Bioinspired supramolecular nanofiber hydrogel through self-assembly of biphenyl-tripeptide for tissue engineering

Advanced applications of smart electrospun nanofibers in cancer therapy: With insight into material capabilities and electrospinning parameters

Cancer remains a major global health challenge, and despite available treatments, its prognosis remains poor. Recently, researchers have turned their attention to intelligent nanofibers for cancer drug delivery. These nanofibers exhibit remarkable capabilities in targeted and controlled drug release. Their inherent characteristics, such as a high surface area-to-volume ratio, make them attractive candidates for drug delivery applications. Smart nanofibers can release drugs in response to specific stimuli, including pH, temperature, magnetic fields, and light. This unique feature not only reduces side effects but also enhances the overall efficiency of drug delivery systems. Electrospinning, a widely used method, allows the precision fabrication of smart nanofibers. Its advantages include high efficiency, user-friendliness, and the ability to control various manufacturing parameters. In this review, we explore the latest developments in producing smart electrospun nanofibers for cancer treatment. Additionally, we discuss the materials used in manufacturing these nanofibers and the critical parameters involved in the electrospinning process.

Mechanical Regulation of Polymer Gels

The mechanical properties of polymer gels devote to emerging devices and machines in fields such as biomedical engineering, flexible bioelectronics, biomimetic actuators, and energy harvesters. Coupling network architectures and interactions has been explored to regulate supportive mechanical characteristics of polymer gels; however, systematic reviews correlating mechanics to interaction forces at the molecular and structural levels remain absent in the field. This review highlights the molecular engineering and structural engineering of polymer gel mechanics and a comprehensive mechanistic understanding of mechanical regulation. Molecular engineering alters molecular architecture and manipulates functional groups/moieties at the molecular level, introducing various interactions and permanent or reversible dynamic bonds as the dissipative energy. Molecular engineering usually uses monomers, cross-linkers, chains, and other additives. Structural engineering utilizes casting methods, solvent phase regulation, mechanochemistry, macromolecule chemical reactions, and biomanufacturing technology to construct and tailor the topological network structures, or heterogeneous modulus compositions. We envision that the perfect combination of molecular and structural engineering may provide a fresh view to extend exciting new perspectives of this burgeoning field. This review also summarizes recent representative applications of polymer gels with excellent mechanical properties. Conclusions and perspectives are also provided from five aspects of concise summary, mechanical mechanism, biofabrication methods, upgraded applications, and synergistic methodology.

Harnessing Peptide-Based Hydrogels for Enhanced Cartilage Tissue Engineering

Cartilage tissue engineering remains a formidable challenge due to its complex, avascular structure and limited regenerative capacity. Traditional approaches, such as microfracture, autografts, and stem cell delivery, often fail to restore functional tissue adequately. Recently, there has been a surge in the exploration of new materials that mimic the extracellular microenvironment necessary to guide tissue regeneration. This review investigates the potential of peptide-based hydrogels as an innovative solution for cartilage regeneration. These hydrogels, formed via supramolecular self-assembly, exhibit excellent properties, including biocompatibility, ECM mimicry, and controlled biodegradation, making them highly suitable for cartilage tissue engineering. This review explains the structure of cartilage and the principles of supramolecular and peptide hydrogels. It also delves into their specific properties relevant to cartilage regeneration. Additionally, this review presents recent examples and a comparative analysis of various peptide-based hydrogels used for cartilage regeneration. The review also addresses the translational challenges of these materials, highlighting regulatory hurdles and the complexities of clinical application. This comprehensive investigation provides valuable insights for biomedical researchers, tissue engineers, and clinical professionals aiming to enhance cartilage repair methodologies.

