual roles, acting as secondary protein release structures and form dynamic non-covalent interactions (i.e., hydrogen bonds) with polysaccharides. Moreover, by adjusting the oxidation degree of OHA, the hydrogels with different crosslinking density could control overall protein release rate. Analysis of different release kinetic models revealed that Fickian diffusion drove rapid VEGF release, while the slower BSA release followed a Super Case II transport mechanism. The novel biocompatible system achieved sequential release of protein drugs has potentials in multi-stage synergistic drug deliver based on dynamic hydrogel.

Covalent Grafting of Functionalized MEW Fibers to Silk Fibroin Hydrogels to Obtain Reinforced Tissue Engineered Constructs

Hydrogels are ideal materials to encapsulate cells, making them suitable for applications in tissue engineering and regenerative medicine. However, they generally do not possess adequate mechanical strength to functionally replace human tissues, and therefore they often need to be combined with reinforcing structures. While the interaction at the interface between the hydrogel and reinforcing structure is imperative for mechanical function and subsequent biological performance, this interaction is often overlooked. Melt electrowriting enables the production of reinforcing microscale fibers that can be effectively integrated with hydrogels. Yet, studies on the interaction between these micrometer scale fibers and hydrogels are limited. Here, we explored the influence of covalent interfacial interactions between reinforcing structures and silk fibroin methacryloyl hydrogels (silkMA) on the mechanical properties of the construct and cartilage-specific matrix production in vitro. For this, melt electrowritten fibers of a thermoplastic polymer blend (poly(hydroxymethylglycolide-co-ε-caprolactone):poly(ε-caprolactone) (pHMGCL:PCL)) were compared to those of the respective methacrylated polymer blend pMHMGCL:PCL as reinforcing structures. Photopolymerization of the methacrylate groups, present in both silkMA and pMHMGCL, was used to generate hybrid materials. Covalent bonding between the pMHMGCL:PCL blend and silkMA hydrogels resulted in an elastic response to the application of torque. In addition, an improved resistance was observed to compression (∼3-fold) and traction (∼40-55%) by the scaffolds with covalent links at the interface compared to those without these interactions. Biologically, both types of scaffolds (pHMGCL:PCL and pMHMGCL:PCL) showed similar levels of viability and metabolic activity, also compared to frequently used PCL. Moreover, articular cartilage progenitor cells embedded within the reinforced silkMA hydrogel were able to form a cartilage-like matrix after 28 days of in vitro culture. This study shows that hybrid cartilage constructs can be engineered with tunable mechanical properties by grafting silkMA hydrogels covalently to pMHMGCL:PCL blend microfibers at the interface.

Statistical optimization of hydrazone-crosslinked hyaluronic acid hydrogels for protein delivery

Hydrazone-crosslinked hydrogels are attractive protein delivery vehicles for regenerative medicine. However, each regenerative medicine application requires unique hydrogel properties to achieve an ideal outcome. The properties of a hydrogel can be impacted by numerous factors involved in its fabrication. We used design of experiments (DoE) statistical modeling to efficiently optimize the physicochemical properties of a hyaluronic acid (HA) hydrazone-crosslinked hydrogel for protein delivery for bone regeneration. We modified HA with either adipic acid dihydrazide (HA-ADH) or aldehyde (HA-Ox) functional groups and used DoE to evaluate the interactions of three input variables, the molecular weight of HA (40 or 100 kDa), the concentration of HA-ADH (1-3% w/v), and the concentration of HA-Ox (1-3% w/v), on three output responses, gelation time, compressive modulus, and hydrogel stability over time. We identified 100 kDa HA-ADH3.00HA-Ox2.33 as an optimal hydrogel that met all of our design criteria, including displaying a gelation time of 3.7 minutes, compressive modulus of 62.1 Pa, and minimal mass change over 28 days. For protein delivery, we conjugated affinity proteins called affibodies that were specific to the osteogenic protein bone morphogenetic protein-2 (BMP-2) to HA hydrogels and demonstrated that our platform could control the release of BMP-2 over 28 days. Ultimately, our approach demonstrates the utility of DoE for optimizing hydrazone-crosslinked HA hydrogels for protein delivery.

Impact of Confinement within a Hydrogel Mesh on Protein Thermodynamic Stability and Aggregation Kinetics

Though protein stability and aggregation have been well characterized in dilute solutions, the influence of a confining environment that exists (e.g., in intercellular and tissue spaces and therapeutic formulations) on the protein structure is largely unknown. Herein, the effects of confinement on stability and aggregation were explored for proteins of different sizes, stability, and hydrophobicity when encapsulated in hydrophilic poly(ethylene glycol) hydrogels. Denaturation curves show linear correlations between confinement size (mesh size) and thermodynamic stability, i.e., unfolding free energy and surface area accessible for solvation (represented by m-value). Two clusters of protein types are identifiable from these correlations; the clusters are defined by differences in protein stability, surface area, and aggregation propensity. Proteins with higher stability, larger surface area, and lower aggregation propensity (e.g., lysozyme and myoglobin) are less affected by the confinement imposed by mesh size than proteins with lower stability, smaller surface area, and higher aggregation propensity (e.g., growth hormone and aldehyde dehydrogenase). According to aggregation kinetics measured by thioflavin T fluorescence, confinement in smaller mesh sizes resulted in slower aggregation rates than that in larger mesh sizes. Compared to that in buffer solution, the confinement of a hydrophobic protein (e.g., human insulin) in the hydrogels accelerates protein aggregation. Conversely, the confinement of a hydrophilic protein (e.g., human amylin) in the hydrogels decelerates or prevents aggregation, with the rates of aggregation inversely proportional to mesh size. These findings provide new insights into protein conformational stability in confined microenvironments relevant to various cellular, tissue, and therapeutics scenarios.

Elastic Macroporous Matrix-Supported In Situ Formation of Injectable Extracellular Matrix-Like Hydrogel for Carrying Growth Factors and Living Cells

Hydrogels loaded with biologics hold great potential for various biomedical applications such as regenerative medicine. However, biologics may lose bioactivity during hydrogel preparation, shipping, and storage. While many injectable hydrogels do not have this issue, they face a dilemma between fast gelation causing the difficulty of injection and slow gelation causing the escape of solutions from an injection site. The purpose of this study is to develop an affinity hydrogel by integrating a pre-formed elastic macroporous matrix and an injectable hydrogel. The data shows that the macroporous hydrogel matrix can hold a large volume of solutions for the formation of in situ injectable hydrogels loaded with growth factors or living cells. The cells can proliferate in the composite hydrogels. The growth factors can be stably sequestered and sustainably released due to the presence of aptamers. When both living cells and growth factors are loaded together into the hydrogels, cells can proliferate under culture conditions with a reduced serum level. Therefore, a macroporous and elastic matrix-supported formation of aptamer-functionalized injectable hydrogels is a promising method for developing the carriers of biologics.

