Endogenous Stem Cell-Based In Situ Tissue Regeneration Using Electrostatically Interactive Hydrogel with a Newly Discovered Substance P Analog and VEGF-Mimicking Peptide

Metal element-fusion peptide heterostructured nanocoatings endow polyetheretherketone implants with robust anti-bacterial activities and in vivo osseointegration

Polyetheretherketone (PEEK), renowned for its exceptional mechanical properties and bio-stability, is considered a promising alternative to traditional metal-based implants. However, the inferior bactericidal activity and the limited angiogenic and osteogenic properties of PEEK remain the three major obstacles to osseointegration in vivo. To overcome these obstacles, in this work, a versatile heterostructured nanocoating was conceived and equipped on PEEK. This nanocoating was designed to endow PEEK with the ability of photo-activated pathogen disinfection, along with enhanced angiogenesis and osteogenesis, effectively addressing the triple-barrier challenge towards osseointegration. The crafted nanocoating, encompassing diverse nutritional metal elements (Fe3+, Mg2+, and Sr2+) and a fusion peptide adept at promoting angiogenesis and osteogenesis, was seamlessly decorated onto PEEK. The engineered implant exhibited an antibacterial activity of over 94% upon near-infrared illumination by virtue of the photothermal conversion of the polyphenol nanocoating. Simultaneously, the decorated hierarchical nanocoatings synergistically promoted cellular adhesion and proliferation and up-regulated angiogenesis-/osteogenesis-associated cytokine expression in endothelial/osteoblast cells, resulting in superior angiogenic differentiation and osteoinductive capability in vitro. Moreover, an in vivo assay in a rabbit femoral defect model revealed that the decorated implant can achieve ameliorative osseointegrative fixation. Collectively, this work offers a practical and instructive clinical strategy to address the triple-barrier challenge associated with PEEK-based implants.

Drop to Gate Nasal Drops Attenuates Sepsis-Induced Cognitive Dysfunction

Nasal administration can bypass the blood-brain barrier and directly deliver drugs to the brain, providing a non-invasive route for central nervous system (CNS) diseases. Inspired by the appearance that a gate can block the outside world and the characteristics of the sol-gel transition can form a "gate" in the nasal cavity, a Drop to Gate nasal drop (DGND) is designed to set a gate in nose, which achieves protecting role from the influence of nasal environment. The DGND demonstrates the efficiency and application prospect of delivering drugs to the brain through the N-to-B. The effective concentration of single administration is increased through the hydrophobic interaction between C8-GelMA and SRT1720 (SA), and then cross-linked under UV to form nanogel, which can respond to MMP in the inflammatory microenvironment of sepsis-induced cognitive dysfunction. Finally, the SA/nanogel is compounded into the thermogel, which can respond to the nasal cavity temperature to form DGND in situ, increasing the residence time and delivery efficiency of drugs in the nasal cavity. In vitro, the DGND alleviates lipopolysaccharides (LPS)-induced BV2 inflammation. In vivo, DGND effectively targets the nasal mucosa and deliver drugs to the brain, which activate Sirt1 to alleviate inflammation mediated by microglia and improve cognitive dysfunction in sepsis mice.

A Photo-induced Cross-Linking Enhanced A and B Combined Multi-Functional Spray Hydrogel Instantly Protects and Promotes of Irregular Dynamic Wound Healing