Stimuli-responsive peptide assemblies: Design, self-assembly, modulation, and biomedical applications

Peptide molecules have design flexibility, self-assembly ability, high biocompatibility, good biodegradability, and easy functionalization, which promote their applications as versatile biomaterials for tissue engineering and biomedicine. In addition, the functionalization of self-assembled peptide nanomaterials with other additive components enhances their stimuli-responsive functions, promoting function-specific applications that induced by both internal and external stimulations. In this review, we demonstrate recent advance in the peptide molecular design, self-assembly, functional tailoring, and biomedical applications of peptide-based nanomaterials. The strategies on the design and synthesis of single, dual, and multiple stimuli-responsive peptide-based nanomaterials with various dimensions are analyzed, and the functional regulation of peptide nanomaterials with active components such as metal/metal oxide, DNA/RNA, polysaccharides, photosensitizers, 2D materials, and others are discussed. In addition, the designed peptide-based nanomaterials with temperature-, pH-, ion-, light-, enzyme-, and ROS-responsive abilities for drug delivery, bioimaging, cancer therapy, gene therapy, antibacterial, as well as wound healing and dressing applications are presented and discussed. This comprehensive review provides detailed methodologies and advanced techniques on the synthesis of peptide nanomaterials from molecular biology, materials science, and nanotechnology, which will guide and inspire the molecular level design of peptides with specific and multiple functions for function-specific applications.

Photonic control of ligand nanospacing in self-assembly regulates stem cell fate

Extracellular matrix (ECM) undergoes dynamic inflation that dynamically changes ligand nanospacing but has not been explored. Here we utilize ECM-mimicking photocontrolled supramolecular ligand-tunable Azo+ self-assembly composed of azobenzene derivatives (Azo+) stacked via cation-π interactions and stabilized with RGD ligand-bearing poly(acrylic acid). Near-infrared-upconverted-ultraviolet light induces cis-Azo+-mediated inflation that suppresses cation-π interactions, thereby inflating liganded self-assembly. This inflation increases nanospacing of "closely nanospaced" ligands from 1.8 nm to 2.6 nm and the surface area of liganded self-assembly that facilitate stem cell adhesion, mechanosensing, and differentiation both in vitro and in vivo, including the release of loaded molecules by destabilizing water bridges and hydrogen bonds between the Azo+ molecules and loaded molecules. Conversely, visible light induces trans-Azo+ formation that facilitates cation-π interactions, thereby deflating self-assembly with "closely nanospaced" ligands that inhibits stem cell adhesion, mechanosensing, and differentiation. In stark contrast, when ligand nanospacing increases from 8.7 nm to 12.2 nm via the inflation of self-assembly, the surface area of "distantly nanospaced" ligands increases, thereby suppressing stem cell adhesion, mechanosensing, and differentiation. Long-term in vivo stability of self-assembly via real-time tracking and upconversion are verified. This tuning of ligand nanospacing can unravel dynamic ligand-cell interactions for stem cell-regulated tissue regeneration.

Advancements and Challenges in Hydrogel Engineering for Regenerative Medicine

This manuscript covers the latest advancements and persisting challenges in the domain of tissue engineering, with a focus on the development and engineering of hydrogel scaffolds. It highlights the critical role of these scaffolds in emulating the native tissue environment, thereby providing a supportive matrix for cell growth, tissue integration, and reducing adverse reactions. Despite significant progress, this manuscript emphasizes the ongoing struggle to achieve an optimal balance between biocompatibility, biodegradability, and mechanical stability, crucial for clinical success. It also explores the integration of cutting-edge technologies like 3D bioprinting and biofabrication in constructing complex tissue structures, alongside innovative materials and techniques aimed at enhancing tissue growth and functionality. Through a detailed examination of these efforts, the manuscript sheds light on the potential of hydrogels in advancing regenerative medicine and the necessity for multidisciplinary collaboration to navigate the challenges ahead.