Injectable, Adhesive Albumin Nanoparticle-Incorporated Hydrogel for Sustained Localized Drug Delivery and Efficient Tumor Treatment

Injectable hydrogels are receiving increasing attention as local depots for sustained anticancer drug delivery. However, most current hydrogel-based carriers lack tissue-adhesive ability, a property that is important for the immobilization of drug-loaded systems at tumor sites to increase local drug concentration. In this study, we developed a paclitaxel (PTX)-loaded injectable hydrogel with firm tissue adhesion for localized tumor therapy. PTX-loaded bovine serum albumin (BSA) nanoparticles (PTX@BN) were prepared, and the drug-loaded hydrogel was then fabricated by cross-linking PTX@BN with o-phthalaldehyde (OPA)-terminated 4-armed poly(ethylene glycol) (4aPEG-OPA) via a condensation reaction between OPA and the amines in BSA. The hydrogel showed firm adhesion to various organs and tumor tissues ex vivo due to the condensation reaction of unreacted OPA groups and amines in the tissues. The PTX-loaded nanocomposite hydrogels sustained PTX release over 30 days following the Korsmeyer-Peppas model and exhibited notable inhibition activities against mouse C26 colon and 4T1 breast cancer cells in vitro. Following peritumoral injection into mice with C26 or 4T1 tumors, the PTX@BN-loaded hydrogel significantly enhanced the antitumor efficacy and prolonged animal survival time compared to free PTX solutions with low systemic toxicity. Therefore, the adhesive, PTX-loaded nanocomposite hydrogels have the potential for efficient localized tumor therapy.

Injectable hydrogels as emerging drug-delivery platforms for tumor therapy

Tumor therapy continues to be a prominent field within biomedical research. The development of various drug carriers has been propelled by concerns surrounding the side effects and targeting efficacy of various chemotherapeutic drugs and other therapeutic agents. These carriers strive to enhance drug concentration at tumor sites, minimize systemic side effects, and improve therapeutic outcomes. Among the reported delivery systems, injectable hydrogels have emerged as an emerging candidate for the in vivo delivery of chemotherapeutic drugs due to their minimal invasive drug delivery properties. This review systematically summarizes the composition and preparation methodologies of injectable hydrogels and further highlights the delivery mechanisms of diverse drugs using these hydrogels for tumor therapy, along with an in-depth discussion on the optimized therapeutic efficiency of drugs encapsulated within the hydrogels. The work concludes by providing a dynamic forward-looking perspective on the potential challenges and possible solutions of the in situ injectable hydrogels for non-surgical and real-time diagnostic applications.

Albumin Hydrogel-Coated Mesoporous Silica Nanoparticle as a Carrier of Cationic Porphyrin and Ratiometric Fluorescence pH Sensor

Here, we report that a mesoporous silica nanoparticle (MSN) coated with a fluoresceine-labeled bovine serum albumin (F-BSA) hydrogel layer works as a temperature-responsive nanocarrier for tetrakis-N-methylpyridyl porphyrin (TMPyP) and as a fluorescence ratiometric pH probe. F-BSA hydrogel-coated MSN containing TMPyP (F-BSA/MSN/TMPyP) was synthesized by thermal gelation of denatured F-BSA on the external surface of MSN. The F-BSA hydrogel layer was composed of an inner hard corona layer and an outer soft layer and was stable under physiological conditions. F-BSA/MSN/TMPyP exhibited temperature-dependent exponential release of TMPyP. In this release profile, the MSN was found to be a suitable host for stable encapsulation of tetracationic TMPyP by electrostatic interactions, and the F-BSA hydrogel layer mediated the diffusion of TMPyP from the MSN pore interior into the solution phase. Increasing temperature promoted partitioning of TMPyP from the pore interior to the F-BSA hydrogel layer, from where it was spontaneously released into the bulk solution phase by cation exchange. F-BSA/MSN/TMPyP also gave a linear ratiometric fluorescence response (1.3 per pH unit) in the pH range from 6.1 to 8.9.

G-POSS connected double network starch gels for protein release

Starch is one of the most frequently preferred natural polymers in hydrogel synthesis. Herein, we combined two strategies of associating brittle and ductile networks in a structure and incorporating inorganic particles into the polymeric gel to design mechanically enhanced nanocomposite double network (DN) starch gels. For the first time in the literature, nanocomposite starch gels (s-NC) were designed by cross-linking starch chains with 8-armed glycidyl-polyhedral oligomeric silsesquioxane (g-POSS) units. Fourier Transform Infrared Spectroscopy and Energy Dispersive X-Ray Spectroscopy analyses have proven that g-POSS is included in the gel structure and is homogeneously distributed throughout the network. More stable d-NC-DMA and d-NC-VP gels were obtained by incorporating N,N-dimethylacrylamide (DMA), or 1-vinyl-2-pyrrolidinone (VP) units, respectively, into g-POSS-linked starch gels, and the reaction kinetics were followed in situ. In SEM images, it was observed that d-NC-DMA had smaller pores and thicker pore walls compared to s-NC and d-NC-VP starch gels, and its mechanical strength was shown to be much superior by rheological tests, compression, and tensile analyses. In addition to increasing the mechanical strength of the gels, the potential of starch in protein release applications using amylase sensitivity has been demonstrated in vitro experiments using the model protein BSA.

