Red blood cell membrane-functionalized Nanofibrous tubes for small-diameter vascular grafts

Hybrid cell membrane coating orchestrates foreign-body reactions, anti-adhesion, and pro-regeneration in abdominal wall reconstruction

Tension-free synthetic meshes are the clinical standard for hernia repair, but they often trigger immune response-mediated complications such as severe foreign-body reactions (FBR), visceral adhesions, and fibrotic healing, increasing the risk of recurrence. Herein, we developed a hybrid cell membrane coating for macroscale mesh fibers that acts as an immune orchestrator, capable of balancing immune responses with tissue regeneration. Cell membranes derived from red blood cells (RBCs) and platelets (PLTs) were covalently bonded to fiber surfaces using functionalized-liposomes and click chemistry. The fusion of clickable liposomes with cell membranes significantly improved coating efficiency, coverage uniformity, and in vivo stability. Histological and flow cytometric analyses of subcutaneous implantation in rats and mice demonstrated significant biofunctional heterogeneity among various cell membrane coatings in FBR. Specifically, the RBC-PLT-liposome hybrid cell membrane coating markedly mitigated FBR, facilitated host cell infiltration, and promoted M2-type macrophage polarization. Importantly, experimental results of abdominal wall defect repairs in rats indicate that the hybrid cell membrane coating effectively prevented visceral adhesions, promoted muscle regenerative healing, and enhanced the recruitment of Pax7+/MyoD+ muscle satellite cells. Our findings suggest that the clickable hybrid cell membrane coating offers a promising approach to enhance clinical outcomes of hernia mesh in abdominal wall reconstruction.

Anticoagulation colloidal microrobots based on heparin-mimicking polymers

Coagulation within blood vessels is a major cause of cardiovascular disease and global mortality, highlighting the urgent need for effective anticoagulant strategies. In this study, we introduce a dynamic and highly efficient anticoagulant platform, achieved through the fabrication of a novel colloidal microrobot with unique functional properties. The microrobot is a Janus colloidal sphere with one hemisphere coated with heparin-mimicking polymers and the other with gold. This structure endows the microrobot with self-propulsion capabilities, powered by biocompatible near-infrared (NIR) irradiation, without the need for chemical fuel. The heparin-mimicking polymers not only prevent blood clotting but also promote endothelial cell growth while inhibiting the proliferation of smooth muscle cells. Additionally, the self-propulsion feature allows the microrobot to travel long distances within blood vessels and precisely target sites for anticoagulation. Our work validates an approach for the production of biofunctionalized microrobots, which introduces a novel avenue for anticoagulation application through the development of innovative biofunctionalized colloidal devices.

Biomimetic nanofibers with cell membrane functionalization for enhanced tissue engineering

Recent advancements in tissue engineering have been driven by the development of nanofibrous scaffolds that replicate key structural and functional features of the natural extracellular matrix. Recently, cell membrane coating technology has emerged as a promising strategy to further enhance the biological functionality of nanofibers by conferring innate cellular recognition, immune evasion, and targeted signaling capabilities. This review aims to provide a comprehensive summary of the recent advancements in the fabrication, characterization, and modification of cell membrane-coated nanofibers for tissue repair. The review commences with an examination of diverse methodologies employed for nanofiber fabrication, encompassing electrospinning, melt electrospinning, and self-assembly techniques. This is followed by an overview of advanced cell membrane extraction methodologies and strategies for stable membrane integration with nanofibers. Subsequently, the review highlights state-of-the-art characterization techniques used to evaluate the physical, chemical, and biological properties of these composite scaffolds. Finally, we address the potential applications of these bioinspired nanofibers in bone regeneration, vascular repair, skin wound healing, and cancer therapy, and provide insights into future perspectives and challenges for clinical translation. Our analysis indicates that cell membrane-coated nanofibers represent a versatile platform for next-generation tissue engineering and regenerative medicine.

Construction of anti-calcification small-diameter vascular grafts using decellularized extracellular matrix/poly (L-lactide-co-ε-caprolactone) and baicalin-cathepsin S inhibitor

The long-term transplantation of small-diameter vascular grafts (SDVGs) is associated with a risk of calcification, which is a key factor limiting the clinical translation of SDVG. Hence, there is an urgency attached to the development of new SDVGs with anti-calcification properties. Here, we used decellularized extracellular matrix (dECM) and poly (L-lactide-co-ε-caprolactone) (PLCL) as base materials and combined these with baicalin, cathepsin S (Cat S) inhibitor to prepare PBC-SDVGs by electrospinning. Baicalin contains carboxyl and hydroxyl groups that can interact with chemical groups in dECM powder, potentially blocking calcium nucleation sites. Cat S inhibitor prevents elastin degradation and further reduces the risk of calcification. PBC-SDVGs were biocompatible and when implanted in rat abdominal aorta, accelerated endothelialization, enhanced vascular tissue regeneration, inhibited elastin degradation, and promoted macrophage polarization M2 phenotype to regulate inflammation. After 3 months of implantation, the results of Doppler ultrasound, MicroCT, and histological staining revealed a significant reduction in calcification. In summary, the developed anti-calcification SDVGs offer a promising strategy for long-term implantation with significant clinical application potential. STATEMENT OF SIGNIFICANCE: The dECM and PLCL were used as base materials, connected with baicalin, and loaded with Cat S inhibitor to prepare PBC-SDVGs. The baicalin and dECM powder formed hydrogen bonds to crosslink together reducing the calcium deposition. In vitro, the vascular graft downregulated the expression level of osteogenic genes and promoted macrophage polarization toward an anti-inflammatory M2 phenotype, thereby reducing calcification. The PBC-SDVGs implanted in rat abdominal aorta can accelerate endothelialization, enhance vascular tissue regeneration, inhibit elastin degradation, reduce inflammation response and calcification.

