Advanced Immunomodulatory Biomaterials for Therapeutic Applications

The multifaceted biological defense system modulating complex immune responses against pathogens and foreign materials plays a critical role in tissue homeostasis and disease progression. Recently developed biomaterials that can specifically regulate immune responses, nanoparticles, graphene, and functional hydrogels have contributed to the advancement of tissue engineering as well as disease treatment. The interaction between innate and adaptive immunity, collectively determining immune responses, can be regulated by mechanobiological recognition and adaptation of immune cells to the extracellular microenvironment. Therefore, applying immunomodulation to tissue regeneration and cancer therapy involves manipulating the properties of biomaterials by tailoring their composition in the context of the immune system. This review provides a comprehensive overview of how the physicochemical attributes of biomaterials determine immune responses, focusing on the physical properties that influence innate and adaptive immunity. This review also underscores the critical aspect of biomaterial-based immune engineering for the development of novel therapeutics and emphasizes the importance of understanding the biomaterials-mediated immunological mechanisms and their role in modulating the immune system.

Adipose-derived stem cells derived decellularized extracellular matrix enabled skin regeneration and remodeling

The tissues or organs derived decellularized extracellular matrix carry immunogenicity and the risk of pathogen transmission, resulting in limited therapeutic effects. The cell derived dECM cultured in vitro can address these potential risks, but its impact on wound remodeling is still unclear. This study aimed to explore the role of decellularized extracellular matrix (dECM) extracted from adipose derived stem cells (ADSCs) in skin regeneration. Methods: ADSCs were extracted from human adipose tissue. Then we cultivated adipose-derived stem cell cells and decellularized ADSC-dECM for freeze-drying. Western blot (WB), enzyme-linked immunosorbent assay (ELISA) and mass spectrometry (MS) were conducted to analyzed the main protein components in ADSC-dECM. The cell counting assay (CCK-8) and scratch assay were used to explore the effects of different concentrations of ADSC-dECM on the proliferation and migration of human keratinocytes cells (HaCaT), human umbilical vein endothelia cells (HUVEC) and human fibroblasts (HFB), respectively. Moreover, we designed a novel ADSC-dECM-CMC patch which used carboxymethylcellulose (CMC) to load with ADSC-dECM; and we further investigated its effect on a mouse full thickness skin wound model. Results: ADSC-dECM was obtained after decellularization of in vitro cultured human ADSCs. Western blot, ELISA and mass spectrometry results showed that ADSC-dECM contained various bioactive molecules, including collagen, elastin, laminin, and various growth factors. CCK-8 and scratch assay showed that ADSC-dECM treatment could significantly promote the proliferation and migration of HaCaT, human umbilical vein endothelia cells, and human fibroblasts, respectively. To evaluate the therapeutic effect on wound healing in vivo, we developed a novel ADSC-dECM-CMC patch and transplanted it into a mouse full-thickness skin wound model. And we found that ADSC-dECM-CMC patch treatment significantly accelerated the wound closure with time. Further histology and immunohistochemistry indicated that ADSC-dECM-CMC patch could promote tissue regeneration, as confirmed via enhanced angiogenesis and high cell proliferative activity. Conclusion: In this study, we developed a novel ADSC-dECM-CMC patch containing multiple bioactive molecules and exhibiting good biocompatibility for skin reconstruction and regeneration. This patch provides a new approach for the use of adipose stem cells in skin tissue engineering.

Lentinan-functionalized graphene oxide hydrogel as a sustained antigen delivery system for vaccines