Rational design of viscoelastic hydrogels for periodontal ligament remodeling and repair

The periodontal ligament (PDL) is a distinctive yet critical connective tissue vital for maintaining the integrity and functionality of tooth-supporting structures. However, PDL repair poses significant challenges due to the complexity of its mechanical microenvironment encompassing hard-soft-hard tissues, with the viscoelastic properties of the PDL being of particular interest. This review delves into the significant role of viscoelastic hydrogels in PDL regeneration, underscoring their utility in simulating biomimetic three-dimensional microenvironments. We review the intricate relationship between PDL and viscoelastic mechanical properties, emphasizing the role of tissue viscoelasticity in maintaining mechanical functionality. Moreover, we summarize the techniques for characterizing PDL's viscoelastic behavior. From a chemical bonding perspective, we explore various crosslinking methods and characteristics of viscoelastic hydrogels, along with engineering strategies to construct viscoelastic cell microenvironments. We present a detailed analysis of the influence of the viscoelastic microenvironment on cellular mechanobiological behavior and fate. Furthermore, we review the applications of diverse viscoelastic hydrogels in PDL repair and address current challenges in the field of viscoelastic tissue repair. Lastly, we propose future directions for the development of innovative hydrogels that will facilitate not only PDL but also systemic ligament tissue repair. STATEMENT OF SIGNIFICANCE.

Designing Composite Stimuli-Responsive Hydrogels for Wound Healing Applications: The State-of-the-Art and Recent Discoveries

Effective wound treatment has become one of the most important challenges for healthcare as it continues to be one of the leading causes of death worldwide. Therefore, wound care technologies significantly evolved in order to provide a holistic approach based on various designs of functional wound dressings. Among them, hydrogels have been widely used for wound treatment due to their biocompatibility and similarity to the extracellular matrix. The hydrogel formula offers the control of an optimal wound moisture level due to its ability to absorb excess fluid from the wound or release moisture as needed. Additionally, hydrogels can be successfully integrated with a plethora of biologically active components (e.g., nanoparticles, pharmaceuticals, natural extracts, peptides), thus enhancing the performance of resulting composite hydrogels in wound healing applications. In this review, the-state-of-the-art discoveries related to stimuli-responsive hydrogel-based dressings have been summarized, taking into account their antimicrobial, anti-inflammatory, antioxidant, and hemostatic properties, as well as other effects (e.g., re-epithelialization, vascularization, and restoration of the tissue) resulting from their use.

Advanced Formulation Approaches for Proteins

Proteins and peptides are highly desirable as therapeutic agents, being highly potent and specific. However, there are myriad challenges with processing them into patient-friendly formulations: they are often unstable and have a tendency to aggregate or degrade upon storage. As a result, the vast majority of protein actives are delivered parenterally as solutions, which has a number of disadvantages in terms of cost, accessibility, and patient experience. Much work has been undertaken to develop new delivery systems for biologics, but to date this has led to relatively few products on the market. In this chapter, we review the challenges faced when developing biologic formulations, discuss the technologies that have been explored to try to overcome these, and consider the different delivery routes that can be applied. We further present an overview of the currently marketed products and assess the likely direction of travel in the next decade.

Rational Design and Development of Polymeric Nanogels as Protein Carriers

Proteins have gained significant attention as potential therapeutic agents owing to their high specificity and reduced toxicity. Nevertheless, their clinical utility is hindered by inherent challenges associated with stability during storage and after in vivo administration. To overcome these limitations, polymeric nanogels (NGs) have emerged as promising carriers. These colloidal systems are capable of efficient encapsulation and stabilization of protein cargoes while improving their bioavailability and targeted delivery. The design of such delivery systems requires a comprehensive understanding of how the synthesis and formulation processes affect the final performance of the protein. This review highlights critical aspects involved in the development of NGs for protein delivery, with specific emphasis on loading strategies and evaluation techniques. For example, factors influencing loading efficiency and release kinetics are discussed, along with strategies to optimize protein encapsulation through protein-carrier interactions to achieve the desired therapeutic outcomes. The discussion is based on recent literature examples and aims to provide valuable insights for researchers working toward the advancement of protein-based therapeutics.

Dendronization of chitosan to afford unprecedent thermoresponsiveness and tunable microconfinement

Convenient chemical modification of biomacromolecules to create novel biocompatible functional materials satisfies the current requirements of sustainable chemistry. Dendronization of chitosan with dendritic oligoethylene glycols (OEGs) paves a strategy for the preparation of functional dendronized chitosans (DCSs) with unprecedent thermoresponsive behavior, which inherit biological features from polysaccharides and the topological features from dendritic OEGs. In addition, densely packed dendritic OEG chains around the backbone provide efficient cooperative interactions and form an intriguing confined microenvironment based on the degradable biopolymers. In this perspective, we describe the principle for the preparation of the thermoresponsive DCSs, and focus on the molecular envelop effect from the hydrophobic microconfinement to the encapsulated guest molecules or moieties. Particular attention is put on their capacity to regulate behavior and the functions of the encapsulated guests through thermally-mediated dehydration and collapse of the densely packed dendritic OEGs. We believe that the methodology described here may provide prospects for the fabrication of functional materials from biomacromolecules, especially when used as environmentally friendly nanomaterials or in accurate diagnosis and therapy.

An Overview of Supramolecular Platforms Boosting Drug Delivery

Numerous supramolecular platforms inspired by natural self-assembly are exploited as drug delivery systems. The spontaneous arrangement of single building blocks into inorganic and organic structures is determined and controlled by noncovalent forces such as electrostatic interactions, π-π interactions, hydrogen bonds, and van der Waals interactions. This review describes the main structures and characteristics of several building blocks used to obtain stable, self-assembling nanostructures tailored for numerous biological applications. Owing to their versatility, biocompatibility, and controllability, these nanostructures find application in diverse fields ranging from drug/gene delivery, theranostics, tissue engineering, and nanoelectronics. Herein, we described the different approaches used to design and functionalize these nanomaterials to obtain selective drug delivery in a specific disease. In particular, the review highlights the efficiency of these supramolecular structures in applications related to infectious diseases and cancer.