Wounds in harsh environments can face long-term inflammation and persistent infection, which can slow healing. Wound spray is a product that can be rapidly applied to large and irregularly dynamic wounds, and can quickly form a protective film in situ to inhibit external environmental infection. In this study, a biodegradable A and B combined multi-functional spray hydrogel is developed with methacrylate-modified chitosan (CSMA1st) and ferulic acid (FA) as type A raw materials and oxidized Bletilla striata polysaccharide (OBSP) as type B raw materials. The precursor CSMA1st-FA/OBSP (CSOB-FA1st) hydrogel is formed by the self-cross-linking of dynamic Schiff base bonds, the CSMA-FA/OBSP (CSOB-FA) hydrogel is formed quickly after UV-vis light, so that the hydrogel fits with the wound. Rapid spraying and curing provide sufficient flexibility and rapidity for wounds and the hydrogel has good injectability, adhesive, and mechanical strength. In rats and miniature pigs, the A and B combined spray hydrogel can shrink wounds and promote healing of infected wounds, and promote the enrichment of fibrocyte populations. Therefore, the multifunctional spray hydrogel combined with A and B can protect irregular dynamic wounds, prevent wound infection and secondary injury, and be used for safe and effective wound treatment, which has a good prospect for development.

Oxygen generating biomaterials at the forefront of regenerative medicine: advances in bone regeneration

Globally, an annual count of more than two million bone transplants is conducted, with conventional treatments, including metallic implants and bone grafts, exhibiting certain limitations. In recent years, there have been significant advancements in the field of bone regeneration. Oxygen tension regulates cellular behavior, which in turn affects tissue regeneration through metabolic programming. Biomaterials with oxygen release capabilities enhance therapeutic effectiveness and reduce tissue damage from hypoxia. However, precise control over oxygen release is a significant technical challenge, despite its potential to support cellular viability and differentiation. The matrices often used to repair large-size bone defects do not supply enough oxygen to the stem cells being used in the regeneration process. Hypoxia-induced necrosis primarily occurs in the central regions of large matrices due to inadequate provision of oxygen and nutrients by the surrounding vasculature of the host tissues. Oxygen generating biomaterials (OGBs) are becoming increasingly significant in enhancing our capacity to facilitate the bone regeneration, thereby addressing the challenges posed by hypoxia or inadequate vascularization. Herein, we discussed the key role of oxygen in bone regeneration, various oxygen source materials and their mechanism of oxygen release, the fabrication techniques employed for oxygen-releasing matrices, and novel emerging approaches for oxygen delivery that hold promise for their potential application in the field of bone regeneration.

In-situ wound healing by SDF-1-mimic peptide-loaded click crosslinked hyaluronic acid scaffold

Endogenous stem cell-based in-situ tissue regeneration has recently gained considerable attention. In this study, we investigated the potential of a chemokine, SDF-1-mimic peptide (SMP), to promote endogenous stem cell-based in-situ wound healing. Our approach involved the development of a click crosslinked hyaluronic acid scaffold loaded with SMP (Cx-HA + SMP) to release SMP in a wound site. The Cx-HA scaffold maintained its structural integrity throughout the wound healing process and also captured endogenous stem cells. Gradual SMP release from the Cx-HA + SMP scaffold established a concentration gradient at the wound site. In animal wound experiments, Cx-HA + SMP exhibited faster wound contraction compared to Cx-HA + SDF-1. Additionally, Cx-HA + SMP resulted in approximately 1.2-1.6 times higher collagen formation compared to Cx-HA + SDF-1. SMP released from the Cx-HA + SMP scaffold promoted endogenous stem cell migration to the wound site 1.5 times more effectively than Cx-HA + SDF-1. Moreover, compared to Cx-HA + SDF-1, Cx-HA + SMP exhibited higher expression of CXCR4 and CD31, as well as the positive markers CD29 and CD44 for endogenous stem cells. The endogenous stem cells that migrated through Cx-HA + SMP regenerated into wound skin with minimal scar granule formation, similar to the normal tissue. In conclusion, SMP peptide offers greater convenience, while efficiently attracting migrating endogenous stem cells compared to the SDF protein. Our findings suggest that Cx-HA + SMP scaffolds hold promise as a strategy to enhance endogenous stem cell-based in-situ wound healing.