Engineered Cell Membrane Coating Technologies for Biomedical Applications: From Nanoscale to Macroscale

Cell membrane coating has emerged as a promising strategy for the surface modification of biomaterials with biological membranes, serving as a cloak that can carry more functions. The cloaked biomaterials inherit diverse intrinsic biofunctions derived from different cell sources, including enhanced biocompatibility, immunity evasion, specific targeting capacity, and immune regulation of the regenerative microenvironment. The intrinsic characteristics of biomimicry and biointerfacing have demonstrated the versatility of cell membrane coating technology on a variety of biomaterials, thus, furthering the research into a wide range of biomedical applications and clinical translation. Here, the preparation of cell membrane coatings is emphasized, and different sizes of coated biomaterials from nanoscale to macroscale as well as the engineering strategies to introduce additional biofunctions are summarized. Subsequently, the utilization of biomimetic membrane-cloaked biomaterials in biomedical applications is discussed, including drug delivery, imaging and phototherapy, cancer immunotherapy, anti-infection and detoxification, and implant modification. In conclusion, the latest advancements in clinical and preclinical studies, along with the multiple benefits of cell membrane-coated nanoparticles (NPs) in biomimetic systems, are elucidated.

Rapid Preparation of Collagen/Red Blood Cell Membrane Tubes for Stenosis-Free Vascular Regeneration

Extracellular matrix (ECM)-based small-diameter vascular grafts (SDVGs, inner diameter (ID) < 6 mm) hold great promise for clinical applications. However, existing ECM-based SDVGs suffer from limited donor availability, complex purification, high cost, and insufficient mechanical properties. SDVGs with ECM-like structure and function, and good mechanical properties were rapidly prepared by optimizing common materials and preparation, which can improve their clinical prospects. Here, we rapidly prepared an electrospinning film-collagen/red blood cell membrane-genipin hydrogel tube (ES-C/Rm-G-ht, ID = 2 mm) by the combination of the cross-linking of genipin, plastic compression, electrospinning, and rolling without a biological adhesive, which had a shorter preparation time of less than 17 h compared to the existing ECM-based SDVGs (preparation time of 4-18 weeks). ES-C/Rm-G-ht exhibited a layered honeycomb-like structure and demonstrated the ECM-like functions to promote the proliferation and migration of endothelial cells, and prevent thrombus and inflammation. Furthermore, ES-C/Rm-G-ht, possessing sufficient mechanical strength, showed high patency, rapid endothelialization (95%), good regeneration of smooth muscle cell layers and ECM, and effective antistenosis capability after implantation in the rabbit's carotid artery for 31 days. This work provides a straightforward, cost-effective, and promising strategy to prepare SDVGs with ECM-like structure and function, which is an ideal alternative for vascular grafts and autologous vessels in the current clinic.

Functionalized Iron Oxide Nanoparticles for Both Dual-Modal Imaging and Erythropoiesis

Cancer-related anemia (CRA), a complication of cancer, is considered the primary cause of high mortality for cancer patients. Safe and effective theranostics are desirable for realizing the high diagnostic accuracy of tumors and ameliorating CRA in the clinic. However, the available theranostics do not support dual-modal imaging and the amelioration of CRA at the same time. In this study, we synthesized functionalized iron oxide nanoparticles (Fe3O4 NPs) modified with protoporphyrin IX (PPIX) and folic acid (FA) by a one-step modification strategy (Fe3O4@NH-PPIX&FA NPs) or a step-by-step strategy (Fe3O4@NH-PPIX-FA NPs), aiming at both magnetic resonance imaging/fluorescence imaging (MRI/FI) and erythropoiesis. Fe3O4@NH-PPIX-FA NPs displayed better ability of MRI/FI than Fe3O4@NH-PPIX&FA NPs and had an efficient tumor targeting of 45 min after tail vein injection owing to the reduction of the steric effect and extension of FA groups. Fe3O4@NH-PPIX-FA NPs exhibited satisfactory erythropoiesis with up to 20% elevation of red blood cell (RBC) counts and hemoglobin concentrations in mice with CRA, which provided a safe alternative to RBC transfusions, especially for patients needing recurrent RBC transfusions. With excellent performance in both dual-modal imaging and erythropoiesis, Fe3O4@NH-PPIX-FA NPs could be a powerful tool for the theranostics of cancer patients with anemia.

