Electrospun fiber-based strategies for controlling early innate immune cell responses: Towards immunomodulatory mesh designs that facilitate robust tissue repair

Advances and applications of biomimetic biomaterials for endogenous skin regeneration

Endogenous regeneration is becoming an increasingly important strategy for wound healing as it facilitates skin's own regenerative potential for self-healing, thereby avoiding the risks of immune rejection and exogenous infection. However, currently applied biomaterials for inducing endogenous skin regeneration are simplistic in their structure and function, lacking the ability to accurately mimic the intricate tissue structure and regulate the disordered microenvironment. Novel biomimetic biomaterials with precise structure, chemical composition, and biophysical properties offer a promising avenue for achieving perfect endogenous skin regeneration. Here, we outline the recent advances in biomimetic materials induced endogenous skin regeneration from the aspects of structural and functional mimicry, physiological process regulation, and biophysical property design. Furthermore, novel techniques including in situ reprograming, flexible electronic skin, artificial intelligence, single-cell sequencing, and spatial transcriptomics, which have potential to contribute to the development of biomimetic biomaterials are highlighted. Finally, the prospects and challenges of further research and application of biomimetic biomaterials are discussed. This review provides reference to address the clinical problems of rapid and high-quality skin regeneration.

3D nanofiber scaffolds from 2D electrospun membranes boost cell penetration and positive host response for regenerative medicine

The ideal tissue engineering scaffold should facilitate rapid cell infiltration and provide an optimal immune microenvironment during interactions with the host. Electrospinning can produce two-dimensional (2D) membranes mimicking the extracellular matrix. However, their dense structure hinders cell penetration, and their thin form restricts scaffold utility. In this study, latticed hydrogels were three-dimensional (3D) printed onto electrospun membranes. This technique allowed for layer-by-layer assembly of the membranes into 3D scaffolds, which maintained their resilience impressively under both dry and wet conditions. We assessed the cellular and host responses of these 3D nanofiber scaffolds by comparing random membranes and mesh-like membranes with three different mesh sizes (250, 500, and 750 μm). It was found that scaffolds with a mesh size of 500 μm were superior for M2 macrophage phenotype polarization, vascularization, and matrix deposition. Furthermore, it was confirmed by subsequent experiments such as RNA sequencing that the mesh-like topology may promote polarization to the M2 phenotype by affecting the PI3K/AKT pathway. In conclusion, our work offers a novel method for transforming 2D nanofiber membranes into 3D scaffolds. This method boasts flexibility, allowing for the use of varied electrospun membranes and hydrogels in terms of structure and composition. It has vast potential in tissue repair and regeneration.

Advances and applications of crosslinked electrospun biomacromolecular nanofibers

Electrospinning is a technology for fabricating ultrafine fibers from natural or synthetic polymers that have novel or enhanced functional properties. These fibers have found applications in a diverse range of fields, including the food, medicine, cosmetics, agriculture, and chemical industries. However, the tendency for electrospun nanofibers to dissociate when exposed to certain environmental conditions limits many of their practical applications. The structural integrity and functional attributes of these nanofibers can be improved using physical and/or chemical crosslinking methods. This review article discusses the formation of polymeric nanofibers using electrospinning and then describes how different crosslinking methods can be used to enhance their mechanical, thermal, and biological attributes. Methods for optimizing the crosslinking reactions are discussed, including proper selection of crosslinker type and reaction conditions. Then, food, medical, and separation applications of crosslinked electrospun fibers are assessed, including in bone and skin tissue engineering, wound healing, drug delivery, air filtration, water filtration, oil removal, food packaging, food preservation, and bioactive delivery. Finally, areas where future research are needed are highlighted, as well as possible future applications of crosslinked nanofibers.

Releasable, Immune-Instructive, Bioinspired Multilayer Coating Resists Implant-Induced Fibrosis while Accelerating Tissue Repair

Implantable biomaterials trigger foreign body reactions (FBRs), which reduces the functional life of medical devices and prevents effective tissue regeneration. Although existing therapeutic approaches can circumvent collagen-rich fibrotic encapsulation secondary to FBRs, they disrupt native tissue repair. Herein, a new surface engineering strategy in which an apoptotic-mimetic, immunomodulatory, phosphatidylserine liposome (PSL) is released from an implant coating to induce the formation of a macrophage phenotype that mitigates FBRs and improves tissue healing is described. PSL-multilayers constructed on implant surfaces via the layer-by-layer method release PSLs over a 1-month period. In rat muscles, poly(etheretherketone) (PEEK), a nondegradable polymer implant model, induces FBRs with dense fibrotic scarring under an aberrant cellular profile that recruits high levels of inflammatory infiltrates, foreign body giant cells (FBGCs), scar-forming myofibroblasts, and inflammatory M1-like macrophages but negligible amounts of anti-inflammatory M2-like phenotypes. However, the PSL-multilayer coating markedly diminishes these detrimental signatures by shifting the macrophage phenotype. Unlike other therapeutics, PSL-multilayered coatings also stimulate muscle regeneration. This study demonstrates that PSL-multilayered coatings are effective in eliminating FBRs and promoting regeneration, hence offering potent and broad applications for implantable biomaterials.