Molecular co-assembled strategy tuning protein conformation for cartilage regeneration

The assembly of oligopeptide and polypeptide molecules can reconstruct various ordered advanced structures through intermolecular interactions to achieve protein-like biofunction. Here, we develop a "molecular velcro"-inspired peptide and gelatin co-assembly strategy, in which amphiphilic supramolecular tripeptides are attached to the molecular chain of gelatin methacryloyl via intra-/intermolecular interactions. We perform molecular docking and dynamics simulations to demonstrate the feasibility of this strategy and reveal the advanced structural transition of the co-assembled hydrogel, which brings more ordered β-sheet content and 10-fold or more compressive strength improvement. We conduct transcriptome analysis to reveal the role of co-assembled hydrogel in promoting cell proliferation and chondrogenic differentiation. Subcutaneous implantation evaluation confirms considerably reduced inflammatory responses and immunogenicity in comparison with type I collagen. We demonstrate that bone mesenchymal stem cells-laden co-assembled hydrogel can be stably fixed in rabbit knee joint defects by photocuring, which significantly facilitates hyaline cartilage regeneration after three months. This co-assembly strategy provides an approach for developing cartilage regenerative biomaterials.

Magnetic nanoparticles for ferroptosis cancer therapy with diagnostic imaging

Ferroptosis offers a novel method for overcoming therapeutic resistance of cancers to conventional cancer treatment regimens. Its effective use as a cancer therapy requires a precisely targeted approach, which can be facilitated by using nanoparticles and nanomedicine, and their use to enhance ferroptosis is indeed a growing area of research. While a few review papers have been published on iron-dependent mechanism and inducers of ferroptosis cancer therapy that partly covers ferroptosis nanoparticles, there is a need for a comprehensive review focusing on the design of magnetic nanoparticles that can typically supply iron ions to promote ferroptosis and simultaneously enable targeted ferroptosis cancer nanomedicine. Furthermore, magnetic nanoparticles can locally induce ferroptosis and combinational ferroptosis with diagnostic magnetic resonance imaging (MRI). The use of remotely controllable magnetic nanocarriers can offer highly effective localized image-guided ferroptosis cancer nanomedicine. Here, recent developments in magnetically manipulable nanocarriers for ferroptosis cancer nanomedicine with medical imaging are summarized. This review also highlights the advantages of current state-of-the-art image-guided ferroptosis cancer nanomedicine. Finally, image guided combinational ferroptosis cancer therapy with conventional apoptosis-based therapy that enables synergistic tumor therapy is discussed for clinical translations.

Recent advances in photo-crosslinkable methacrylated silk (Sil-MA)-based scaffolds for regenerative medicine: A review

Silks fibroin can be chemically modified through amino acid side chains to obtain methacrylated silk (Sil-MA). Sil-MA could be processed into a variety of scaffold forms and combine synergistically with other biomaterials to form composites vehicle. The advent of Sil-MA material has enabled impressive progress in the development of various scaffolds based on Sil-MA type to imitate the structural and functional characteristics of natural tissues. This review highlights the reasonable design and bio-fabrication strategies of diverse Sil-MA-based tissue constructs for regenerative medicine. First, we elucidate modification methodology and characteristics of Sil-MA. Next, we describe characteristics of Sil-MA hydrogels, and focus on the design approaches and formation of different types of Sil-MA-based hydrogels. Thereafter, we present an overview of the recent advances in the application of Sil-MA based scaffolds for regenerative medicine, including detailed strategies for the engineering methods and materials used. Finally, we summarize the current research progress and future directions of Sil-MA in regenerative medicine. This review not only delineates the representative design strategies and their application in regenerative medicine, but also provides new direction in the fabrication of biomaterial constructs for the clinical translation in order to stimulate the future development of implants.

Development of a novel thermogelling PEC-based ECM mimicking nanocomposite bioink for bone tissue engineering