Hydrogel has been proven to have the ability to deliver antigens continuously to achieve slow vaccine delivery, which makes it a promising candidate for an adjuvant delivery platform. Meanwhile, graphene oxide (GO) has garnered significant attention due to its good biosafety, excellent surface area and easy modification. However, GO exists as weak colloidal particles and poses challenges in self-assembling into a hydrogel structure. Here, we propose an innovative strategy involving self-assembling lentinan-functionalized graphene oxide hydrogel ((LNT-GO Gel) by simply mixing lentinan (LNT)-functionalized GO with polyethylene imide (PEI), which can simultaneously encapsulate antigens, achieve long-lasting release of antigens and generate excellent adjuvant activity. The results indicated that the LNT-GO Gel can control the release of OVA at the injection site and confer targeted delivering capacity to lymph nodes. And the date demonstrates that LNT-GO Gel displays favorable safety and biodegradability in vivo. Moreover, LNT-GO Gel can enhance the activation and maturation of dendritic cells (DCs) in lymph node, induce stronger OVA-specific antibody response, and promote spleen T lymphocyte differentiation, which underscores that LNT-GO Gel has ability to generate stronger antigen-specific humoral and cellular immune responses. Collectively, these results demonstrate the adjuvant potential of the lentinan-functionalized graphene oxide hydrogel (LNT-GO Gel) for subunit vaccine.

Layer-by-Layer Analysis of In Vitro Skin Models

In vitro human skin models are evolving into versatile platforms for the study of skin biology and disorders. These models have many potential applications in the fields of drug testing and safety assessment, as well as cosmetic and new treatment development. The development of in vitro skin models that accurately mimic native human skin can reduce reliance on animal models and also allow for more precise, clinically relevant testing. Recent advances in biofabrication techniques and biomaterials have led to the creation of increasingly complex, multilayered skin models that incorporate important functional components of skin, such as the skin barrier, mechanical properties, pigmentation, vasculature, hair follicles, glands, and subcutaneous layer. This improved ability to recapitulate the functional aspects of native skin enhances the ability to model the behavior and response of native human skin, as the complex interplay of cell-to-cell and cell-to-material interactions are incorporated. In this review, we summarize the recent developments in in vitro skin models, with a focus on their applications, limitations, and future directions.

Extracellular matrix-mimetic electrically conductive nanofibrous scaffolds based on polyaniline-grafted tragacanth gum and poly(vinyl alcohol) for skin tissue engineering application

As pivotal role of scaffold in tissue engineering (TE), the aim of present study was to design and development of extracellular matrix (ECM)-mimetic electrically conductive nanofibrous scaffolds composed of polyaniline-grafted tragacanth gum (TG-g-PANI) and poly(vinyl alcohol) (PVA) with different PANI content for skin tissue engineering (STE) application. The fabricated scaffolds were preliminary evaluated in terms of some physicochemical and biological properties. Cytocompatibility and cells proliferation properties of the scaffolds were examined with the well-known MTT assay, and it was found that the developed scaffolds have proper cytocompatibilities and can enhances the mouse fibroblast L929 cells adhesion as well as proliferation, which confirm their potential for STE applications. Hemocompatibility assay revealed that the hemolysis rate of the fabricated scaffolds were <2 % even at a relatively high concentration (200 μgmL-1) of samples, therefore, these scaffolds can be considered as safe. Human serum albumin (HSA) protein adsorption capacities of the fabricated scaffolds were quantified as 42 and 49 μgmg-1 that represent suitable values for a successful TE. Overall, the fabricated scaffold with 20 wt% of TG-g-PANI showed higher potential in both physicochemical and biological features than scaffold with 30 wt% of mentioned copolymer for STE application.

Nanomaterials supported by polymers for tissue engineering applications: A review

In the biomedical sciences, particularly in wound healing, tissue engineering, and regenerative medicine, the development of natural-based biomaterials as a carrier has revealed a wide range of advantages. Tissue engineering is one of the therapeutic approaches used to replace damaged tissue. Polymers have received a lot of attention for their beneficial interactions with cells, but they have some drawbacks, such as poor mechanical properties. Due to their relatively large surface area, nanoparticles can cause significant changes in polymers and improve their mechanical properties. The nanoparticles incorporated into biomaterial scaffolds have been associated with positive effects on cell adhesion, viability, proliferation, and migration in the majority of studies. This review paper discusses recent applications of polymer-nanoparticle composites in the development of tissue engineering scaffolds, as well as the effects of these nanomaterials in the fields of cardiovascular, neural, bone, and skin tissue engineering.

