Polypeptide-based self-healing hydrogels: Design and biomedical applications

Highly stretchable, self-healing, antibacterial, conductive, and amylopectin-enhanced hydrogels with gallium droplets loading as strain sensors

In this study, we address the challenge of developing highly conductive hydrogels with enhanced stretchability for use in wearable sensors, which are critical for the precise detection of human motion and subtle physiological strains. Our novel approach utilizes amylopectin, a biopolymer, for the uniform integration of liquid metal gallium into the hydrogel matrix. This integration results in a conductive hydrogel characterized by remarkable elasticity (up to 7100 % extensibility) and superior electrical conductance (Gauge Factor = 31.4), coupled with a minimal detection limit of less than 0.1 % and exceptional durability over 5000 cycles. The hydrogel demonstrates significant antibacterial activity, inhibiting microbial growth in moist environments, thus enhancing its applicability in medical settings. Employing a synthesis process that involves ambient condition polymerization of acrylic acid, facilitated by a hydrophobic associative framework, this hydrogel stands out for its rapid gelation and robust mechanical properties. The potential applications of this hydrogel extend beyond wearable sensors, promising advancements in human-computer interaction through technologies like wireless actuation of robotic systems. This study not only introduces a viable material for current wearable technologies but also sets a foundation for future innovations in bio-compatible sensors and interactive devices.

Hydrogels: a promising therapeutic platform for inflammatory skin diseases treatment

Inflammatory skin diseases, such as psoriasis and atopic dermatitis, pose significant health challenges due to their long-lasting nature, potential for serious complications, and significant health risks, which requires treatments that are both effective and exhibit minimal side effects. Hydrogels offer an innovative solution due to their biocompatibility, tunability, controlled drug delivery capabilities, enhanced treatment adherence and minimized side effects risk. This review explores the mechanisms that guide the design of hydrogel therapeutic platforms from multiple perspectives, focusing on the components of hydrogels, their adjustable physical and chemical properties, and their interactions with cells and drugs to underscore their clinical potential. We also examine various therapeutic agents for psoriasis and atopic dermatitis that can be integrated into hydrogels, including traditional drugs, novel compounds targeting oxidative stress, small molecule drugs, biologics, and emerging therapies, offering insights into their mechanisms and advantages. Additionally, we review clinical trial data to evaluate the effectiveness and safety of hydrogel-based treatments in managing psoriasis and atopic dermatitis under complex disease conditions. Lastly, we discuss the current challenges and future opportunities for hydrogel therapeutics in treating psoriasis and atopic dermatitis, such as improving skin barrier penetration and developing multifunctional hydrogels, and highlight emerging opportunities to enhance long-term safety and stability.

Compact Polyelectrolyte Complexes of Poly(l-Lysine) and Anionic Polysaccharides

Compact polyelectrolyte complexes (CoPECs) can exhibit mechanical properties similar to those of biological tissues and other interesting properties, such as self-healing. To date, a variety of CoPECs prepared from synthetic polyelectrolytes have been investigated, but there are very few examples based entirely on biopolymers. We describe here an investigation of CoPECs based on poly(l-lysine) (PLL) with sodium hyaluronate (HA) and alginate (Alg). A 2:1 ratio of cation:anion and 0.25 M NaBr was beneficial for the formation of viscoelastic PLL-HA CoPECs, with the favorable ratio attributed to the spacing of carboxylates on HA being one every two saccharide units. In contrast, 1.0 M NaBr and a 1:1 ratio were better for PLL-Alg CoPECs. Both CoPECs swelled or retained a constant volume when immersed in hypertonic media, but contracted in hypotonic media. The loading of molecules into the PLL-HA (2:1) CoPECs was investigated. Higher loadings were achieved for anionic molecules compared to cations, presumably due to the excess cationic binding sites on the networks. The times required for full release of the molecules ranged from less than 2 h for neutral paracetamol to about 48 h for crystal violet and diclofenac.

The application of hydrogels for enamel remineralization

Enamel is composed of numerous uniformly wide, well-oriented hydroxyapatite crystals. It possesses an acellular structure that cannot be repaired after undergoing damage. Therefore, remineralization after enamel defects has become a focal point of research. Hydrogels, which are materials with three-dimensional structures derived from cross-linking polymers, have garnered significant attention in recent studies. Their exceptional properties make them valuable in the application of enamel remineralization. In this review, we summarize the structure and formation of enamel, present the design considerations of hydrogels for enamel remineralization, explore diverse hydrogels types in this context, and finally, shed light on the potential future applications in this field.

Towards food-derived self-assembling peptide-based hydrogels: Insights into preparation, characterization and mechanism

Food proteins represent a vital source of self-assembling peptides, with hydrogels constructed through peptide self-assembly exhibiting widespread utility in the food sector. This review aims to provide a recent research progress in preparation and characterization of hydrogels from food-derived peptides. Also, the self-assembly mechanisms and the impact of factors are discussed. Presently, food-derived self-assembling peptide-based hydrogels can be synthesized using either physical or chemical methodologies and evaluated through methodologies such as microscopic, spectroscopic, and rheological assessment. The self-assembly of food-derived peptides is hierarchically formed by non-covalent interactions, including hydrogen bond and hydrophobic interactions, where variables such as temperature and pH intricately modulate the assembly mechanism. The association between peptide sequence and hydrogel structure in the self-assembly mechanism is also discussed, which remains to be further explored. The present review contributes to application of food-derived peptide-based hydrogels in the fields of food, nutrition and material sciences.

Fabrication of a self-healing hydrogel with antibacterial activity using host-guest interactions between dopamine-modified alginate and β-cyclodextrin dimer

Self-healing hydrogels possess an ability to recover their functionality after experiencing damage by regenerating cross-links. The main challenge in making self-healing hydrogels based on host-guest (HG) interactions is their limited mechanical strength, which can be solved using beta-cyclodextrin dimers (β-CDsD). Here, β-CDsD as a host cross-linker was used to increase the mechanical property of the HG interactions. Alginate with acceptable biocompatibility was modified by dopamine (ALG-DOP) and employed as a guest polymer. Self-healing hydrogel was developed between them, and Ag nanoparticles were added to create an antibacterial activity. Dopamine with appropriate size and suitable adhesiveness established HG interactions with β-CDsD, and cells were able to grow well on hydrogel. This hydrogel showed an impressive self-healing capability <5 min. These hydrogels revealed a respectable porosity from 15 to 55 μm essential for exchanging the substances required for cell growth and cell waste elimination. Biocompatibility was investigated against NIH 3 T3 fibroblasts cells, and the results showed that the cells grew well. The in vitro release of curcumin from the hydrogel was examined in PBS at pH of 7.4. The hydrogel can be a perfect candidate for controlled drug release, and wound-dressing due to self-healing property, antibacterial activity, adhesion, and biocompatibility.