Non-union of large bone defects has been an existing clinical problem. 3D extrusion-based bioprinting provides an efficient approach to tackle such problems. This approach enables the use of various biomaterials, cell types and growth factors in developing a superior bone graft that is specific to the defect. In this article, we have designed and printed an ECM mimicking, self-assembled polyelectrolyte complex (PEC) based fibrous bioink using natural polymers like chitosan-polygalacturonic acid (PGA) and other biomaterials - gelatin, laponite and nanohydroxyapatite with a modified 3D printer. The developed bioink possesses a thermo-reversible sol-gel transition at physiological pH and temperature. Here, we demonstrated that post-printing, our fiber-reinforced bioink had significant cell proliferation with cell viability of >80% and negligible cell morbidity. The practicability of developing this self-assembled PEC-based bioink was assessed. Bioink with 4% gelatin (PECHLG4) had optimal printability with a minimal swelling ratio of approximately 3%. The printed scaffold had integrity for a period of 8 days under 0.5 mg/mL lysozyme concentration. We also evaluated the mechanical property of the bioink using compression analysis which gave an elastic modulus of 16 KPa. This combination of natural polymers and nanocomposite, along with a fibrous network of PECs, is itself a novel approach for 3D bioprinting and can be a preliminary proposition for the treatment of large bone defects.

Constructing ROS-Responsive Supramolecular Gel with Innate Antibacterial Properties

Bacterial infections, especially antibiotic-resistant bacterial infections, pose a significant threat to human health. Supramolecular gel with innate antibacterial properties is an advanced material for the treatment of bacterial infections, which have attracted great attention. Herein, a reactive oxygen species (ROS)-responsive innate antibacterial supramolecular gel is developed by a bottom-up approach based on phenylalanine and hydrazide with innate antibacterial properties. The structure of gelators and intermediate products was characterized by proton nuclear magnetic resonance (1H NMR) and a high-resolution mass spectrum (HRMS). The results of 1H NMR and the Fourier transform infrared spectrum (FT-IR) experiment disclosed that hydrogen bonding and the π-π stacking force are the important self-assembly driving forces of gelators. The microstructure and mechanical properties of gel were studied by Scanning electron microscope (SEM) and Rheometer, respectively. An in vitro degradation experiment proved that the gelator has ROS-responsive degradation properties. The in vitro drug release experiment further manifested that antibiotic-loaded gel has ROS-responsive drug-release performances. An in vitro cytotoxicity experiment showed that the supramolecular gel has good biocompatibility and could promote cell proliferation. The in vitro antibacterial experiment proved that the supramolecular gel has excellent inherent antibacterial properties, and the antibacterial rate against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was 98.6% and 99.1%, respectively. The ROS-responsive supramolecular gel as a novel antibacterial agent has great application prospects in treating antibiotic-resistant bacterial-infected wounds and preventing the development of bacterial resistance.

Customizable Low-Friction Tough Hydrogels for Potential Cartilage Tissue Engineering by a Rapid Orthogonal Photoreactive 3D-Printing Design

Hydrogels have demonstrated wide applications in tissue engineering, but it is still challenging to develop strong, customizable, low-friction artificial scaffolds. Here, we report a rapid orthogonal photoreactive 3D-printing (ROP3P) strategy to achieve the design of high-performance hydrogels in tens of minutes. The orthogonal ruthenium chemistry enables the formation of multinetworks in hydrogels via phenol-coupling reaction and traditional radical polymerization. Further Ca²⁺-cross-linking treatment greatly improves their mechanical properties (6.4 MPa at a critical strain of 300%) and toughness (10.85 MJ m^-3). The tribological investigation reveals that the high elastic moduli of the as-prepared hydrogels improve their lubrication (∼0.02) and wear-resistance performances. These hydrogels are biocompatible and nontoxic and promote bone marrow mesenchymal stem cell adhesion and propagation. The introduction of 1-hydroxy-3-(acryloylamino)-1,1-propanediylbisphosphonic acid units can greatly enhance their antibacterial property to kill typical Escherichia coli and Staphylococcus aureus. Moreover, the rapid ROP3P can achieve hydrogel preparation in several seconds and is readily compatible with making artificial meniscus scaffolds. The printed meniscus-like materials are mechanically stable and can maintain their shape under long-term gliding tests. It is anticipated that these high-performance customizable low-friction tough hydrogels and the highly efficient ROP3P strategy could promote further development and practical applications of hydrogels in biomimetic tissue engineering, materials chemistry, bioelectronics, and so on.