Vascular Damage and Repair - Are Small-Diameter Vascular Grafts Still the "Holy Grail" of Tissue Engineering?

Cardiovascular diseases are the most important cause of morbidity and mortality in the civilized world. Stenosis or occlusion of blood vessels leads not only to events that are directly life-threatening, such as myocardial infarction or stroke, but also to a significant reduction in quality of life, for example in lower limb ischemia as a consequence of metabolic diseases. The first synthetic polymeric vascular replacements were used clinically in the early 1950s. However, they proved to be suitable only for larger-diameter vessels, where the blood flow prevents the attachment of platelets, pro-inflammatory cells and smooth muscle cells on their inner surface, whereas in smaller-diameter grafts (6 mm or less), these phenomena lead to stenosis and failure of the graft. Moreover, these polymeric vascular replacements, like biological grafts (decellularized or devitalized), are cell-free, i.e. there are no reconstructed physiological layers of the blood vessel wall, i.e. an inner layer of endothelial cells to prevent thrombosis, a middle layer of smooth muscle cells to perform the contractile function, and an outer layer to provide innervation and vascularization of the vessel wall. Vascular substitutes with these cellular components can be constructed by tissue engineering methods. However, it has to be admitted that even about 70 years after the first polymeric vascular prostheses were implanted into human patients, there are still no functional small-diameter vascular grafts on the market. The damage to small-diameter blood vessels has to be addressed by endovascular approaches or by autologous vascular substitutes, which leads to some skepticism about the potential of tissue engineering. However, new possibilities of this approach lie in the use of modern technologies such as 3D bioprinting and/or electrospinning in combination with stem cells and pre-vascularization of tissue-engineered vascular grafts. In this endeavor, sex-related differences in the removal of degradable biomaterials by the cells and in the behavior of stem cells and pre-differentiated vascular cells need to be taken into account. Key words: Blood vessel prosthesis, Regenerative medicine, Stem cells, Footprint-free iPSCs, sr-RNA, Dynamic bioreactor, Sex-related differences.

Antioxidant and Trilayered Electrospun Small-Diameter Vascular Grafts Maintain Patency and Promote Endothelialisation in Rat Femoral Artery

Vascular grafts with a small diameter encounter inadequate patency as a result of intimal hyperplasia development. In the current study, trilayered electrospun small-diameter vascular grafts (PU-PGACL + GA) were fabricated using a poly(glycolic acid) and poly(caprolactone) blend as the middle layer and antioxidant polyurethane with gallic acid as the innermost and outermost layers. The scaffolds exhibited good biocompatibility and mechanical properties, as evidenced by their 6 MPa elastic modulus, 4 N suture retention strength, and 2500 mmHg burst pressure. Additionally, these electrospun grafts attenuated cellular oxidative stress and demonstrated minimal hemolysis (less than 1%). As a proof-of-concept, the preclinical evaluation of the grafts was carried out in the femoral artery of rodents, where the conduits demonstrated satisfactory patency. After 35 days of implantation, ultrasound imaging depicted adequate blood flow through the grafts, and the computed vessel diameter and histological staining showed no significant stenosis issue. Immunohistochemical analysis confirmed matrix deposition (38% collagen I and 16% elastin) and cell infiltration (42% for endothelial cells and 55% for smooth muscle cells) in the explanted grafts. Therefore, PU-PGACL + GA showed characteristics of a clinically relevant small-diameter vascular graft, facilitating re-endothelialization while preserving the anticoagulant properties of the synthetic blood vessels.

Biomimetic tri-layered small-diameter vascular grafts with decellularized extracellular matrix promoting vascular regeneration and inhibiting thrombosis with the salidroside

Small-diameter vascular grafts (SDVGs) are urgently required for clinical applications. Constructing vascular grafts mimicking the defining features of native arteries is a promising strategy. Here, we constructed a tri-layered vascular graft with a native artery decellularized extracellular matrix (dECM) mimicking the component of arteries. The porcine thoracic aorta was decellularized and milled into dECM powders from the differential layers. The intima and media dECM powders were blended with poly (L-lactide-co-caprolactone) (PLCL) as the inner and middle layers of electrospun vascular grafts, respectively. Pure PLCL was electrospun as a strengthening sheath for the outer layer. Salidroside was loaded into the inner layer of vascular grafts to inhibit thrombus formation. In vitro studies demonstrated that dECM provided a bioactive milieu for human umbilical vein endothelial cell (HUVEC) extension adhesion, proliferation, migration, and tube-forming. The in vivo studies showed that the addition of dECM could promote endothelialization, smooth muscle regeneration, and extracellular matrix deposition. The salidroside could inhibit thrombosis. Our study mimicked the component of the native artery and combined it with the advantages of synthetic polymer and dECM which provided a promising strategy for the design and construction of SDVGs.