Logic-Based Strategy for Spatiotemporal Release of Dual Extracellular Vesicles in Osteoarthritis Treatment

To effectively treat osteoarthritis (OA), the existing inflammation must be reduced before the cartilage damage can be repaired; this cannot be achieved with a single type of extracellular vesicles (EVs). Here, a hydrogel complex with logic-gates function is proposed that can spatiotemporally controlled release two types of EVs: interleukin 10 (IL-10)+ EVs to promote M2 polarization of macrophage, and SRY-box transcription factor 9 (SOX9)+ EVs to increase cartilage matrix synthesis. Following dose-of-action screening, the dual EVs are loaded into a matrix metalloporoteinase 13 (MMP13)-sensitive self-assembled peptide hydrogel (KM13E) and polyethylene glycol diacrylate/gelatin methacryloyl-hydrogel microspheres (PGE), respectively. These materials are mixed to form a "microspheres-in-gel" KM13E@PGE system. In vitro, KM13E@PGE abruptly released IL-10+ EVs after 3 days and slowly released SOX9+ EVs for more than 30 days. In vivo, KM13E@PGE increased the CD206+ M2 macrophage proportion in the synovial tissue and decreased the tumor necrosis factor-α and IL-1β levels. The aggrecan and SOX9 expressions in the cartilage tissues are significantly elevated following inflammation subsidence. This performance is not achieved using anti-inflammatory or cartilage repair therapy alone. The present study provides an injectable, integrated delivery system with spatiotemporal control release of dual EVs, and may inspire logic-gates strategies for OA treatment.

Antibacterial polylysine-containing hydrogels for hemostatic and wound healing applications: preparation methods, current advances and future perspectives

The treatment of various types of wounds such as dermal wounds, multidrug resistant bacteria-infected wounds, and chronic diabetic wounds is one of the critical challenges facing healthcare systems. Delayed wound healing can impose a remarkable burden on patients and health care professionals. In this case, given their unique three-dimensional porous structure, biocompatibility, high hydrophilicity, capability to provide a moist environment while absorbing wound exudate, permeability to both gas and oxygen, and tunable mechanical properties, hydrogels with antibacterial function are one of the most promising candidates for wound healing applications. Polylysine is a cationic polymer with the advantages of inherent antibacterial properties, biodegradability, and biocompatibility. Therefore, its utilization to engineer antibacterial hydrogels for accelerating wound healing is of great interest. In this review, we initially discuss polylysine properties, and then focus on the most recent advances in polylysine-containing hydrogels (since 2016) prepared using various chemical and physical crosslinking methods for hemostasis and wound healing applications. Finally, the challenges and future directions in the engineering of these antibacterial hydrogels for wound healing are discussed.

Genetically Fusing Order-Promoting and Thermoresponsive Building Blocks to Design Hybrid Biomaterials

The unique biophysical and biochemical properties of intrinsically disordered proteins (IDPs) and their recombinant derivatives, intrinsically disordered protein polymers (IDPPs) offer opportunities for producing multistimuli-responsive materials; their sequence-encoded disorder and tendency for phase separation facilitate the development of multifunctional materials. This review highlights the strategies for enhancing the structural diversity of elastin-like polypeptides (ELPs) and resilin-like polypeptides (RLPs), and their self-assembled structures via genetic fusion to ordered motifs such as helical or beta sheet domains. In particular, this review describes approaches that harness the synergistic interplay between order-promoting and thermoresponsive building blocks to design hybrid biomaterials, resulting in well-structured, stimuli-responsive supramolecular materials ordered on the nanoscale.

Fluoride-Ion-Responsive Sol-Gel Transition in an L-Cysteine/AgNO3 System: Self-Assembly Peculiarities and Anticancer Activity

Supramolecular hydrogels based on low-molecular-weight compounds are a unique class of so-called "soft" materials, formed by weak non-covalent interactions between precursors at their millimolar concentrations. Due to the variety of structures that can be formed using different low-molecular-weight gelators, they are widely used in various fields of technology and medicine. In this study, we report for the first time an unusual self-assembly process of mixing a hydrosol obtained from L-cysteine and silver nitrate (cysteine-silver sol-CSS) with sodium halides. Modern instrumental techniques such as viscosimetry, UV spectroscopy, dynamic light scattering, zeta potential measurements, SEM and EDS identified that adding fluoride anions to CSS is able to form stable hydrogels of a thixotropic nature, while Cl-, Br- and I- lead to precipitation. The self-assembly process proceeds using a narrow concentration range of F-. An increase in the fluoride anion content in the system leads to a change in the gel network morphology from elongated structures to spherical ones. This fact is reflected in a decrease in the gel viscosity and a number of gel-sol-gel transition cycles. The mechanism of F-'s interaction with hydrosol includes the condensation of anions on the positive surface of the CSS nanoparticles, their binding via electrostatic forces and the formation of a resulting gel carcass. In vitro analysis showed that the hydrogels suppressed human squamous carcinoma cells at a micromolar sample concentration. The obtained soft gels could have potential applications against cutaneous malignancy and as carriers for fluoride anion and other bioactive substance delivery.

Self-healing hydrogels for enhancing chemotherapy drug efficacy: Advancements in anti-sarcoma and carcinoma therapies and clinical trial feasibility

•Site-specific administration is key for optimizing anticancer drug administration; self-healing hydrogels may allow this at reasonable costs and reproducibility.•Self-healing hydrogels have several real-world therapeutic applications, including drug administration.•Self-healing hydrogels are yet to be utilized for chemotherapy drug administration in clinical trials.•Clinical research on using self-healing hydrogels in anticancer therapeutics is feasible and valid compared to other advances in anticancer drug administration.

Practical Applications of Self-Healing Polymers Beyond Mechanical and Electrical Recovery

Self-healing polymeric materials, which can repair physical damage, offer promising prospects for protective applications across various industries. Although prolonged durability and resource conservation are key advantages, focusing solely on mechanical recovery may limit the market potential of these materials. The unique physical properties of self-healing polymers, such as interfacial reduction, seamless connection lines, temperature/pressure responses, and phase transitions, enable a multitude of innovative applications. In this perspective, the diverse applications of self-healing polymers beyond their traditional mechanical strength are emphasized and their potential in various sectors such as food packaging, damage-reporting, radiation shielding, acoustic conservation, biomedical monitoring, and tissue regeneration is explored. With regards to the commercialization challenges, including scalability, robustness, and performance degradation under extreme conditions, strategies to overcome these limitations and promote successful industrialization are discussed. Furthermore, the potential impacts of self-healing materials on future research directions, encompassing environmental sustainability, advanced computational techniques, integration with emerging technologies, and tailoring materials for specific applications are examined. This perspective aims to inspire interdisciplinary approaches and foster the adoption of self-healing materials in various real-life settings, ultimately contributing to the development of next-generation materials.