Graphene oxide accelerates diabetic wound repair by inhibiting apoptosis of Ad-MSCs via Linc00324/miR-7977/STK4 pathway

Many studies have shown that graphene oxide (GO) promotes proliferation and differentiation of a variety of stem cells. However, its effect on adipose-derived mesenchymal stem cell (Ad-MSCs) apoptosis is still unclear. Apoptosis is a significant factor affecting stem cell-based treatment of diabetic wounds. Therefore, we explored the effect of GO on Ad-MSC apoptosis and diabetic wound healing. In this study, qRT-PCR was used to detect Ad-MSC expression of LncRNAs, miRNAs, and mRNAs under high-glucose environment. RNA immunoprecipitation (RIP), RNA pull-down, and luciferase assays were used to detect interactions of specific lncRNAs, miRNAs, and mRNAs. The effects of GO on Ad-MSC apoptosis were explored by flow cytometry, TUNEL assay, and Western blot. A diabetic wound model was used to explore the function of Linc00324 on Ad-MSC reparative properties in vivo. As a result, GO inhibited high glucose-induced apoptosis in Ad-MSCs, and Linc00324 contributed to the anti-apoptotic effect of GO. RIP and RNA pull-down confirmed that Linc00324 directly interacted with miR-7977, functioning as a miRNA sponge to regulate expression of the miR-7977 target gene STK4 (MST1) and downstream signaling pathways. In addition, GO reduced the apoptosis of Ad-MSCs in wounds and promoted wound healing. Taken together, these findings suggest GO may be a superior auxiliary material for Ad-MSCs to facilitate diabetic wound healing via the Linc00324/miR-7977/STK4 pathway.

An Update on Graphene Oxide: Applications and Toxicity

Graphene oxide (GO) has attracted much attention in the past few years because of its interesting and promising electrical, thermal, mechanical, and structural properties. These properties can be altered, as GO can be readily functionalized. Brodie synthesized the GO in 1859 by reacting graphite with KClO3 in the presence of fuming HNO3; the reaction took 3-4 days to complete at 333 K. Since then, various schemes have been developed to reduce the reaction time, increase the yield, and minimize the release of toxic byproducts (NO2 and N2O4). The modified Hummers method has been widely accepted to produce GO in bulk. Due to its versatile characteristics, GO has a wide range of applications in different fields like tissue engineering, photocatalysis, catalysis, and biomedical applications. Its porous structure is considered appropriate for tissue and organ regeneration. Various branches of tissue engineering are being extensively explored, such as bone, neural, dentistry, cartilage, and skin tissue engineering. The band gap of GO can be easily tuned, and therefore it has a wide range of photocatalytic applications as well: the degradation of organic contaminants, hydrogen generation, and CO2 reduction, etc. GO could be a potential nanocarrier in drug delivery systems, gene delivery, biological sensing, and antibacterial nanocomposites due to its large surface area and high density, as it is highly functionalized with oxygen-containing functional groups. GO or its composites are found to be toxic to various biological species and as also discussed in this review. It has been observed that superoxide dismutase (SOD) and reactive oxygen species (ROS) levels gradually increase over a period after GO is introduced in the biological systems. Hence, GO at specific concentrations is toxic for various species like earthworms, Chironomus riparius, Zebrafish, etc.

Chondrogenic potential of manganese-loaded composite scaffold combined with chondrocytes for articular cartilage defect

Cartilage is an alymphatic, avascular and non-innervated tissue. Lack of potential regenerative capacity to reconstruct chondral defect has accelerated investigation and development of new strategy for cartilage repair. We prepared a manganese ion-incorporated natupolymer-based scaffold with chitosan-gelatin by freeze-drying procedure. The scaffold was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, energy dispersive spectroscopy, compressive testing, and analysis of porosity and flexibility. Live/dead assay confirmed the good cytocompatibility of prepared scaffold on rat articular chondrocytes after 10 days and 4 weeks of culture. The manganese-loaded composite scaffold upregulated the expression of chondrogenic-related markers (Sox9, integrin, and Col II) in chondrocytes. Western blot analysis of proteins extracted from chondrocytes grown on scaffolds indicated the signaling pathways of p-Akt and p-ERK1/2 played a key role. Histological analysis following implantation of current composite scaffold loaded with chondrocytes into a rat articular cartilage defect model showed that the scaffolds promoted the formation of collagen II and cartilage repair. These findings suggested the potential of manganese-loaded scaffold to promote new cartilage formation and a promising strategy for articular cartilage engineering application.