Designed peptide amphiphiles as scaffolds for tissue engineering

Peptide amphiphiles (PAs) are peptide-based molecules that contain a peptide sequence as a head group covalently conjugated to a hydrophobic segment, such as lipid tails. They can self-assemble into well-ordered supramolecular nanostructures such as micelles, vesicles, twisted ribbons and nanofibers. In addition, the diversity of natural amino acids gives the possibility to produce PAs with different sequences. These properties along with their biocompatibility, biodegradability and a high resemblance to native extracellular matrix (ECM) have resulted in PAs being considered as ideal scaffold materials for tissue engineering (TE) applications. This review introduces the 20 natural canonical amino acids as building blocks followed by highlighting the three categories of PAs: amphiphilic peptides, lipidated peptide amphiphiles and supramolecular peptide amphiphile conjugates, as well as their design rules that dictate the peptide self-assembly process. Furthermore, 3D bio-fabrication strategies of PAs hydrogels are discussed and the recent advances of PA-based scaffolds in TE with the emphasis on bone, cartilage and neural tissue regeneration both in vitro and in vivo are considered. Finally, future prospects and challenges are discussed.

Nanofibrous polypeptide hydrogels with collagen-like structure as biomimetic extracellular matrix

Supramolecular peptides exhibit obvious similarities with collagen fibers in terms of self-assembly characteristics, nanofibrous structure, and responsiveness to external stimuli. Here, a series of supramolecular peptides were developed by altering the amino acid sequence, enabling the self-assembly of three types of 4-biphenylacetic acid (BPAA)-tripeptides into fibrous hydrogel through hydrogen bonding and π–π stacking under the influence of ion induction. Transmission electron and scanning electron microscopies revealed that the diameter of the fiber within nanofibrous hydrogels was ~ 10 and ~ 40 nm, respectively, which was similar with the self-assembled collagen fibers. For this reason, these hydrogels could be considered as a biomimetic extracellular substitute. Meanwhile, the gelation concentration induced by ions was even lower than 0.66 wt%, with an elastic modulus of ~ 0.27 kPa, corresponding to a water content of 99.34 wt%. In addition, the three supramolecular hydrogels were found to be good substrates for L929 cell adhesion and MC-3T3 cell proliferation. The overall results implied that BPAA-based hydrogels have a lucrative application potential as cell carriers.

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Tailoring micro/nano-fibers for biomedical applications

Nano/micro fibers have evoked much attention of scientists and have been researched as cutting edge and hotspot in the area of fiber science in recent years due to the rapid development of various advanced manufacturing technologies, and the appearance of fascinating and special functions and properties, such as the enhanced mechanical strength, high surface area to volume ratio and special functionalities shown in the surface, triggered by the nano or micro-scale dimensions. In addition, these outstanding and special characteristics of the nano/micro fibers impart fiber-based materials with wide applications, such as environmental engineering, electronic and biomedical fields. This review mainly focuses on the recent development in the various nano/micro fibers fabrication strategies and corresponding applications in the biomedical fields, including tissue engineering scaffolds, drug delivery, wound healing, and biosensors. Moreover, the challenges for the fabrications and applications and future perspectives are presented.

Advanced application of collagen-based biomaterials in tissue repair and restoration

In tissue engineering, bioactive materials play an important role, providing structural support, cell regulation and establishing a suitable microenvironment to promote tissue regeneration. As the main component of extracellular matrix, collagen is an important natural bioactive material and it has been widely used in scientific research and clinical applications. Collagen is available from a wide range of animal origin, it can be produced by synthesis or through recombinant protein production systems. The use of pure collagen has inherent disadvantages in terms of physico-chemical properties. For this reason, a processed collagen in different ways can better match the specific requirements as biomaterial for tissue repair. Here, collagen may be used in bone/cartilage regeneration, skin regeneration, cardiovascular repair and other fields, by following different processing methods, including cross-linked collagen, complex, structured collagen, mineralized collagen, carrier and other forms, promoting the development of tissue engineering. This review summarizes a wide range of applications of collagen-based biomaterials and their recent progress in several tissue regeneration fields. Furthermore, the application prospect of bioactive materials based on collagen was outlooked, aiming at inspiring more new progress and advancements in tissue engineering research.