Advancements in Regenerative Hydrogels in Skin Wound Treatment: A Comprehensive Review

This state-of-the-art review explores the emerging field of regenerative hydrogels and their profound impact on the treatment of skin wounds. Regenerative hydrogels, composed mainly of water-absorbing polymers, have garnered attention in wound healing, particularly for skin wounds. Their unique properties make them well suited for tissue regeneration. Notable benefits include excellent water retention, creating a crucially moist wound environment for optimal healing, and facilitating cell migration, and proliferation. Biocompatibility is a key feature, minimizing adverse reactions and promoting the natural healing process. Acting as a supportive scaffold for cell growth, hydrogels mimic the extracellular matrix, aiding the attachment and proliferation of cells like fibroblasts and keratinocytes. Engineered for controlled drug release, hydrogels enhance wound healing by promoting angiogenesis, reducing inflammation, and preventing infection. The demonstrated acceleration of the wound healing process, particularly beneficial for chronic or impaired healing wounds, adds to their appeal. Easy application and conformity to various wound shapes make hydrogels practical, including in irregular or challenging areas. Scar minimization through tissue regeneration is crucial, especially in cosmetic and functional regions. Hydrogels contribute to pain management by creating a protective barrier, reducing friction, and fostering a soothing environment. Some hydrogels, with inherent antimicrobial properties, aid in infection prevention, which is a crucial aspect of successful wound healing. Their flexibility and ability to conform to wound contours ensure optimal tissue contact, enhancing overall treatment effectiveness. In summary, regenerative hydrogels present a promising approach for improving skin wound healing outcomes across diverse clinical scenarios. This review provides a comprehensive analysis of the benefits, mechanisms, and challenges associated with the use of regenerative hydrogels in the treatment of skin wounds. In this review, the authors likely delve into the application of rational design principles to enhance the efficacy and performance of hydrogels in promoting wound healing. Through an exploration of various methodologies and approaches, this paper is poised to highlight how these principles have been instrumental in refining the design of hydrogels, potentially revolutionizing their therapeutic potential in addressing skin wounds. By synthesizing current knowledge and highlighting potential avenues for future research, this review aims to contribute to the advancement of regenerative medicine and ultimately improve clinical outcomes for patients with skin wounds.

Engineering Self-Assembling Peptide Hydrogel to Enhance the Capacity of Dendritic Cells to Activate In Vivo T-Cell Immunity

The efficacy of the dendritic cell (DC) has failed to meet expectations thus far, and crucial problems such as the immature state of DCs, low targeting efficiency, insufficient number of dendritic cells, and microenvironment are still the current focus. To address these problems, we developed two self-assembling peptides, RLDI and RQDT, that mimic extracellular matrix (ECM). These peptides can be self-assembled into highly ordered three-dimensional nanofiber scaffold structures, where RLDI can form gelation immediately. In addition, we found that RLDI and RQDT enhance the biological function of DCs, including releasing antigens sustainably, adhering to DCs, promoting the maturation of DCs, and increasing the ability of DC antigen presentation. Moreover, peptide hydrogel-based DC treatment significantly achieved prophylactic and treatment effects on colon cancer. These results have certain implications for the design of new broad-spectrum vaccines in the future.

3D Printing of Self-Healing Materials

This review article presents a comprehensive overview of the latest advances in the field of 3D printable structures with self-healing properties. Three-dimensional printing (3DP) is a versatile technology that enables the rapid manufacturing of complex geometric structures with precision and functionality not previously attainable. However, the application of 3DP technology is still limited by the availability of materials with customizable properties specifically designed for additive manufacturing. The addition of self-healing properties within 3D printed objects is of high interest as it can improve the performance and lifespan of structural components, and even enable the mimicking of living tissues for biomedical applications, such as organs printing. The review will discuss and analyze the most relevant results reported in recent years in the development of self-healing polymeric materials that can be processed via 3D printing. After introducing the chemical and physical self-healing mechanism that can be exploited, the literature review here reported will focus in particular on printability and repairing performances. At last, actual perspective and possible development field will be critically discussed.

Self-healing amino acid-bearing acrylamides/n-butyl acrylate copolymers via multiple noncovalent bonds

Four amino acid-bearing acrylamides, N-acryloyl-l-threonine (AThrOH), N-acryloyl-l-glutamic acid (AGluOH), N-acryloyl-l-phenylalanine (APheOH), and N-acryloyl-l, l-diphenylalanine (APhePheOH), were selected for copolymerization with n-butyl acrylate (nBA) to develop amino acid-based self-healable copolymers. A series of copolymers comprising amino acid-bearing acrylamides and nBA with tunable comonomer compositions and molecular weights were synthesized by free radical and reversible addition-fragmentation chain-transfer copolymerization. Self-healing and mechanical properties originated from the noncovalent bonds between the carboxyl, hydroxyl, and amide groups, and π-π stacking interactions among the amino acid residues in the side chains were evaluated. Among these copolymers, P(nBA-co-AGluOH) with suitable comonomer compositions and molecular weights (nBA : AGluOH = 82 : 18, Mn = 18 300, Mw/Mn = 2.58) exhibited good mechanical properties (modulus of toughness = 17.3 MJ m-3) and self-healing under ambient conditions. The multiple noncovalent bonds of P(nBA-co-AGluOH)s were also efficient in improving the optical properties with an enhanced refractive index and good transparency.

Research progress on hydrogel-based drug therapy in melanoma immunotherapy

Melanoma is one of the most aggressive skin tumors, and conventional treatment modalities are not effective in treating advanced melanoma. Although immunotherapy is an effective treatment for melanoma, it has disadvantages, such as a poor response rate and serious systemic immune-related toxic side effects. The main solution to this problem is the use of biological materials such as hydrogels to reduce these side effects and amplify the immune killing effect against tumor cells. Hydrogels have great advantages as local slow-release drug carriers, including the ability to deliver antitumor drugs directly to the tumor site, enhance the local drug concentration in tumor tissue, reduce systemic drug distribution and exhibit good degradability. Despite these advantages, there has been limited research on the application of hydrogels in melanoma treatment. Therefore, this article provides a comprehensive review of the potential application of hydrogels in melanoma immunotherapy. Hydrogels can serve as carriers for sustained drug delivery, enabling the targeted and localized delivery of drugs with minimal systemic side effects. This approach has the potential to improve the efficacy of immunotherapy for melanoma. Thus, the use of hydrogels as drug delivery vehicles for melanoma immunotherapy has great potential and warrants further exploration. [BMB Reports 2024; 57(2): 71-78].