Nanoengineered injectable hydrogels derived from layered double hydroxides and alginate for sustained release of protein therapeutics in tissue engineering applications

Chronic Kidney Disease (CKD) which involves gradual loss of kidney function is characterized by low levels of a glycoprotein called Erythropoietin (EPO) that leads to red blood cell  deficiency and anemia. Recombinant human EPO (rhEPO) injections that are administered intravenously or subcutaneously is the current gold standard for treating CKD. The rhEPO injections have very short half-lives and thus demands frequent administration with a risk of high endogenous EPO levels leading to severe side effects that could prove fatal. To this effect, this work provides a novel approach of using lamellar inorganic solids with a brucite-like structure for controlling the release of protein therapeutics such as rhEPO in injectable hydrogels. The nanoengineered injectable system was formulated by incorporating two-dimensional layered double hydroxide (LDH) clay materials with a high surface area into alginate hydrogels for sustained delivery. The inclusion of LDH in the hydrogel network not only improved the mechanical properties of the hydrogels (5-30 times that of alginate hydrogel) but also exhibited a high binding affinity to proteins without altering their bioactivity and conformation. Furthermore, the nanoengineered injectable hydrogels (INHs) demonstrated quick gelation, injectability, and excellent adhesion properties on human skin. The in vitro release test of EPO from conventional alginate hydrogels (Alg-Gel) showed 86% EPO release within 108 h while INHs showed greater control over the initial burst and released only 24% of EPO in the same incubation time. INH-based ink was successfully used for 3D printing, resulting in scaffolds with good shape fidelity and stability in cell culture media. Controlled release of EPO from INHs facilitated superior angiogenic potential in ovo (chick chorioallantoic membrane) compared to Alg-Gel. When subcutaneously implanted in albino mice, the INHs formed a stable gel in vivo without inducing any adverse effects. The results suggest that the proposed INHs in this study can be utilized as a minimally invasive injectable platform or as 3D printed patches for the delivery of protein therapeutics to facilitate tissue regeneration.

Stimuli-Responsive Hydrogels for Protein Delivery

Proteins and peptides are potential therapeutic agents, but their physiochemical properties make their use as drug substances challenging. Hydrogels are hydrophilic polymeric networks that can swell and retain high amounts of water or biological fluids without being dissolved. Due to their biocompatibility, their porous structure, which enables the transport of various peptides and proteins, and their protective effect against degradation, hydrogels have gained prominence as ideal carriers for these molecules' delivery. Particularly, stimuli-responsive hydrogels exhibit physicochemical transitions in response to subtle modifications in the surrounding environment, leading to the controlled release of entrapped proteins or peptides. This review is focused on the application of these hydrogels in protein and peptide delivery, including a brief overview of therapeutic proteins and types of stimuli-responsive polymers.

An Update on Strategies to Deliver Protein and Peptide Drugs to the Eye

In the past few decades, advancements in protein engineering, biotechnology, and structural biochemistry have resulted in the discovery of various techniques that enhanced the production yield of proteins, targetability, circulating half-life, product purity, and functionality of proteins and peptides. As a result, the utilization of proteins and peptides has increased in the treatment of many conditions, including ocular diseases. Ocular delivery of large molecules poses several challenges due to their high molecular weight, hydrophilicity, unstable nature, and poor permeation through cellular and enzymatic barriers. The use of novel strategies for delivering protein and peptides such as glycoengineering, PEGylation, Fc-fusion, chitosan nanoparticles, and liposomes have improved the efficacy, safety, and stability, which consequently expanded the therapeutic potential of proteins. This review article highlights various proteins and peptides that are useful in ocular disorders, challenges in their delivery to the eye, and strategies to enhance ocular bioavailability using novel delivery approaches. In addition, a few futuristic approaches that will assist in the ocular delivery of proteins and peptides were also discussed.

Moderate-Affinity Affibodies Modulate the Delivery and Bioactivity of Bone Morphogenetic Protein-2

Uncontrolled bone morphogenetic protein-2 (BMP-2) release can lead to off-target bone growth and other adverse events. To tackle this challenge, yeast surface display is used to identify unique BMP-2-specific protein binders known as affibodies that bind to BMP-2 with different affinities. Biolayer interferometry reveals an equilibrium dissociation constant of 10.7 nm for the interaction between BMP-2 and high-affinity affibody and 34.8 nm for the interaction between BMP-2 and the low-affinity affibody. The low-affinity affibody-BMP-2 interaction also exhibits an off-rate constant that is an order of magnitude higher. Computational modeling of affibody-BMP-2 binding predicts that the high- and low-affinity affibodies bind to two distinct sites on BMP-2 that function as different cell-receptor binding sites. BMP-2 binding to affibodies reduces expression of the osteogenic marker alkaline phosphatase (ALP) in C2C12 myoblasts. Affibody-conjugated polyethylene glycol-maleimide hydrogels increase uptake of BMP-2 compared to affibody-free hydrogels, and high-affinity hydrogels exhibit lower BMP-2 release into serum compared to low-affinity hydrogels and affibody-free hydrogels over four weeks. Loading BMP-2 into affibody-conjugated hydrogels prolongs ALP activity of C2C12 myoblasts compared to soluble BMP-2. This work demonstrates that affibodies with different affinities can modulate BMP-2 delivery and activity, creating a promising approach for controlling BMP-2 delivery in clinical applications.

Applications of Degradable Hydrogels in Novel Approaches to Disease Treatment and New Modes of Drug Delivery

Hydrogels are particularly suitable materials for loading drug delivery agents; their high water content provides a biocompatible environment for most biomolecules, and their cross-linked nature protects the loaded agents from damage. During delivery, the delivered substance usually needs to be released gradually over time, which can be achieved by degradable cross-linked chains. In recent years, biodegradable hydrogels have become a promising technology in new methods of disease treatment and drug delivery methods due to their many advantageous properties. This review briefly discusses the degradation mechanisms of different types of biodegradable hydrogel systems and introduces the specific applications of degradable hydrogels in several new methods of disease treatment and drug delivery methods.

Bioactive Materials for Bone Regeneration: Biomolecules and Delivery Systems

Novel tissue regeneration strategies are constantly being developed worldwide. Research on bone regeneration is noteworthy, as many promising new approaches have been documented with novel strategies currently under investigation. Innovative biomaterials that allow the coordinated and well-controlled repair of bone fractures and bone loss are being designed to reduce the need for autologous or allogeneic bone grafts eventually. The current engineering technologies permit the construction of synthetic, complex, biomimetic biomaterials with properties nearly as good as those of natural bone with good biocompatibility. To ensure that all these requirements meet, bioactive molecules are coupled to structural scaffolding constituents to form a final product with the desired physical, chemical, and biological properties. Bioactive molecules that have been used to promote bone regeneration include protein growth factors, peptides, amino acids, hormones, lipids, and flavonoids. Various strategies have been adapted to investigate the coupling of bioactive molecules with scaffolding materials to sustain activity and allow controlled release. The current manuscript is a thorough survey of the strategies that have been exploited for the delivery of biomolecules for bone regeneration purposes, from choosing the bioactive molecule to selecting the optimal strategy to synthesize the scaffold and assessing the advantages and disadvantages of various delivery strategies.