Antibacterial performance of graphene oxide/alginate-based antisense hydrogel for potential therapeutic application in Staphylococcus aureus infection

Staphylococcus aureus (S. aureus) is an opportunistic bacterium that causes several infections in humans. However, chronic biofilms remain a major challenge associated with recalcitrance toward traditional treatments. Herein, an antibacterial hydrogel composed of antisense DNA oligonucleotides, graphene oxide and alginate is construed for biofilm management and infection care. The hydrogel is established through noncovalent binding and possesses injectability and degradability properties. Furthermore, hydrogels present controllable release of cargoes, genetic targeting antibacterial effects and stem cell supporting capabilities. Our in vivo results reveal a high antibiofilm performance and good biocompatibility, which significantly improve tissue regeneration. The hydrogel inhibits biofilm formation by decreasing the expression of YycFG with antisense and viability of strains by graphene oxide. Thus, antisense hydrogels can be a promising antibacterial bioactive material for potential therapeutic S. aureus infection.

VEGF loaded porcine decellularized adipose tissue derived hydrogel could enhance angiogenesis in vitro and in vivo

Decellularized adipose tissue (DAT) has been widely applied in soft tissue regeneration, however, DAT may play a promising role in accelerating wound healing because of suitable physical characteristics and biological properties. In this research, we fabricated the DAT hydrogel and the VEGF loaded heparinized-DAT hydrogel (VEGF hydrogel) and evaluated their efficiency in full-thickness skin wound model. We designed one method to encapsulate VEGF to hep-DAT hydrogel in order to control VEGF release rate. Result showed that the VEGF release could last up to 3 day, and 1 ml hep-DAT hydrogel (5 mg/ml) could bind up to (64.521 ± 11.550) ng VEGF which was 4.2 times to that of DAT hydrogels. Moreover, the VEGF released in 3 days still preserved biological activities that the released VEGF could enhance tube formation of HUVECs in vitro. Otherwise, the VEGF hydrogel could significantly accelerate wound healing compared with DAT hydrogel and VEGF injection, collagen deposition and newly formed vessels in the VEGF hydrogel groups were also higher than those of other groups. We believed that the VEGF hydrogel could be one attractive biomaterial for potential clinical applications.

Cell-derived extracellular matrix materials for tissue engineering

The involvement of cell-derived extracellular matrix (CDM) in assembling tissue engineering scaffolds has yielded significant results. CDM possesses excellent characteristics, such as ideal cellular microenvironment mimicry and good biocompatibility, which make it a popular research direction in the field of bionanomaterials. CDM has significant advantages as an expansion culture substrate for stem cells, including stabilization of phenotype, reversal of senescence, and guidance of specific differentiation. In addition, the applications of CDM-assembled tissue engineering scaffolds for disease simulation and tissue organ repair are comprehensively summarized; the focus is mainly on bone and cartilage repair, skin defect or wound healing, engineered blood vessels, peripheral nerves, and periodontal tissue repair. We consider CDM a highly promising bionic biomaterial for tissue engineering applications and propose a vision for its comprehensive development.

A Critical Review on Polymeric Biomaterials for Biomedical Applications

Natural and synthetic polymers have been explored for many years in the field of tissue engineering and regeneration. Researchers have developed many new strategies to design successful advanced polymeric biomaterials. In this review, we summarized the recent notable advancements in the preparation of smart polymeric biomaterials with self-healing and shape memory properties. We also discussed novel approaches used to develop different forms of polymeric biomaterials such as films, hydrogels and 3D printable biomaterials. In each part, the applications of the biomaterials in soft and hard tissue engineering with their in vitro and in vivo effects are underlined. The future direction of the polymeric biomaterials that could pave a path towards successful clinical implications is also underlined in this review.