Development of alginate macroporous hydrogels using sacrificial CaCO3 particles for enhanced hemostasis

Polymeric hydrogels have increasingly garnered attention in the field of hemostasis. However, there remains a lack of targeted development and evaluation of non-dense polymeric hydrogels with physically incorporated pores to enhance hemostasis. Here, we present a facile route to macroporous alginate hydrogels using acid-induced CaCO3 dissolution to provide Ca2+ for alginate gelation and CO2 bubbles for subsequent macropore formation. The as-prepared pore structure in the hydrogels and its formation mechanisms were characterized through microscopic imaging and nitrogen adsorption/desorption tests. Functional analyses revealed that the macroporous hydrogels exhibited improved rheology, blood absorption, coagulation factor delivery, and platelet aggregation. Ultimately, the introduction of pores significantly enhanced the hemostatic effectiveness of alginate hydrogels in vivo, as demonstrated in rat tail amputation and liver injury models, leading to a reduction in blood loss of up to 77 % or a decrease in bleeding time of up to 88 %. Notably, hydrogels with higher porosity achieved with a CaCO3 to alginate ratio of 40 % outperformed those with lower porosity in the aforementioned properties. Furthermore, these improvements were found to be biocompatible and elicited minimal inflammation. Our findings underscore the potential of a simple porous hydrogel design to enhance hemostasis efficacy by physically incorporating macropores.

Wound microenvironment-responsive dually cross-linked nanofibrillar peptide hydrogels for efficient hemostatic control and multi-faceted wound management

The wound microenvironment-responsive hydrogel, featuring a dually cross-linked architecture, offers distinct advantages in the realm of drug delivery due to its exceptional mechanical properties and responsiveness to stimuli. In this investigation, a versatile dually cross-linked hydrogel was synthesized. The initial framework was established through non-covalent interactions employing a self-assembling peptide indomethacin-Gly-Phe-Phe-Tyr-Gly-Arg-Gly-Asp (abbreviated as IDM-1), while the second framework underwent chemical cross-linking of chitosan (CS) mediated by genipin. This dually-network arrangement significantly bolstered the structure, proving effective for hemostatic control. In addition, hydrogels can be triggered for degradation by proteases highly expressed in the wound microenvironment, releasing drugs like indomethacin (IDM) and CS. This characteristic introduced efficient multi-faceted wound management in vitro and in vivo, such as anti-inflammatory and antibacterial activities, ultimately augmenting the wound healing process. Thus, the development of a dually cross-linked hydrogel that enables smart drug release triggered by specific wound microenvironment presents considerable potential within the realm of wound management.

Supramolecular hydrogels for wound repair and hemostasis

The unique network characteristics and stimuli responsiveness of supramolecular hydrogels have rendered them highly advantageous in the field of wound dressings, showcasing unprecedented potential. However, there are few reports on a comprehensive review of supramolecular hydrogel dressings for wound repair and hemostasis. This review first introduces the major cross-linking methods for supramolecular hydrogels, which includes hydrogen bonding, electrostatic interactions, hydrophobic interactions, host-guest interactions, metal ligand coordination and some other interactions. Then, we review the advanced materials reported in recent years and then summarize the basic principles of each cross-linking method. Next, we classify the network structures of supramolecular hydrogels before outlining their forming process and propose their potential future directions. Furthermore, we also discuss the raw materials, structural design principles, and material characteristics used to achieve the advanced functions of supramolecular hydrogels, such as antibacterial function, tissue adhesion, substance delivery, anti-inflammatory and antioxidant functions, cell behavior regulation, angiogenesis promotion, hemostasis and other innovative functions in recent years. Finally, the existing problems as well as future development directions of the cross-linking strategy, network design, and functions in wound repair and hemostasis of supramolecular hydrogels are discussed. This review is proposed to stimulate further exploration of supramolecular hydrogels on wound repair and hemostasis by researchers in the future.

Recent advances in anti-inflammatory active components and action mechanisms of natural medicines

Inflammation is a series of reactions caused by the body's resistance to external biological stimuli. Inflammation affects the occurrence and development of many diseases. Anti-inflammatory drugs have been used widely to treat inflammatory diseases, but long-term use can cause toxic side-effects and affect human functions. As immunomodulators with long-term conditioning effects and no drug residues, natural products are being investigated increasingly for the treatment of inflammatory diseases. In this review, we focus on the inflammatory process and cellular mechanisms in the development of diseases such as inflammatory bowel disease, atherosclerosis, and coronavirus disease-2019. Also, we focus on three signaling pathways (Nuclear factor-kappa B, p38 mitogen-activated protein kinase, Janus kinase/signal transducer and activator of transcription-3) to explain the anti-inflammatory effect of natural products. In addition, we also classified common natural products based on secondary metabolites and explained the association between current bidirectional prediction progress of natural product targets and inflammatory diseases.

Polypeptide-Based Systems: From Synthesis to Application in Drug Delivery

Synthetic polypeptides are biocompatible and biodegradable macromolecules whose composition and architecture can vary over a wide range. Their unique ability to form secondary structures, as well as different pathways of modification and biofunctionalization due to the diversity of amino acids, provide variation in the physicochemical and biological properties of polypeptide-containing materials. In this review article, we summarize the advances in the synthesis of polypeptides and their copolymers and the application of these systems for drug delivery in the form of (nano)particles or hydrogels. The issues, such as the diversity of polypeptide-containing (nano)particle types, the methods for their preparation and drug loading, as well as the influence of physicochemical characteristics on stability, degradability, cellular uptake, cytotoxicity, hemolysis, and immunogenicity of polypeptide-containing nanoparticles and their drug formulations, are comprehensively discussed. Finally, recent advances in the development of certain drug nanoformulations for peptides, proteins, gene delivery, cancer therapy, and antimicrobial and anti-inflammatory systems are summarized.