Preparation and Properties of Self-Cross-Linking Hydrogels Based on Chitosan Derivatives and Oxidized Sodium Alginate

A self-cross-linking and biocompatible hydrogel has wide application potential in the field of tissue engineering. In this work, an easily available, biodegradable, and resilient hydrogel was prepared using a self-cross-linking method. This hydrogel was composed of N-2-hydroxypropyl trimethyl ammonium chloride chitosan (HACC) and oxidized sodium alginate (OSA). A stable and reversible cross-linking network was formed by the Schiff base self-cross-linked and hydrogen bonding. The addition of a shielding agent (NaCl) may weaken the intense electrostatic effect between HACC and OSA and solve the problem of flocculation caused by the rapid formation of ionic bonds, which provided an extended time for the Schiff base self-cross-linked reaction for forming a homogeneous hydrogel. Interestingly, the shortest time for the formation of the HACC/OSA hydrogel was within 74 s and the hydrogel had a uniform porous structure and enhanced mechanical properties. The HACC/OSA hydrogel withstood large compression deformation due to improved elasticity. What's more, this hydrogel possessed favorable swelling property, biodegradation, and water retention. The HACC/OSA hydrogels have great antibacterial properties against Staphylococcus aureus and Escherichia coli and demonstrated good cytocompatibility as well. The HACC/OSA hydrogels have a good sustained release effect on rhodamine (model drug). Thus, the obtained self-cross-linked HACC/OSA hydrogels in this study have potential applications in the field of biomedical carriers.

Injectable In Situ Photocrosslinked Hydrogel Dressing for Infected Wound Healing

A traditional injectable photocrosslinked hydrogel had disadvantages of the residual photoinitiator and toxic crosslinker, slow in situ curing, and a complex preparation process. At the same time, hydrogels cannot act as artificial skin to restore skin sensory function during the wound healing cycle. In this work, an injectable photocrosslinked hydrogel was prepared which can be quickly in situ cured without photoinitiator. Oxidized sodium alginate was used as a natural macromolecular crosslinking agent to form an injectable hydrogel framework with the photosensitive polymer polyvinyl alcohol bearing styrylpyridinium group (PVA-SBQ). In addition, the hydrogel was endowed with photothermal therapy property after the introduction of biomass-like polydopamine particles. When used as a wound dressing, the hydrogel exhibited an excellent antibacterial property, with an antibacterial rate of 99.56% Escherichia coli and 97.96% Staphylococcus aureus. As a result, the hydrogel could significantly accelerate the repair of infected wounds, with a wound healing rate of 96.45% after 14 days. Moreover, the hydrogel exhibited a sensitive and stable sensing property, making it promising to reconstitute the sensory function of damaged skin during treatment. This work provides an idea for the development of injectable photocrosslinked hydrogel dressing.

Combined effect of SDF-1 peptide and angiogenic cues in co-axial PLGA/gelatin fibers for cutaneous wound healing in diabetic rats

Skin regeneration is hindered by poor vascularization, prolonged inflammation, and excessive scar tissue formation, which necessitate newer strategies to simultaneously induce blood vessel regeneration, resolve inflammation, and induce host cell recruitment. Concurrent deployment of multiple biological cues to realize synergistic reparative effects may be an enticing avenue for wound healing. Herein, we simultaneously deployed SDF (stromal cell-derived factor)- 1α, VEGF (vascular endothelial growth factor)-binding peptide (BP), and GLP (glucagon like peptide)- 1 analog, liraglutide (LG) in core/shell poly(L-lactide-co-glycolide)/gelatin fibers to harness their synergistic effects for skin repair in healthy as well as diabetic wound models in rats. Microscopic techniques, such as SEM and TEM revealed fibrous and core/shell type morphology of membranes. Boyden chamber assay and scratch-wound assay displayed significant migration of HUVECs (human umbilical vein endothelial cells) in SDF-1α containing fibers. Subcutaneous implantation of membranes revealed higher cellular infiltration in SDF-1α loaded fibers, especially, those which were co-loaded with LG or BP. Implantation of membranes in an excisional wound model in healthy rats further showed significant and rapid wound closure in dual cues loaded groups as compared to control or single cue loaded groups. Similarly, the implantation of dressings in type 2 diabetes rat model revealed fast healing, skin appendages regeneration, and blood vessel regeneration in dual cues loaded fibers (SDF-1α/LG, SDF-1α/BP). Taken together, core/shell type fibers containing bioactive peptides significantly promoted wound repair in healthy as well as diabetic wound models in rats.