Redox Polymers for Tissue Engineering

This review will focus on the targeted design, synthesis and application of redox polymers for use in regenerative medicine and tissue engineering. We define redox polymers to encompass a variety of polymeric materials, from the multifunctional conjugated conducting polymers to graphene and its derivatives, and have been adopted for use in the engineering of several types of stimulus responsive tissues. We will review the fundamental properties of organic conducting polymers (OCPs) and graphene, and how their properties are being tailored to enhance material - biological interfacing. We will highlight the recent development of high-resolution 3D fabrication processes suitable for biomaterials, and how the fabrication of intricate scaffolds at biologically relevant scales is providing exciting opportunities for the application of redox polymers for both in-vitro and in-vivo tissue engineering. We will discuss the application of OCPs in the controlled delivery of bioactive compounds, and the electrical and mechanical stimulation of cells to drive behaviour and processes towards the generation of specific functional tissue. We will highlight the relatively recent advances in the use of graphene and the exploitation of its physicochemical and electrical properties in tissue engineering. Finally, we will look forward at the future of organic conductors in tissue engineering applications, and where the combination of materials development and fabrication processes will next unite to provide future breakthroughs.

Graphene Oxide: Opportunities and Challenges in Biomedicine

Desirable carbon allotropes such as graphene oxide (GO) have entered the field with several biomedical applications, owing to their exceptional physicochemical and biological features, including extreme strength, found to be 200 times stronger than steel; remarkable light weight; large surface-to-volume ratio; chemical stability; unparalleled thermal and electrical conductivity; and enhanced cell adhesion, proliferation, and differentiation properties. The presence of functional groups on graphene oxide (GO) enhances further interactions with other molecules. Therefore, recent studies have focused on GO-based materials (GOBMs) rather than graphene. The aim of this research was to highlight the physicochemical and biological properties of GOBMs, especially their significance to biomedical applications. The latest studies of GOBMs in biomedical applications are critically reviewed, and in vitro and preclinical studies are assessed. Furthermore, the challenges likely to be faced and prospective future potential are addressed. GOBMs, a high potential emerging material, will dominate the materials of choice in the repair and development of human organs and medical devices. There is already great interest among academics as well as in pharmaceutical and biomedical industries.

Advances on Graphene-Based Nanomaterials and Mesenchymal Stem Cell-Derived Exosomes Applied in Cutaneous Wound Healing

Graphene is a new type of carbon nanomaterial discovered after fullerene and carbon nanotube. Due to the excellent biological properties such as biocompatibility, cell proliferation stimulating, and antibacterial properties, graphene and its derivatives have become emerging candidates for the development of novel cutaneous wound dressings and composite scaffolds. On the other hand, pre-clinical research on exosomes derived from mesenchymal stem cells (MSC-Exos) has been intensified for cell-free treatment in wound healing and cutaneous regeneration, via ameliorating the damaged microenvironment of the wound site. Here, we provide a comprehensive understanding of the latest studies and observations on the various effects of graphene-based nanomaterials (GBNs) and MSC-Exos during the cutaneous wound repair process, as well as the putative mechanisms thereof. In addition, we propose the possible forward directions of GBNs and MSC-Exos applications, expecting to promote the clinical transformation.

Alginate enriched with phytic acid for hydrogels preparation

Alginate hydrogels are extremely versatile and flexible biomaterials, with an enormous potential for bio-applications use. Their similarity with extracellular matrix is a key factor in their performance for cell and tissue regeneration. In this study superabsorbent high porous hydrogels based on sodium alginate physical crosslinked with a natural crosslinker compound namely phytic acid were prepared and evaluated from the viewpoint of their specific properties. The resulting hydrogels obtained with different ratios between alginate and phytic acid were characterized by Fourier transform infrared spectroscopy technique, scanning electron microscopy, XRD measurements, swelling tests in physiological environment, and thermal analysis by using a simultaneous TG/FT-IR/MS system. There are put into evidence the differences in physico-chemical properties of the hydrogels in relation with their composition, which endows them tunable properties and versatility.