An antibacterial and healing-promoting collagen fibril constructed by the simultaneous strategy of fibril reconstitution and ε-polylysine anchoring for infected wound repair

The development of antibacterial dressings has attracted much attention to address the disordered wound healing caused by bacterial infection. Constructing dressings that have desirable antibacterial activity and could promote wound healing is important for infected wound repair. Inspired by the role of the key regulator collagen fibrils with D-periodic functional domains in the physiological wound healing process, we developed an antibacterial and wound healing-promoting collagen fibril with a structure highly similar to natural collagen in ECM and inherent antibacterial activity by the simultaneous strategy of fibril reconstitution and the antibacterial agent ε-polylysine (ε-PL) anchoring. Accompanied by the fibrillogenesis of collagen molecules, the anchorage of ε-PL into collagen fibrils was actualized through the formation of the covalent bond catalyzed by transglutaminase (TGase) between ε-PL and collagen. The collagen fibril possessed natural D-periodicity and achieved 20% ε-PL graft yield by co-assembling collagen/ε-PL mediated by 25 U g-1 TGase, which showed a satisfactory proliferation of L929 fibroblasts and sustained inhibition rates above 90% against E. coli and S. aureus. The rat S. aureus-infected dermal wound model further demonstrated that the reconstituted antibacterial collagen fibril visibly promoted re-epithelialization, new collagen deposition, and angiogenesis by down-regulating the inflammatory-relative gene IL-6 and up-regulating the relative activity factor expression of CD31, achieving accelerated infected wound healing with 61.89% ± 3.96% wound closure on postoperative day 7 and full closure on day 14.

Current Advances in Stimuli-Responsive Hydrogels as Smart Drug Delivery Carriers

In recent years, significant advancements in the field of advanced materials and hydrogel engineering have enabled the design and fabrication of smart hydrogels and nanogels that exhibit sensitivity to specific signals or pathological conditions, leading to a wide range of applications in drug delivery and disease treatment. This comprehensive review aims to provide an in-depth analysis of the stimuli-responsive principles exhibited by smart hydrogels in response to various triggers, such as pH levels, temperature fluctuations, light exposure, redox conditions, or the presence of specific biomolecules. The functionality and performance characteristics of these hydrogels are highly influenced by both their constituent components and fabrication processes. Key design principles, their applications in disease treatments, challenges, and future prospects were also discussed. Overall, this review aims to contribute to the current understanding of gel-based drug delivery systems and stimulate further research in this rapidly evolving field.

Hydrogel-based treatments for spinal cord injuries

Spinal cord injury (SCI) is characterized by damage resulting in dysfunction of the spinal cord. Hydrogels are common biomaterials that play an important role in the treatment of SCI. Hydrogels are biocompatible, and some have electrical conductivity that are compatible with spinal cord tissues. Hydrogels have a high drug-carrying capacity, allowing them to be used for SCI treatment through the loading of various types of active substances, drugs, or cells. We first discuss the basic anatomy and physiology of the human spinal cord and briefly discuss SCI and its treatment. Then, we describe different treatment strategies for SCI. We further discuss the crosslinking methods and classification of hydrogels and detail hydrogel biomaterials prepared using different processing methods for the treatment of SCI. Finally, we analyze the future applications and limitations of hydrogels for SCI. The development of biomaterials opens up new possibilities and options for the treatment of SCI. Thus, our findings will inspire scholars in related fields and promote the development of hydrogel therapy for SCI.

Advances in preparation and application of antibacterial hydrogels

Bacterial infections, especially those caused by drug-resistant bacteria, have seriously threatened human life and health. There is urgent to develop new antibacterial agents to reduce the problem of antibiotics. Biomedical materials with good antimicrobial properties have been widely used in antibacterial applications. Among them, hydrogels have become the focus of research in the field of biomedical materials due to their unique three-dimensional network structure, high hydrophilicity, and good biocompatibility. In this review, the latest research progresses about hydrogels in recent years were summarized, mainly including the preparation methods of hydrogels and their antibacterial applications. According to their different antibacterial mechanisms, several representative antibacterial hydrogels were introduced, such as antibiotics loaded hydrogels, antibiotic-free hydrogels including metal-based hydrogels, antibacterial peptide and antibacterial polymers, stimuli-responsive smart hydrogels, and light-mediated hydrogels. In addition, we also discussed the applications and challenges of antibacterial hydrogels in biomedicine, which are expected to provide new directions and ideas for the application of hydrogels in clinical antibacterial therapy.

An injectable supramolecular hydrogel as a self-drug-delivery system for local chemoimmunotherapy against melanoma

Skin-cancer melanoma caused 57k death in 2020. Some of the available therapies are: topical application of a gel loaded with an anti-skin cancer drug and intravenous injection of immune cytokines; however, both the approaches have drawbacks such as inefficient internalization of the drug in cancer cells and a short half-life with severe side effects, respectively. Interestingly, we observed for the first time that a subcutaneously implanted hydrogel designed and synthesized by coordinating NSAIDs and 5-AP with Zn(II) can effectively combat melanoma cell (B16-F10)-induced tumors in C57BL/6 mice. Both in vitro and in vivo results show that it can effectively reduce PGE2 expression, consequently upregulating IFN-γ and IL-12 that eventually engage M1-macrophages for activating T cells (CD8+), triggering apoptosis. This unique all-in-one self-drug-delivery approach, wherein the hydrogel implant is made from the drug molecules itself providing both chemotherapy and immunotherapy in combating deadly melanoma, highlights the supramolecular chemistry-based bottom-up approach in cancer therapy.

Highly stretchable, fast self-healing nanocellulose hydrogel combining borate ester bonds and acylhydrazone bonds

Self-healing hydrogels have received considerable attention as a promising material for flexible electronic devices given their mechanical durability and structurally tunable properties. In this study, a highly stretchable self-healing hydrogel with dual cross-linking network was developed via borate ester bonds generated by polyvinyl alcohol and borax, and acylhydrazone bonds formed by aldehyde nanocellulose with adipic acid dihydrazide-modified alginate. Compared with the single network hydrogel composed of polyvinyl alcohol and borax, the introduction of dynamic acylhydrazone bonds greatly increases the flexibility of the hydrogel. The elongation rate increased from 480 % to approximately 1440 %, and the self-healing efficiency increased from 84.6 % to 92.7 % after healing for 60 min at ambient temperature without any stimulus. Moreover, the longer the self-healing time, the more evident the self-healing effect of the acylhydrazone bonds. In addition, electrical measurements confirmed a wide working strain range (ca.1000 %), durability, and reliability. Once assembled as a strain sensor, the hydrogel is able to monitor both large and subtle human motions. Besides, this hydrogel exhibited desirable biocompatibility, as demonstrated by in vitro cytotoxicity towards NIH 3T3 cells. These integrated properties make this nanocomposite hydrogel a promising candidate for future applications as green, flexible, and smart sensors.