Graphical Abstract

Short Peptide-Based Smart Thixotropic Hydrogels †

Thixotropy is a fascinating feature present in many gel systems that has garnered a lot of attention in the medical field in recent decades. When shear stress is applied, the gel transforms into sol and immediately returns to its original state when resting. The thixotropic nature of the hydrogel has inspired scientists to entrap and release enzymes, therapeutics, and other substances inside the human body, where the gel acts as a drug reservoir and can sustainably release therapeutics. Furthermore, thixotropic hydrogels have been widely used in various therapeutic applications, including drug delivery, cornea regeneration and osteogenesis, to name a few. Because of their inherent biocompatibility and structural diversity, peptides are at the forefront of cutting-edge research in this context. This review will discuss the rational design and self-assembly of peptide-based thixotropic hydrogels with some representative examples, followed by their biomedical applications.

Molecular Dynamics-Assisted Design of High Temperature-Resistant Polyacrylamide/Poloxamer Interpenetrating Network Hydrogels

Polyacrylamide has promising applications in a wide variety of fields. However, conventional polyacrylamide is prone to hydrolysis and thermal degradation under high temperature conditions, resulting in a decrease in solution viscosity with increasing temperature, which limits its practical effect. Herein, combining molecular dynamics and practical experiments, we explored a facile and fast mixing strategy to enhance the thermal stability of polyacrylamide by adding common poloxamers to form the interpenetrating network hydrogel. The blending model of three synthetic polyacrylamides (cationic, anionic, and nonionic) and poloxamers was first established, and then the interaction process between them was simulated by all-atom molecular dynamics. In the results, it was found that the hydrogen bonding between the amide groups on all polymers and the oxygen-containing groups (ether and hydroxyl groups) on poloxamers is very strong, which may be the key to improve the high temperature resistance of the hydrogel. Subsequent rheological tests also showed that poloxamers can indeed significantly improve the stability and viscosity of nonionic polyacrylamide containing only amide groups at high temperatures and can maintain a high viscosity of 3550 mPa·S at 80 °C. Transmission electron microscopy further showed that the nonionic polyacrylamide/poloxamer mixture further formed an interpenetrating network structure. In addition, the Fourier transform infrared test also proved the existence of strong hydrogen bonding between the two polymers. This work provides a useful idea for improving the properties of polyacrylamide, especially for the design of high temperature materials for physical blending.

An Overview of the Supramolecular Systems for Gene and Drug Delivery in Tissue Regeneration

Tissue regeneration is a prominent area of research, developing biomaterials aimed to be tunable, mechanistic scaffolds that mimic the physiological environment of the tissue. These biomaterials are projected to effectively possess similar chemical and biological properties, while at the same time are required to be safely and quickly degradable in the body once the desired restoration is achieved. Supramolecular systems composed of reversible, non-covalently connected, self-assembly units that respond to biological stimuli and signal cells have efficiently been developed as preferred biomaterials. Their biocompatibility and the ability to engineer the functionality have led to promising results in regenerative therapy. This review was intended to illuminate those who wish to envisage the niche translational research in regenerative therapy by summarizing the various explored types, chemistry, mechanisms, stimuli receptivity, and other advancements of supramolecular systems.

Development of tannin-bridged cerium oxide microcubes-chitosan cryogel as a multifunctional wound dressing