Magneto-sensitive decellularized bone matrix with or without low frequency-pulsed electromagnetic field exposure for the healing of a critical-size bone defect

Bioactive ECM-based materials mimic the complex composition and structure of natural tissues. Decellularized cancellous bone matrix (DBM) has potential for guiding new bone formation and accelerating the regeneration process. On the other hand, low frequency-pulsed electromagnetic field (LF-PEMF) has been shown to enhance the regeneration capacity of bone defects. The present study sought to explore the feasibility of using DBM and DBM/MNP, and LF-PEMF for treating critical-size bone defects. Firstly, decellularization protocol was optimized to obtain a bioactive DBM, then MNPs were incorporated. Later, the physical, chemical and biological properties of DBM and DBM/MNP were assessed in vitro. MNPs homogeneously distributed into the DBM were not found to be toxic to human osteoblast cultures. Finally, an in vivo study was carried out with DBM and DBM/MNP composites in a bilateral critical-size rat cranial defect model (n = 48) with or without LF-PEMF exposure for 45 and 90 days. The histomorphometric and radiographic evaluations revealed that, while the collagen (positive control) and Sham (negative control) groups showed high incidence of fibrous connective tissue together with low level of osteogenic activity, both the DBM and DBM/MNP-grafted groups significantly promoted new bone tissue formation and angiogenesis, by the appropriate use of LF-PEMF for 90 days.

Nanocomposite scaffolds for accelerating chronic wound healing by enhancing angiogenesis

Skin is the body's first barrier against external pathogens that maintains the homeostasis of the body. Any serious damage to the skin could have an impact on human health and quality of life. Tissue engineering aims to improve the quality of damaged tissue regeneration. One of the most effective treatments for skin tissue regeneration is to improve angiogenesis during the healing period. Over the last decade, there has been an impressive growth of new potential applications for nanobiomaterials in tissue engineering. Various approaches have been developed to improve the rate and quality of the healing process using angiogenic nanomaterials. In this review, we focused on molecular mechanisms and key factors in angiogenesis, the role of nanobiomaterials in angiogenesis, and scaffold-based tissue engineering approaches for accelerated wound healing based on improved angiogenesis.

Plant based cross-linkers for tissue engineering applications

Utility of plant-based materials in tissue engineering has exponentially increased over the years. Recent efforts in this area have been focused on substituting synthetic cross-linkers with natural ones derived from biological sources. These cross-linkers are essentially derived from the vegetative components of plants therefore suitably categorised as 'green' and renewable materials. Utilization of plant based cross-linkers in scaffolds and hydrogels offers several advantages compared to the synthetic ones. Natural compounds, like ferulic acid and genipin, when incorporated into scaffolds can promote cellular proliferation and growth, by regulation of growth factors. They participate in crucial activities, thus providing impetus for cell growth, function, differentiation and angiogenesis. Several natural compounds inherently possess anti-microbial, antioxidant and anti-inflammatory effects, which enhance the inherent characteristics of the scaffolds. Versatility of natural cross-linkers can be exploited for diverse applications. Integrating such potent molecules can enable the scaffold to display relevant characteristics for each function. This review article focuses on the recent developments with plant based cross-linkers that are employed for scaffold synthesis and their applications, which may be explored to synthesize scaffolds suitable for diverse biomedical applications.