Nanoparticle delivery of TFOs is a novel targeted therapy for HER2 amplified breast cancer

PURPOSE

The human EGFR2 (HER2) signaling pathway is one of the most actively studied targets in cancer transformation research. Ttriplex-forming oligonucleotides (TFOs) activate DNA damage and induce apoptosis. We aim to encapsulate TFO-HER2 with nano-particle ZW-128 to suppress breast cell growth in vitro and in vivo.

EXPERIMENTAL DESIGN

We designed a set of TFO fragments targeting HER2 and verified their effectiveness. We encapsulated TFO-HER2 in ZW-128 to form nano-drug TFO@ZW-128. Cell counting kit 8, flow cytometry, and western blotting were used to evaluate the effect of TFO@ZW-128 on cell proliferation and the expressions of related proteins. The ant-itumor effect of TFO@ZW-128 was evaluated in vivo using nude mice breast cancer model.

RESULTS

TFO@ZW-128 had efficient cellular uptake in amplified HER2 breast cancer cells. TFO@ZW-128 showed an 80-fold increase in TFO utilization compared with TFO-HER2 in the nude mouse breast cancer model. Meanwhile, TFO@ZW-128 dramatically inhibited the growth of HER2-overexpressing tumors compared with TFO-HER2 (P < 0.05). Furthermore, TFO@ZW-128-induced cell apoptosis was in a p53-independent manner.

CONCLUSIONS

In this study, we designed nano-drug TFO@ZW-128, which has proven effective and non-toxic in targeted therapy for ectopic HER2-expressing tumors.

Peptide hydrogels: Synthesis, properties, and applications in food science

Due to the unique and excellent biological, physical, and chemical properties of peptide hydrogels, their application in the biomedical field is extremely wide. The applications of peptide hydrogels are closely related to their unique responsiveness and excellent properties. However, its defects in mechanical properties, stability, and toxicity limit its application in the food field. In this review, we focus on the fabrication methods of peptide hydrogels through the physical, chemical, and biological stimulations. In addition, the functional design of peptide hydrogels by the incorporation with materials is discussed. Meanwhile, the excellent properties of peptide hydrogels such as the stimulus responsiveness, biocompatibility, antimicrobial properties, rheology, and stability are reviewed. Finally, the application of peptide hydrogel in the food field is summarized and prospected.

Self-healing hydrogels for bone defect repair

Severe bone defects can be caused by various factors, such as tumor resection, severe trauma, and infection. However, bone regeneration capacity is limited up to a critical-size defect, and further intervention is required. Currently, the most common clinical method to repair bone defects is bone grafting, where autografts are the "gold standard." However, the disadvantages of autografts, including inflammation, secondary trauma and chronic disease, limit their application. Bone tissue engineering (BTE) is an attractive strategy for repairing bone defects and has been widely researched. In particular, hydrogels with a three-dimensional network can be used as scaffolds for BTE owing to their hydrophilicity, biocompatibility, and large porosity. Self-healing hydrogels respond rapidly, autonomously, and repeatedly to induced damage and can maintain their original properties (i.e., mechanical properties, fluidity, and biocompatibility) following self-healing. This review focuses on self-healing hydrogels and their applications in bone defect repair. Moreover, we discussed the recent progress in this research field. Despite the significant existing research achievements, there are still challenges that need to be addressed to promote clinical research of self-healing hydrogels in bone defect repair and increase the market penetration.

One-Step Construction of Tryptophan-Derived Small Molecule Hydrogels for Antibacterial Materials

Amino acid-based hydrogels have received widespread attention because of their wide range of sources, biodegradability, and biocompatibility. Despite considerable progress, the development of such hydrogels has been limited by critical problems such as bacterial infection and complex preparation. Herein, by using the non-toxic gluconolactone (GDL) to adjust the pH of the solution to induce the rapid self-assembly of N-[(benzyloxy)carbonyl]-L-tryptophan (ZW) to form a three-dimensional (3D) gel network, we developed a stable and effective self-assembled small-molecule hydrogel. Characterization assays and molecular dynamics studies indicate that π-π stacking and hydrogen bonding are the main drivers of self-assembly between ZW molecules. In vitro experiments further confirmed this material's sustained release properties, low cytotoxicity, and excellent antibacterial activity, particularly against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. This study provides a different and innovative perspective for the further development of antibacterial materials based on amino acid derivatives.

Carbon Dot-Based Hydrogels: Preparations, Properties, and Applications

Hydrogels have extremely high moisture content, which makes it very soft and excellently biocompatible. They have become an important soft material and have a wide range of applications in various fields such as biomedicine, bionic smart material, and electrochemistry. Carbon dot (CD)-based hydrogels are based on carbon dots (CDs) and auxiliary substances, forming a gel material with comprehensive properties of individual components. CDs embedding in hydrogels could not only solve their aggregation-caused quenching (ACQ) effect, but also manipulate the properties of hydrogels and even bring some novel properties, achieving a win-win situation. In this review, the preparation methods, formation mechanism, and properties of CD-based hydrogels, and their applications in biomedicine, sensing, adsorption, energy storage, and catalysis -are summarized. Finally, a brief discussion on future research directions of CD-based hydrogels will be given.

Human urine-derived stem cell exosomes delivered via injectable GelMA templated hydrogel accelerate bone regeneration

The key to critical bone regeneration in tissue engineering relies on an ideal bio-scaffold coated with a controlled release of growth factors. Gelatin methacrylate (GelMA) and Hyaluronic acid methacrylate (HAMA) have been a novel topic of interest in bone regeneration while introducing appropriate nano-hydroxyapatite (nHAP) to improve its mechanical properties. And the exosomes derived from human urine-derived stem cells (human ^USCEXOs) have also been reported to promote osteogenesis in tissue engineering. The present study aimed to design a new GelMA-HAMA/nHAP composite hydrogel as a drug delivery system. The ^USCEXOs were encapsulated and slow-released in the hydrogel for better osteogenesis. The characterization of the GelMA-based hydrogel showed excellent controlled release performance and appropriate mechanical properties. The in vitro studies showed that the ^USCEXOs/GelMA-HAMA/nHAP composite hydrogel could promote the osteogenesis of bone marrow mesenchymal stem cells (BMSCs) and the angiogenesis of endothelial progenitor cells (EPCs), respectively. Meanwhile, the in vivo results confirmed that this composite hydrogel could significantly promote the defect repair of cranial bone in the rat model. In addition, we also found that ^USCEXOs/GelMA-HAMA/nHAP composite hydrogel can promote the formation of H-type vessels in the bone regeneration area, enhancing the therapeutic effect. In conclusion, our findings suggested that this controllable and biocompatible ^USCEXOs/GelMA-HAMA/nHAP composite hydrogel may effectively promote bone regeneration by coupling osteogenesis and angiogenesis.