Thermo-responsive Diels-Alder stabilized hydrogels for ocular drug delivery of a corticosteroid and an anti-VEGF fab fragment

In the present study, a novel in situ forming thermosensitive hydrogel system was investigated as a versatile drug delivery system for ocular therapy. For this purpose, two thermosensitive ABA triblock copolymers bearing either furan or maleimide moieties were synthesized, named respectively poly(NIPAM-co-HEA/Furan)-PEG6K-P(NIPAM-co-HEA/Furan) (PNF) and poly(NIPAM-co-HEA/Maleimide)-PEG6K-P(NIPAM-co-HEA/-Maleimide) (PNM). Hydrogels were obtained upon mixing aqueous PNF and PNM solutions followed by incubation at 37 °C. The hydrogel undergoes an immediate (<1 min) sol-gel transition at 37 °C. In situ hydrogel formation at 37 °C was also observed after intravitreal injection of the formulation into an ex vivo rabbit eye. The hydrogel network formation was due to physical self-assembly of the PNIPAM blocks and a catalyst-free furan-maleimide Diels-Alder (DA) chemical crosslinking in the hydrophobic domains of the polymer network. Rheological studies demonstrated sol-gel transition at 23 °C, and DA crosslinks were formed in time within 60 min by increasing the temperature from 4 to 37 °C. When incubated at 37 °C, these hydrogels were stable for at least one year in phosphate buffer of pH 7.4. However, the gels degraded at basic pH 10 and 11 after 13 and 3 days, respectively, due to hydrolysis of ester bonds in the crosslinks of the hydrogel network. The hydrogel was loaded with an anti-VEGF antibody fragment (FAB; 48.4 kDa) or with corticosteroid dexamethasone (dex) by dissolving (FAB) or dispersing (DEX) in the hydrogel precursor solution. The FAB fragment in unmodified form was quantitatively released over 13 days after an initial burst release of 46, 45 and 28 % of the loading for the 5, 10 and 20 wt% hydrogel, respectively, due to gel dehydration during formation. The low molecular weight drug dexamethasone was almost quantitively released in 35 days. The slower release of dexamethasone compared to the FAB fragment can likely be explained by the solubilization of this hydrophobic drug in the hydrophobic domains of the gel. The thermosensitive gels showed good cytocompatibility when brought in contact with macrophage-like mural cells (RAW 264.7) and human retinal pigment epithelium-derived (ARPE-19) cells. This study demonstrates that PNF-PNM thermogel may be a suitable formulation for sustained release of bioactive agents into the eye for treating posterior segment eye diseases.

Development of a Novel Histatin-5 Mucoadhesive Gel for the Treatment of Oral Mucositis: In Vitro Characterization and In Vivo Evaluation

Antimicrobial peptides have appeared to be promising candidates for therapeutic purposes due to their broad antimicrobial activity and non-toxicity. Histatin-5 (Hst-5) is a notable salivary antimicrobial peptide that exhibited therapeutic properties in the oral cavity. Oral mucositis is an acute inflammation of the oral cavity, following cancer therapy. The current treatment methods of oral mucositis have low effectiveness. The aim of this study was to design, formulate and characterize a mucoadhesive gel delivery system for Hst-5 usage in the treatment of oral mucositis. Carbopol 934 and hydroxypropyl methylcellulose (HPMC) have been used in the development of a Hst-5 mucoadhesive gel that was optimized by using Box-Behnken design. The optimized formulation was evaluated in-vitro, based on mucoadhesive strength, viscoelasticity, spreadability, release rate, peptide secondary structure analysis, antimicrobial activity, and storage stability. The efficacy of Hst-5 gel was assessed in vivo in a chemotherapy-induced mucositis model. The results showed a sustained release of Hst-5 from the new formulation. Hst-5 gel exerted antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans. The histopathological, immunohistochemical and statistical analysis showed that the Hst-5 gel had wound healing activity in vivo. The findings of this study indicate that the mentioned compound possesses promising potential as a novel and efficient therapeutic agent in managing oral mucositis. Moreover, the results suggest that the compound is commercially feasible for further development and utilization.

Hydration-induced Void-containing Hydrogels for Encapsulation and Sustained Release of Small Hydrophilic Molecules

Efficient encapsulation and sustained release of small hydrophilic molecules from traditional hydrogel systems have been challenging due to the large mesh size of 3D networks and high water content. Furthermore, the encapsulated molecules are prone to early release from the hydrogel prior to use, resulting in a short shelf life of the formulation. Here, we present a hydration-induced void-containing hydrogel (HVH) based on hyperbranched polyglycerol-poly(propylene oxide)-hyperbranched polyglycerol (HPG-PPG-HPG) as a robust and efficient delivery system for small hydrophilic molecules. Specifically, after the HPG-PPG-HPG is incubated overnight at 4 °C in the drug solution, it is hydrated into a hydrogel containing micron-sized voids, which could encapsulate hydrophilic drugs and achieve 100% drug encapsulation efficiency. In addition, the voids are surrounded by a densely packed polymer matrix, which restricts drug transport to achieve sustained drug release. The hydrogel/drug formulation can be stored for several months without changing the drug encapsulation and release properties. HVH hydrogels are injectable due to shear thinning properties. In rats, a single injection of the HPG-PPG-HPG hydrogel containing 8 μg of tetrodotoxin (TTX) produced sciatic nerve block lasting up to 10 hours without any TTX-related systemic toxicity nor local toxicity to nerves and muscles.

Strategies for overcoming protein and peptide instability in biodegradable drug delivery systems

The global pharmaceutical market has recently shifted its focus from small molecule drugs to peptide, protein, and nucleic acid drugs, which now comprise a majority of the top-selling pharmaceutical products on the market. Although these biologics often offer improved drug specificity, new mechanisms of action, and/or enhanced efficacy, they also present new challenges, including an increased potential for degradation and a need for frequent administration via more invasive administration routes, which can limit patient access, patient adherence, and ultimately the clinical impact of these drugs. Controlled-release systems have the potential to mitigate these challenges by offering superior control over in vivo drug levels, localizing these drugs to tissues of interest (e.g., tumors), and reducing administration frequency. Unfortunately, adapting controlled-release devices to release biologics has proven difficult due to the poor stability of biologics. In this review, we summarize the current state of controlled-release peptides and proteins, discuss existing techniques used to stabilize these drugs through encapsulation, storage, and in vivo release, and provide perspective on the most promising opportunities for the clinical translation of controlled-release peptides and proteins.