Efficient resolution of oxidative stress, inflammation, and bacterial infections is crucial for wound healing. To surmount these problems, tannic acid (TA)-bridged CeO₂ microcubes and chitosan (CS) (CS-TA@CeO₂) cryogel was fabricated through hydrogen bonding interactions as a multifunctional wound dressing. Successful introduction and uniform incorporation TA@CeO₂ microtubules enter the CS network. Thus-obtained CS-TA@CeO₂ cryogels displayed a suitable porous structure and swelling rate. Cryogels has excellent tissue adhesion, blood cell coagulation and hemostasis, anti-infection, and cell recruitment functions. In addition, the cryogel also showed good antibacterial activity against gram-positive bacteria and gram-negative bacteria. Based on the in vivo study of the multifunctional mixed cryogels, it promotes fibroblasts' adhesion and proliferation and significantly improves cell proliferation and tissue remodelling in wound beds. Furthermore, the chronic wound healing process in infected full-thickness skin defect models showed that cryogels significantly enhanced angiogenesis, collagen deposition and granulation tissue formation by providing a large amount of antioxidant activity. Therefore, this multifunctional mixed cryogels has potential clinical application value.

Bio-inspired hydrogels with fibrous structure: A review on design and biomedical applications

Numerous tissues in the human body have fibrous structures, including the extracellular matrix, muscles, and heart, which perform critical biological functions and have exceptional mechanical strength. Due to their high-water content, softness, biocompatibility and elastic nature, hydrogels resemble biological tissues. Traditional hydrogels, on the other hand, have weak mechanical properties and lack tissue-like fibrous structures, limiting their potential applications. Thus, bio-inspired hydrogels with fibrous architectures have piqued the curiosity of biomedical researchers. Here, we review fabrication strategies for fibrous hydrogels and their recent progress in the biomedical fields of wound dressings, drug delivery, tissue engineering scaffolds and bioadhesives. Challenges and future perspectives are also discussed.

A Review of Sustained Drug Release Studies from Nanofiber Hydrogels

Polymer nanofibers have exceptionally high surface area. This is advantageous compared to bulk polymeric structures, as nanofibrils increase the area over which materials can be transported into and out of a system, via diffusion and active transport. On the other hand, since hydrogels possess a degree of flexibility very similar to natural tissue, due to their significant water content, hydrogels made from natural or biodegradable macromolecular systems can even be injectable into the human body. Due to unique interactions with water, hydrogel transport properties can be easily modified and tailored. As a result, combining nanofibers with hydrogels would truly advance biomedical applications of hydrogels, particularly in the area of sustained drug delivery. In fact, certain nanofiber networks can be transformed into hydrogels directly without the need for a hydrogel enclosure. This review discusses recent advances in the fabrication and application of biomedical nanofiber hydrogels with a strong emphasis on drug release. Most of the drug release studies and recent advances have so far focused on self-gelling nanofiber systems made from peptides or other natural proteins loaded with cancer drugs. Secondly, polysaccharide nanofiber hydrogels are being investigated, and thirdly, electrospun biodegradable polymer networks embedded in polysaccharide-based hydrogels are becoming increasingly popular. This review shows that a major outcome from these works is that nanofiber hydrogels can maintain drug release rates exceeding a few days, even extending into months, which is an extremely difficult task to achieve without the nanofiber texture. This review also demonstrates that some publications still lack careful rheological studies on nanofiber hydrogels; however, rheological properties of hydrogels can influence cell function, mechano-transduction, and cellular interactions such as growth, migration, adhesion, proliferation, differentiation, and morphology. Nanofiber hydrogel rheology becomes even more critical for 3D or 4D printable systems that should maintain sustained drug delivery rates.

Repair of Peripheral Nerve Injury Using Hydrogels Based on Self-Assembled Peptides

Peripheral nerve injury often occurs in young adults and is characterized by complex regeneration mechanisms, poor prognosis, and slow recovery, which not only creates psychological obstacles for the patients but also causes a significant burden on society, making it a fundamental problem in clinical medicine. Various steps are needed to promote regeneration of the peripheral nerve. As a bioremediation material, self-assembled peptide (SAP) hydrogels have attracted international attention. They can not only be designed with different characteristics but also be applied in the repair of peripheral nerve injury by promoting cell proliferation or drug-loaded sustained release. SAP hydrogels are widely used in tissue engineering and have become the focus of research. They have extensive application prospects and are of great potential biological value. In this paper, the application of SAP hydrogel in peripheral nerve injury repair is reviewed, and the latest progress in peptide composites and fabrication techniques are discussed.