Advances and Progress in Self-Healing Hydrogel and Its Application in Regenerative Medicine

A hydrogel is a three-dimensional structure that holds plenty of water, but brittleness largely limits its application. Self-healing hydrogels, a new type of hydrogel that can be repaired by itself after external damage, have exhibited better fatigue resistance, reusability, hydrophilicity, and responsiveness to environmental stimuli. The past decade has seen rapid progress in self-healing hydrogels. Self-healing hydrogels can automatically self-repair after external damage. Different strategies have been proposed, including dynamic covalent bonds and reversible noncovalent interactions. Compared to traditional hydrogels, self-healing gels have better durability, responsiveness, and plasticity. These features allow the hydrogel to survive in harsh environments or even to be injected as a drug carrier. Here, we summarize the common strategies for designing self-healing hydrogels and their potential applications in clinical practice.

Antibacterial brush polypeptide coatings with anionic backbones

Preventing initial colonization of bacteria on biomaterial surfaces is crucial to address the medical device-associated infection issues. Antimicrobial peptide (AMP) or cationic polymer modified surfaces have shown promising potentials to inhibit the initial colonization of bacteria by contact killing. However, their development has been impeded because of bacterial adhesion and high cytotoxicity. Herein, we report a series of brush polypeptide coatings with anionic backbones and cationic AMP mimetic side-chains that displayed superior bactericidal activity, antibacterial adhesion property, and biocompatibility. The cationic side-chain density played an important role in the bioactivities of the brush polypeptide modified surfaces. Brush polypeptide coating with low side-chain density exhibited improved bactericidal activity and antibacterial adhesion property, ascribing to the cooperative effects of adjacent side-chains and backbones/side-chains, respectively. It also showed negligible hemolysis/cytotoxicity in vitro and potent anti-infection property (≥99.9% bactericidal efficacy) in vivo. Brush polymers with anionic backbones and cationic side-chains can be used as a promising design motif to potentiate both antibacterial property and biocompatibility of coatings for combating device-associated infections. STATEMENT OF SIGNIFICANCE: Device-associated infections (DAIs) have led to increased medical cost, pain, and even mortality of patients. Antimicrobial peptide and cationic polymer coatings provide an important strategy to combat DAIs by preventing initial colonization of bacteria on biomaterial surfaces. Nevertheless, they have suffered bacterial adhesion and cytotoxicity issues. Herein, we developed a brush polypeptide coating with anionic backbones and cationic side-chains. The brush polypeptide coating showed superior bactericidal and antibacterial adhesion properties outperforming conventional antibacterial coatings based on antimicrobial peptide (i.e., melittin), lysozyme (i.e., lysostaphin), cationic polymer, anionic polymer, and the blends of cationic/anionic polymers. It also showed good biocompatibility and potent anti-infection property, making it a promising candidate to combat the DAIs.

Dynamic modulation and epoxy functionalization of protein-mediated enoate ester-based hybrid cryogels

The current work is focused on the preparation of protein-mediated poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) copolymer as a self-template for in situ synthesis of hybrid gels. Gelatin, collagen, biotin, and l-arginine were used to create hybrid materials with adjustable swelling and elastic properties. Hybrid cryogels tended to swell more than hybrid hydrogels due to their porous nature. Collaged-doped cryogels had the highest swelling, whereas gelatin-doped hybrids showed enhanced elastic modulus. All hybrid gels exhibited pH-sensitive swelling to controlled release applications depending on the degree of protonation of NH₂ and COOH groups in the side chains. At low pH conditions, hybrid cryogels exhibited a higher swelling tendency compared to hydrogels. Ion-stimulus-response of hybrid gels was studied to evaluate the effect of salt concentration and features of ambient ions on swelling. Depending on the polyelectrolytic or polyampholytic nature, the extent of swelling in NaCl and KCl solutions varied according to the charge distribution in the network chains. Hybrid gels showed excellent adsorption performance for methyl orange by the presence of epoxy, hydroxyl groups, amino and carboxyl groups providing sufficient active sites. Adsorption capacity of hybrid cryogels is higher than that of hydrogels. The removal rate 97/%, reached an equilibrium state in a short period, suggested that collagen-doped hybrid cryogels have a potential application to remove dyestuff from wastewater. In relation to the decrease of methyl orange concentration in solution, adsorption process followed pseudo-second-order kinetic model. Avrami model has provided a better experimental-calculated fit and adsorption thermodynamics analysis indicated that the adsorption was a spontaneous process with a negative standard free energy. The characteristic findings from this research will provide insights into the design and application of enoate-ester and protein-based combinations in the food, biomedical and cosmetic fields.

Nanofibrous hemostatic materials: Structural design, fabrication methods, and hemostatic mechanisms

Development of rapid and effective hemostatic materials has always been the focus of research in the healthcare field. Nanofibrous materials which recapitulate the delicate nano-topography feature of fibrin fibers produced during natural hemostatic process, offer large length-to-diameter ratio and surface area, tunable porous structure, and precise control in architecture, showing great potential for staunching bleeding. Here we present a comprehensive review of advances in nanofibrous hemostatic materials, focusing on the following three important parts: structural design, fabrication methods, and hemostatic mechanisms. This review begins with an introduction to the physiological hemostatic mechanism and current commercial hemostatic agents. Then, it focuses on recent progress in electrospun nanofibrous hemostatic materials in terms of composition and structure control, surface modification, and in-situ deposition. The article emphasizes the development of three-dimensional (3D) electrospun nanofibrous materials and their emerging evolution for improving hemostatic function. Next, it discusses the fabrication of self-assembling peptide or protein-mimetic peptide nanofibers, co-assembling supramolecular nanofibers, as well as other nanofibrous hemostatic agents. Further, the article highlights the external and intracavitary hemostatic management based on various nanofiber aggregates. In the end, this review concludes with the current challenges and future perspectives of nanofibrous hemostatic materials. STATEMENT OF SIGNIFICANCE: This article reviews recent advances in nanofibrous hemostatic materials including fabrication methods, composition and structural control, performance improvement, and hemostatic mechanisms. A variety of methods including electrospinning, self-assembly, grinding and refining, template synthesis, and chemical vapor deposition, have been developed to prepare nanofibrous materials. These methods provide robustness in control of the nanofiber architecture in the forms of hydrogels, two-dimensional (2D) membranes, 3D sponges, or composites, showing promising potential in the external and intracavitary hemostasis and wound healing applications. This review will be of great interest to the broad readers in the field of hemostatic materials and multifunctional biomaterials.