Engineering of a NIR-activable hydrogel-coated mesoporous bioactive glass scaffold with dual-mode parathyroid hormone derivative release property for angiogenesis and bone regeneration

Osteogenesis, osteoclastogenesis, and angiogenesis play crucial roles in bone regeneration. Parathyroid hormone (PTH), an FDA-approved drug with pro-osteogenic, pro-osteoclastogenic and proangiogenic capabilities, has been employed for clinical osteoporosis treatment through systemic intermittent administration. However, the successful application of PTH for local bone defect repair generally requires the incorporation and delivery by appropriate carriers. Though several scaffolds have been developed to deliver PTH, they suffer from the weaknesses such as uncontrollable PTH release, insufficient porous structure and low mechanical strength. Herein, a novel kind of NIR-activable scaffold (CBP/MBGS/PTHrP-2) with dual-mode PTHrP-2 (a PTH derivative) release capability is developed to synergistically promote osteogenesis and angiogenesis for high-efficacy bone regeneration, which is fabricated by integrating the PTHrP-2-loaded hierarchically mesoporous bioactive glass (MBG) into the N-hydroxymethylacrylamide-modified, photothermal agent-doped, poly(N-isopropylacrylamide)-based thermosensitive hydrogels through assembly process. Upon on/off NIR irradiation, the thermoresponsive hydrogel gating undergoes a reversible phase transition to allow the precise control of on-demand pulsatile and long-term slow release of PTHrP-2 from MBG mesopores. Such NIR-activated dual-mode delivery of PTHrP-2 by this scaffold enables a well-maintained PTHrP-2 concentration at the bone defect sites to continually stimulate vascularization and promote osteoblasts to facilitate and accelerate bone remodeling. In vivo experiments confirm the significant improvement of bone reparative effect on critical-size femoral defects of rats. This work paves an avenue for the development of novel dual-mode delivery systems for effective bone regeneration.

An osteoinductive and biodegradable intramedullary implant accelerates bone healing and mitigates complications of bone transport in male rats

Bone transport is a surgery-driven procedure for the treatment of large bone defects. However, challenging complications include prolonged consolidation, docking site nonunion and pin tract infection. Here, we develop an osteoinductive and biodegradable intramedullary implant by a hybrid tissue engineering construct technique to enable sustained delivery of bone morphogenetic protein-2 as an adjunctive therapy. In a male rat bone transport model, the eluting bone morphogenetic protein-2 from the implants accelerates bone formation and remodeling, leading to early bony fusion as shown by imaging, mechanical testing, histological analysis, and microarray assays. Moreover, no pin tract infection but tight osseointegration are observed. In contrast, conventional treatments show higher proportion of docking site nonunion and pin tract infection. The findings of this study demonstrate that the novel intramedullary implant holds great promise for advancing bone transport techniques by promoting bone regeneration and reducing complications in the treatment of bone defects.

Statistical Optimization of Hydrazone-Crosslinked Hyaluronic Acid Hydrogels for Protein Delivery

Hydrazone-crosslinked hydrogels are attractive protein delivery vehicles for regenerative medicine. However, each regenerative medicine application requires unique hydrogel properties to achieve an ideal outcome. The properties of a hydrogel can be impacted by numerous factors involved in its fabrication. We used design of experiments (DoE) statistical modeling to efficiently optimize the physicochemical properties of a hyaluronic acid (HA) hydrazone-crosslinked hydrogel for protein delivery for bone regeneration. We modified HA with either adipic acid dihydrazide (HA-ADH) or aldehyde (HA-Ox) functional groups and used DoE to evaluate the interactions of three input variables, the molecular weight of HA (40 or 100 kDa), the concentration of HA-ADH (1-3% w/v), and the concentration of HA-Ox (1-3% w/v), on three output responses, gelation time, compressive modulus, and hydrogel stability over time. We identified 100 kDa HA-ADH3.0HA-Ox2.33 as an optimal hydrogel that met all of our design criteria, including displaying a gelation time of 3.7 minutes, compressive modulus of 62.1 Pa, and minimal mass change over 28 days. For protein delivery, we conjugated affinity proteins called affibodies that were specific to the osteogenic protein bone morphogenetic protein-2 (BMP-2) to HA hydrogels and demonstrated that our platform could control the release of BMP-2 over 28 days. Ultimately, our approach demonstrates the utility of DoE for optimizing hydrazone-crosslinked HA hydrogels for protein delivery.

Glucose-Responsive Microgel Comprising Conventional Insulin and Curcumin-Laden Nanoparticles: a Potential Combination for Diabetes Management

Successful management of type 2 diabetes mellitus (T2DM), a complex and chronic disease, requires a combination of anti-hyperglycemic and anti-inflammatory agents. Here, we have conceptualized and tested an integrated "closed-loop mimic" in the form of a glucose-responsive microgel (GRM) based on chitosan, comprising conventional insulin (INS) and curcumin-laden nanoparticles (nCUR) as a potential strategy for effective management of the disease. In addition to mimicking the normal, on-demand INS secretion, such delivery systems display an uninterrupted release of nCUR to combat the inflammation, oxidative stress, lipid metabolic abnormality, and endothelial dysfunction components of T2DM. Additives such as gum arabic (GA) led to a fivefold increased INS loading capacity compared to GRM without GA. The GRMs showed excellent in vitro on-demand INS release, while a constant nCUR release is observed irrespective of glucose concentrations. Thus, this study demonstrates a promising drug delivery technology that can simultaneously, and at physiological/pathophysiological relevance, deliver two drugs of distinct physicochemical attributes in the same formulation.