Efficacy Evaluation of SDF-1α-Based Polypeptides in an Acute Myocardial Infarction Model Using Structure-Based Drug Design

Stromal cell-derived factor-1 alpha (SDF-1α, CXCL12) mediates the migration of circulating cells to desired sites for tissue development, homeostasis, and regeneration and can be used to promote cardiac regeneration by recruiting stem cells. However, the use of SDF-1α in the injured heart necessitates not only higher binding affinity to its receptor, CXCR4+, but also better robustness against enzymatic degradation than other SDF-1 isoforms. Here, we conduct a screening of SDF-1α analog peptides that were designed by structure-based drug design (SBDD), a type of computer-aided drug design (CADD). We have developed in vitro and in vivo methods that enable us to estimate the effect of peptides on the migration of human mesenchymal stem cells (hMSCs) and cardiac regeneration in acute myocardial infarction (AMI)-induced animals, respectively. We demonstrate that one type of SDF-1α analog peptide, SDP-4, among the four analog peptides preselected by SBDD, is more potent than native SDF-1α for cardiac regeneration in myocardial infarction. It is interesting to note that the migratory effects of SDP-4 determined by a wound healing assay, a Transwell assay, and a 2D migration assay are comparable to those of SDF-1α. These results suggest that in vivo, as well as in vitro, screening of peptides developed by SBDD is a quintessential process to the development of a novel therapeutic compound for cardiac regeneration. Our finding also has an implication that the SDP-4 peptide is an excellent candidate for use in the regeneration of an AMI heart.

Progress of Research in In Situ Smart Hydrogels for Local Antitumor Therapy: A Review

Cancer seriously threatens human health. Surgery, radiotherapy and chemotherapy are the three pillars of traditional cancer treatment, with targeted therapy and immunotherapy emerging over recent decades. Standard drug regimens are mostly executed via intravenous injection (IV), especially for chemotherapy agents. However, these treatments pose severe risks, including off-target toxic side effects, low drug accumulation and penetration at the tumor site, repeated administration, etc., leading to inadequate treatment and failure to meet patients’ needs. Arising from these challenges, a local regional anticancer strategy has been proposed to enhance therapeutic efficacy and concomitantly reduce systemic toxicity. With the advances in biomaterials and our understanding of the tumor microenvironment, in situ stimulus-responsive hydrogels, also called smart hydrogels, have been extensively investigated for local anticancer therapy due to their injectability, compatibility and responsiveness to various stimuli (pH, enzyme, heat, light, magnetic fields, electric fields etc.). Herein, we focus on the latest progress regarding various stimuli that cause phase transition and drug release from smart hydrogels in local regional anticancer therapy. Additionally, the challenges and future trends of the reviewed in situ smart hydrogels for local drug delivery are summarized and proposed.

Mussel Inspired Trigger-Detachable Adhesive Hydrogel

Adhesion to many kinds of surfaces, including biological tissues, is important in many fields but has been proved to be extremely challenging. Furthermore, peeling from strong adhesion is needed in many conditions, but is sometimes painful. Herein, a mussel inspired hydrogel is developed to achieve both strong adhesion and trigger-detachment. The former is actualized by electrostatic interactions, covalent bonds, and physical interpenetration, while the latter is triggered, on-demand, through combining a thixotropic supramolecular network and polymer double network. The results of the experiments show that the hydrogel can adhere to various material surfaces and tissues. Moreover, triggered by shear force, non-covalent interactions of the supramolecular network are destroyed. This adhesion can be peeled easily. The possible mechanism involved is discussed and proved. This work will bring new insight into electronic engineering and tissue repair like skin care for premature infants and burn victims.