Ultrathin, elastic, and self-adhesive nanofiber bio-tape: An intraoperative drug-loading module for ureteral stents with localized and controlled drug delivery properties for customized therapy

During the postoperative management of urinary diseases, oral or intravenous administration of drugs and implanting ureteral stents are usually required, making localized drug delivery by ureteral stent a precise and effective medication strategy. In the traditional drug loading method, the drug was premixed in the implants in production lines and the versatility of drugs was restricted. However, the complex situation in the urinary system fails the possibility of finding a “one fits all” medication plan, and the intraoperative drug-loading of implants is highly desired to support customized therapy. Here, we designed an ultrathin (8 μm), elastic, and self-adhesive nanofiber bio-tape (NFBT) that can easily encapsulate drugs on the stent surface for controllable localized drug delivery. The NFBT exhibited high binding strength to a ureteral stent, a sustained release over 7 d in PBS for hydrophilic drug, and a zero-order release curve over 28 days for the hydrophobic drug nitrofurantoin (NFT). Further in vivo experiments using a porcine ureteral tract infection model demonstrated that NFBT loaded with NFT could significantly reduce the bacterial concentration in urine. The total amount of NFT delivered by the NFBT was about 2.68 wt% of the recommended dose for the systemic administration.

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An intra operation drug-loading strategy and drug carrier for personalized post-operation management of urinary disease.

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The NFBT is ultrathin (∼8 μm) with enough binding stress to resist displacement bought by ureteral peristalsis.

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In vivo antibacterial rate >99.9% for 28 d (porcine UTI model), with 2.68 wt% of the systemically administration dosage.

Advances of hydrogel combined with stem cells in promoting chronic wound healing

Wounds can be divided into two categories, acute and chronic. Acute wounds heal through the normal wound healing process. However, chronic wounds take longer to heal, leading to inflammation, pain, serious complications, and an economic burden of treatment costs. In addition, diabetes and burns are common causes of chronic wounds that are difficult to treat. The rapid and thorough treatment of chronic wounds, including diabetes wounds and burns, represents a significant unmet medical need. Wound dressings play an essential role in chronic wound treatment. Various biomaterials for wound healing have been developed. Among these, hydrogels are widely used as wound care materials due to their good biocompatibility, moisturizing effect, adhesion, and ductility. Wound healing is a complex process influenced by multiple factors and regulatory mechanisms in which stem cells play an important role. With the deepening of stem cell and regenerative medicine research, chronic wound treatment using stem cells has become an important field in medical research. More importantly, the combination of stem cells and stem cell derivatives with hydrogel is an attractive research topic in hydrogel preparation that offers great potential in chronic wound treatment. This review will illustrate the development and application of advanced stem cell therapy-based hydrogels in chronic wound healing, especially in diabetic wounds and burns.

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.

Self-Assembled Peptide Nanostructures for ECM Biomimicry

Proteins are functional building blocks of living organisms that exert a wide variety of functions, but their synthesis and industrial production can be cumbersome and expensive. By contrast, short peptides are very convenient to prepare at a low cost on a large scale, and their self-assembly into nanostructures and gels is a popular avenue for protein biomimicry. In this Review, we will analyze the last 5-year progress on the incorporation of bioactive motifs into self-assembling peptides to mimic functional proteins of the extracellular matrix (ECM) and guide cell fate inside hydrogel scaffolds.

A hierarchical system of covalent and dual non-covalent crosslinks promotes the toughness and self-healing properties of polymer hydrogels

While it is challenging to simultaneously achieve both high mechanical performance and self-healing ability within one polymer hydrogel network, we, herein, synthesized a novel class of hydrogels based on a combination of chemical and dual non-covalent crosslinks via micellar polymerization of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, end-capped by 2-hydroxyethyl methacrylate (IPDI-HEMA), with acrylamide (AM). The prepared hydrogels were demonstrated to possess a tensile elongation at a break of at least 1900%, a fracture energy of 138.4 kJ m^-3, and remarkable self-healing behaviors (e.g., a strong self-healing ability achieved at ambient temperature without the need for any stimulus or healing agent). The multiple crosslinks developed in this study for one polymer hydrogel network are significant steps to construct the desired functional hydrogels with excellent self-healing and mechanical properties.

Stem cells and common biomaterials in dentistry: a review study

Stem cells exist as normal cells in embryonic and adult tissues. In recent years, scientists have spared efforts to determine the role of stem cells in treating many diseases. Stem cells can self-regenerate and transform into some somatic cells. They would also have a special position in the future in various clinical fields, drug discovery, and other scientific research. Accordingly, the detection of safe and low-cost methods to obtain such cells is one of the main objectives of research. Jaw, face, and mouth tissues are the rich sources of stem cells, which more accessible than other stem cells, so stem cell and tissue engineering treatments in dentistry have received much clinical attention in recent years. This review study examines three essential elements of tissue engineering in dentistry and clinical practice, including stem cells derived from the intra- and extra-oral sources, growth factors, and scaffolds.

Graphene-MoS2 polyfunctional hybrid hydrogels for the healing of transected Achilles tendon

Healing of injured tendon is a major clinical challenge in orthopaedic medicine, due to the poor regenerative potential of this tissue. Two-dimensional nanomaterials, as versatile scaffolds, have shown a great potential to support, trigger and accelerate the tendon regeneration. However, weak mechanical properties, poor functionality and low biocompatibility of these scaffolds as well as post-surgery infections are main drawbacks that limit their development in the higher clinical phases. In this work, a series of hydrogels consisting polyglycerol functionalized reduced graphene oxide (PG), polyglycerol-functionalized molybdenum disulfide (PMoS₂) and PG/PMoS₂ hybrid within the gelatin matrix are formulated in new scaffolds and their ability for the healing of injured Achilles tendon, due to their high mechanical properties, low toxicity, cell proliferation enhancement, and antibacterial activities is investigated. While scaffolds containing PG and PMoS₂ showed a moderate tendon regeneration and anti-inflammatory effect, respectively, their hybridization into PG/PMoS₂ demonstrated a synergistic healing efficiency. Along the same line, an accelerated return of tendon function with low peritendinous adhesion and low cross-sectional area in animal group treated with scaffold containing PG/PMoS₂ was observed. Taking advantage of the high biocompatibility, high strength, straightforward construction and fast tendon regeneration, PG/PMoS₂ can be used as a new scaffold for the future tissue engineering.