Hydrogel-Based Biosensors for Effective Therapeutics

Nanotechnology and polymer engineering are navigating toward new developments to control and overcome complex problems. In the last few decades, polymer engineering has received researchers' attention and similarly, polymeric network-engineered structures have been vastly studied. Prior to therapeutic application, early and rapid detection analyses are critical. Therefore, developing hydrogel-based sensors to manage the acute expression of diseases and malignancies to devise therapeutic approaches demands advanced nanoengineering. However, nano-therapeutics have emerged as an alternative approach to tackling strenuous diseases. Similarly, sensing applications for multiple kinds of analytes in water-based environments and other media are gaining wide interest. It has also been observed that these functional roles can be used as alternative approaches to the detection of a wide range of biomolecules and pathogenic proteins. Moreover, hydrogels have emerged as a three-dimensional (3D) polymeric network that consists of hydrophilic natural or synthetic polymers with multidimensional dynamics. The resemblance of hydrogels to tissue structure makes them more unique to study inquisitively. Preceding studies have shown a vast spectrum of synthetic and natural polymer applications in the field of biotechnology and molecular diagnostics. This review explores recent studies on synthetic and natural polymers engineered hydrogel-based biosensors and their applications in multipurpose diagnostics and therapeutics. We review the latest studies on hydrogel-engineered biosensors, exclusively DNA-based and DNA hydrogel-fabricated biosensors.

Innovative Strategies for Drug Delivery to the Ocular Posterior Segment

Innovative and new drug delivery systems (DDSs) have recently been developed to vehicle treatments and drugs to the ocular posterior segment and the retina. New formulations and technological developments, such as nanotechnology, novel matrices, and non-traditional treatment strategies, open new perspectives in this field. The aim of this mini-review is to highlight promising strategies reported in the current literature based on innovative routes to overcome the anatomical and physiological barriers of the vitreoretinal structures. The paper also describes the challenges in finding appropriate and pertinent treatments that provide safety and efficacy and the problems related to patient compliance, acceptability, effectiveness, and sustained drug delivery. The clinical application of these experimental approaches can help pave the way for standardizing the use of DDSs in developing enhanced treatment strategies and personalized therapeutic options for ocular pathologies.

Template-Based Porous Hydrogel Microparticles as Carriers for Therapeutic Proteins

Hydrogels have been extensively researched for over 60 years for their limitless applications in biomedical research. In this study, porous hydrogel microparticles (PHMPs) made of poly(ethylene glycol) diacrylamide were investigated for their potential as a delivery platform for therapeutic proteins. These particles are made using hard calcium carbonate (CaCO₃) templates, which can easily be dissolved under acidic conditions. After optimization of the synthesis processes, both CaCO₃ templates and PHMPs were characterized using a wide range of techniques. Then, using an array of proteins with different physicochemical properties, the encapsulation efficiency of proteins in PHMPs was evaluated under different conditions. Strategies to enhance protein encapsulation via modulation of particle surface charge to increase electrostatic interactions and conjugation using EDC/NHS chemistry were also investigated. Conjugation of bovine serum albumin to PHMPs showed increased encapsulation and diminished release over time, highlighting the potential of PHMPs as a versatile delivery platform for therapeutic proteins such as enzymes or antibodies.

Delivery Systems in Ocular Retinopathies: The Promising Future of Intravitreal Hydrogels as Sustained-Release Scaffolds

Slow-release delivery systems are needed to ensure long-term sustained treatments for retinal diseases such as age-related macular degeneration and diabetic retinopathy, which are currently treated with anti-angiogenic agents that require frequent intraocular injections. These can cause serious co-morbidities for the patients and are far from providing the adequate drug/protein release rates and required pharmacokinetics to sustain prolonged efficacy. This review focuses on the use of hydrogels, particularly on temperature-responsive hydrogels as delivery vehicles for the intravitreal injection of retinal therapies, their advantages and disadvantages for intraocular administration, and the current advances in their use to treat retinal diseases.

Design and Application of Hybrid Polymer-Protein Systems in Cancer Therapy

Polymer-protein systems have excellent characteristics, such as non-toxic, non-irritating, good water solubility and biocompatibility, which makes them very appealing as cancer therapeutics agents. Inspiringly, they can achieve sustained release and targeted delivery of drugs, greatly improving the effect of cancer therapy and reducing side effects. However, many challenges, such as reducing the toxicity of materials, protecting the activities of proteins and controlling the release of proteins, still need to be overcome. In this review, the design of hybrid polymer-protein systems, including the selection of polymers and the bonding forms of polymer-protein systems, is presented. Meanwhile, vital considerations, including reaction conditions and the release of proteins in the design process, are addressed. Then, hybrid polymer-protein systems developed in the past decades for cancer therapy, including targeted therapy, gene therapy, phototherapy, immunotherapy and vaccine therapy, are summarized. Furthermore, challenges for the hybrid polymer-protein systems in cancer therapy are exemplified, and the perspectives of the field are covered.

Amphiphilic Polypeptides Obtained by Post-Polymerization Modification of Poly-l-Lysine as Systems for Combined Delivery of Paclitaxel and siRNA

The development of effective anti-cancer therapeutics remains one of the current pharmaceutical challenges. The joint delivery of chemotherapeutic agents and biopharmaceuticals is a cutting-edge approach to creating therapeutic agents of enhanced efficacy. In this study, amphiphilic polypeptide delivery systems capable of loading both hydrophobic drug and small interfering RNA (siRNA) were developed. The synthesis of amphiphilic polypeptides included two steps: (i) synthesis of poly-αl-lysine by ring-opening polymerization and (ii) its post-polymerization modification with hydrophobic l-amino acid and l-arginine/l-histidine. The obtained polymers were used for the preparation of single and dual delivery systems of PTX and short double-stranded nucleic acid. The obtained double component systems were quite compact and had a hydrodynamic diameter in the range of 90-200 nm depending on the polypeptide. The release of PTX from the formulations was studied, and the release profiles were approximated using a number of mathematical dissolution models to establish the most probable release mechanism. A determination of the cytotoxicity in normal (HEK 293T) and cancer (HeLa and A549) cells revealed the higher toxicity of the polypeptide particles to cancer cells. The separate evaluation of the biological activity of PTX and anti-GFP siRNA formulations testified the inhibitory efficiency of PTX formulations based on all polypeptides (IC₅₀ 4.5-6.2 ng/mL), while gene silencing was effective only for the Tyr-Arg-containing polypeptide (56-70% GFP knockdown).