Fiber configuration determines foreign body response of electrospun scaffolds:in vitroandin vivoassessments

Biomaterial scaffolds boost tissue repair and regeneration by providing physical support, delivering biological signals and/or cells, and recruiting endogenous cells to facilitate tissue-material integration and remodeling. Foreign body response (FBR), an innate immune response that occurs immediately after biomaterial implantation, is a critical factor in determining the biological outcomes of biomaterial scaffolds. Electrospinning is of great simplicity and cost-effectiveness to produce nanofiber scaffolds with well-defined physicochemical properties and has been used in a variety of regenerative medicine applications in preclinical trials and clinical practice. A deep understanding of causal factors between material properties and FBR of host tissues is beneficial to the optimal design of electrospun scaffolds with favorable immunomodulatory properties. We herein prepared and characterized three electrospun scaffolds with distinct fiber configurations and investigated their effects on FBR in terms of immune cell-material interactions and host responses. Our results show that electrospun yarn scaffold results in greater cellular immune reactions and elevated FBR inin vivoassessments. Although the yarn scaffold showed aligned fiber bundles, it failed to induce cell elongation of macrophages due to its rough surface and porous grooves between yarns. In contrast, the aligned scaffold showed reduced FBR compared to the yarn scaffold, indicating a smooth surface is also a contributor to the immunomodulatory effects of the aligned scaffold. Our study suggests that balanced porousness and smooth surface of aligned fibers or yarns should be the key design parameters of electrospun scaffolds to modulate host responsein vivo.

Graphene quantum dots based on cannabis seeds for efficient wound healing in a mouse incisional wound model: Link with stress and neurobehavioral effect

Graphene quantum dots (GQDs) are promising biomaterials with potential applicability in several areas due to their many useful and unique features. Among different applications, GQDs are photodynamic therapy agents that generate single oxygen and improve antimicrobial activity. In the present study, and for the first time, GQD were isolated from the Cannabis sativa L. seeds to generate C-GQDs as a new biomaterial for antibacterial and wound healing applications. Detailed characterization was performed using FTIR, UV-vis, Raman spectra, photoluminescence, TEM examination, HRTEM, ζ-potential, and XRD. Our results revealed in vitro and in vivo antibacterial activity of C-GQDs against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) with reduced minimal inhibitory concentration of 236 µg/mL for both strains. In addition, the C-GQDs confirmed the in vitro analysis and exhibited anti-inflammatory activity by reducing the level of neutrophils in blood and skin tissue. C-GQDs act by accelerating re-epithelization and granulation tissue formation. In addition, C-GQDs restored neurobehavioral alteration induced by incisional wounds by reducing oxidative stress, decreasing cortisol levels, increasing anxiolytic-like effect, and increasing vertical locomotor activity. The wound-healing effects of C-GQDs support its role as a potential therapeutic agent for diverse skin injuries.

The memory effect of micro/nano-structures activating osteogenic differentiation of BMSCs

Degradable bioceramics such as hydroxyapatite (HA) are usually used as bone grafts due to their excellent osteoconductive ability. Recent studies have proved that decorated micro/nano-structures on HA could enhance its osteogenic capacity by directly activating osteogenic differentiation of bone marrow-derived stem cells (BMSCs) or by indirectly activating the osteoimmune microenvironment. However, it is still unclear whether the degradation process of HA affects the activation effect of micro/nano-structures. In this study, we first demonstrate that the enhanced osteogenic properties activated by micro/nano-structures could be memorized and continue to play a role even after the removal of micro/nano-structures. More interestingly, this topography-triggered osteogenic memory effect (TTOME) could be regulated through the stimulation time, indicating the importance of the rational maintenance of micro/nano-structures as well as the degradation process of bioceramics. These findings provide a perspective of the design of bone implants with a biodegradable surface topography.

Immunomodulatory Biomaterials and Emerging Analytical Techniques for Probing the Immune Micro-Environment

After implantation of a biomaterial, both the host immune system and properties of the material determine the local immune response. Through triggering or modulating the local immune response, materials can be designed towards a desired direction of promoting tissue repair or regeneration. High-throughput sequencing technologies such as single-cell RNA sequencing (scRNA-seq) emerging as a powerful tool for dissecting the immune micro-environment around biomaterials, have not been fully utilized in the field of soft tissue regeneration. In this review, we first discussed the procedures of foreign body reaction in brief. Then, we summarized the influences that physical and chemical modulation of biomaterials have on cell behaviors in the micro-environment. Finally, we discussed the application of scRNA-seq in probing the scaffold immune micro-environment and provided some reference to designing immunomodulatory biomaterials. The foreign body response consists of a series of biological reactions. Immunomodulatory materials regulate immune cell activation and polarization, mediate divergent local immune micro-environments and possess different tissue engineering functions. The manipulation of physical and chemical properties of scaffolds can modulate local immune responses, resulting in different outcomes of fibrosis or tissue regeneration. With the advancement of technology, emerging techniques such as scRNA-seq provide an unprecedented understanding of immune cell heterogeneity and plasticity in a scaffold-induced immune micro-environment at high resolution. The in-depth understanding of the interaction between scaffolds and the host immune system helps to provide clues for the design of biomaterials to optimize regeneration and promote a pro-regenerative local immune micro-environment.