Injectable hydrogel imbibed with camptothecin-loaded mesoporous silica nanoparticles as an implantable sustained delivery depot for cancer therapy

In recent years, injectable stimuli-sensitive hydrogels are employed as suitable drug delivery carriers for the release of various anti-cancer drugs. However, large pore size of the microporous hydrogel trigger release of small molecular anticancer drug that limits hydrogel application in cancer therapy. Therefore, introducing reinforcing fillers such as mesoporous silica nanoparticles (MSNs) can not only load different type of anticancer drugs but also prevent the premature release of drugs due to the strengthening of the networks. Furthermore, high specific surface area, suitable size, large pore volume, and stable physicochemical properties of MSNs can improve the therapeutic efficacy. In this study, to sustain the release of hydrophobic anticancer drug, camptothecin (CPT) was loaded into MSNs, and then imbibed into the physiological stimuli-sensitive poly(ethylene glycol)-poly(β-aminoester urethane) (PAEU) hydrogels. MSN-imbibed PAEU hydrogels exhibited prolonged release of CPT than MSNs and PAEU hydrogel alone. Furthermore, MSN-imbibed PAEU copolymers form stable viscoelastic gel depot into the subcutaneous layers of Sprague-Dawley rats and found to be safe and not induced toxicity to healthy organs, implying biodegradability and safety of the hydrogels. Interestingly, CPT-loaded hydrogels shown dose-dependent toxicity to A549 and B16F10 cells. These results demonstrated that MSN-imbibed PAEU hydrogel with biocompatible, biodegradable, and in situ gel forming property could be a useful drug delivery depot for sustained release of anticancer drugs.

Thermo-pH-Sensitive Polymer Conjugated Glucose Oxidase for Tumor-Selective Starvation-Oxidation-Immune Therapy

Protein drugs are increasingly used as therapeutics for the treatment of cancer. However, their inherent drawbacks, such as poor stability, low cell membrane and tissue permeability, lack of tumor selectivity, and severe side effects, limit their wide applications in cancer therapy. Herein, screening of a thermo-pH-sensitive polymer-glucose oxidase conjugate that can controllably self-assemble into nanoparticles with improved stability is reported. The size, surface charge, and bioactivity of the conjugate can be tuned by adjustment of the solution temperature and pH. The cellular uptake, intracellular hydrogen peroxide generation, and tumor cell spheroid penetration of the conjugate are greatly enhanced under the acidic tumor microenvironment, leading to increased cytotoxicity to tumor cells. Upon a single intratumoural injection, the conjugate penetrates into the whole tumor tissue but hardly diffuses into the normal tissues, resulting in the eradication of the tumors in mice without perceivable side effects. Simultaneously, the conjugate induces a robust antitumor immunity to efficiently inhibit the growth of distant tumors, especially in combination with an immune checkpoint inhibitor. These findings provide a novel and general strategy to make multifunctional protein-polymer conjugates with responsiveness to the acidic tumor microenvironment for selective tumor therapy.

Polymerization in living organisms

Vital biomacromolecules, such as RNA, DNA, polysaccharides and proteins, are synthesized inside cells via the polymerization of small biomolecules to support and multiply life. The study of polymerization reactions in living organisms is an emerging field in which the high diversity and efficiency of chemistry as well as the flexibility and ingeniousness of physiological environment are incisively and vividly embodied. Efforts have been made to design and develop in situ intra/extracellular polymerization reactions. Many important research areas, including cell surface engineering, biocompatible polymerization, cell behavior regulation, living cell imaging, targeted bacteriostasis and precise tumor therapy, have witnessed the elegant demeanour of polymerization reactions in living organisms. In this review, recent advances in polymerization in living organisms are summarized and presented according to different polymerization methods. The inspiration from biomacromolecule synthesis in nature highlights the feasibility and uniqueness of triggering living polymerization for cell-based biological applications. A series of examples of polymerization reactions in living organisms are discussed, along with their designs, mechanisms of action, and corresponding applications. The current challenges and prospects in this lifeful field are also proposed.

The development of a solid lipid nanoparticle (SLN)-based lacticin 3147 hydrogel for the treatment of wound infections

Chronic wounds affect millions of people globally. This number is set to rise with the increasing incidence of antimicrobial-resistant bacterial infections, such as methicillin-resistant Staphylococcus aureus (MRSA), which impair the healing of chronic wounds. Lacticin 3147 is a two-peptide chain bacteriocin produced by Lactococcus lactis that is active against S. aureus including MRSA strains. Previously, poor physicochemical properties of the peptides were overcome by the encapsulation of lacticin 3147 into solid lipid nanoparticles. Here, a lacticin 3147 solid lipid nanoparticle gel is proposed as a topical treatment for S. aureus and MRSA wound infections. Initially, lacticin 3147's antimicrobial activity against S. aureus was determined before encapsulation into solid lipid nanoparticles. An optimised gel formulation with the desired physicochemical properties for topical application was developed, and the lacticin-loaded solid lipid nanoparticles and free lacticin 3147 aqueous solution were incorporated into separate gels. The release of lacticin 3147 from both the solid lipid nanoparticle and free lacticin gels was measured where the solid lipid nanoparticle gel exhibited increased activity for a longer period (11 days) compared to the free lacticin gel (9 days). Both gels displayed potent activity ex vivo against S. aureus-infected pig skin with significant bacterial eradication (> 75%) after 1 h. Thus, a long-acting potent lacticin 3147 solid lipid nanoparticle gel with the required physicochemical properties for topical delivery of lacticin 3147 to the skin for the potential treatment of S. aureus-infected chronic wounds was developed.

Dynamic Covalent Dextran Hydrogels as Injectable, Self-Adjuvating Peptide Vaccine Depots

Dextran-based hydrogels are promising therapeutic materials for drug delivery, tissue regeneration devices, and cell therapy vectors, due to their high biocompatibility, along with their ability to protect and release active therapeutic agents. This report describes the synthesis, characterization, and application of a new dynamic covalent dextran hydrogel as an injectable depot for peptide vaccines. Dynamic covalent crosslinks based on double Michael addition of thiols to alkynones impart the dextran hydrogel with shear-thinning and self-healing capabilities, enabling hydrogel injection. These injectable, non-toxic hydrogels show adjuvant potential and have predictable sub-millimolar loading and release of the peptide antigen SIINFEKL, which after its release is able to activate T-cells, demonstrating that the hydrogels deliver peptides without modifying their immunogenicity. This work demonstrates the potential of dynamic covalent dextran hydrogels as a sustained-release material for the delivery of peptide vaccines.