New Insight into Natural Extracellular Matrix: Genipin Cross-Linked Adipose-Derived Stem Cell Extracellular Matrix Gel for Tissue Engineering

The cell-derived extracellular matrix (ECM) is associated with a lower risk of pathogen transfer, and it possesses an ideal niche with growth factors and complex fibrillar proteins for cell attachment and growth. However, the cell-derived ECM is found to have poor biomechanical properties, and processing of cell-derived ECM into gels is scarcely studied. The gel provides platforms for three-dimensional cell culture, as well as injectable biomaterials, which could be delivered via a minimally invasive procedure. Thus, in this study, an adipose-derived stem cell (ADSC)-derived ECM gel was developed and cross-linked by genipin to address the aforementioned issue. The genipin cross-linked ADSC ECM gel was fabricated via several steps, including rabbit ADSC culture, cell sheets, decellularization, freeze-thawing, enzymatic digestion, neutralization of pH, and cross-linking. The physicochemical characteristics and cytocompatibility of the gel were evaluated. The results demonstrated that the genipin cross-linking could significantly enhance the mechanical properties of the ADSC ECM gel. Furthermore, the ADSC ECM was found to contain collagen, fibronectin, biglycan, and transforming growth factor (TGF)-β1, which could substantially maintain ADSC, skin, and ligament fibroblast cell proliferation. This cell-derived natural material could be suitable for future regenerative medicine and tissue engineering application.

Attachment of streptavidin-modified superparamagnetic iron oxide nanoparticles to the PC-12 cell membrane

Efficient attachment of magnetic nanoparticles to cell membranes plays an important role in the activation of cell membrane channels. Streptavidin (SA) was successfully modified to Poly (ethylene imine) (PEI)-superparamagnetic iron oxide nanoparticles (SPIONs) to form SA/PEI-SPIONs, which have high colloidal stability and low cytotoxicity. The SA/PEI-SPIONs were incubated with PC-12 cells which had first been cultured in a Roswell Park Memorial Institute medium 1640 containing 0.2 mg l^-1 biotin for 12 h. The cells were observed by transmission electron microscopy, and the nanoparticles were clearly attached on the cell membrane, which can be attributed to the specific binding between the SA and biotin sites on the cell surface. This work provides a simple way to attach SA-modified nanoparticles on the membranes of cells by only culturing cells in a biotin-containing medium. This work makes possible biomedical applications that require nanoparticles to target cell membranes.

Graphene Oxide-Based Nanomaterials: An Insight into Retinal Prosthesis

Retinal prosthesis has recently emerged as a treatment strategy for retinopathies, providing excellent assistance in the treatment of age-related macular degeneration (AMD) and retinitis pigmentosa. The potential application of graphene oxide (GO), a highly biocompatible nanomaterial with superior physicochemical properties, in the fabrication of electrodes for retinal prosthesis, is reviewed in this article. This review integrates insights from biological medicine and nanotechnology, with electronic and electrical engineering technological breakthroughs, and aims to highlight innovative objectives in developing biomedical applications of retinal prosthesis.

Regeneration of skeletal system with genipin crosslinked biomaterials

Natural biomaterials, such as collagen, gelatin, and chitosan, are considered as promising candidates for use in tissue regeneration treatment, given their similarity to natural tissues regarding components and structure. Nevertheless, only receiving a crosslinking process can these biomaterials exhibit sufficient strength to bear high tensile loads for use in skeletal system regeneration. Recently, genipin, a natural chemical compound extracted from gardenia fruits, has shown great potential as a reliable crosslinking reagent, which can reconcile the crosslinking effect and biosafety profile simultaneously. In this review, we briefly summarize the genipin extraction process, biosafety, and crosslinking mechanism. Subsequently, the applications of genipin regarding aiding skeletal system regeneration are discussed in detail, including the advances and technological strategies for reconstructing cartilage, bone, intervertebral disc, tendon, and skeletal muscle tissues. Finally, based on the specific pharmacological functions of genipin, its potential applications, such as its use in bioprinting and serving as an antioxidant and anti-tumor agent, and the challenges of genipin in the clinical applications in skeletal system regeneration are also presented.

The effect of human platelet lysate on the differentiation ability of human adipose-derived stem cells cultured on ECM-coated surfaces

Human mesenchymal stem cells (hMSCs), such as human adipose-derived stem cells (hADSCs), present heterogeneous characteristics, including varying differentiation abilities and genotypes. hADSCs isolated under different conditions exhibit differences in stemness. We isolated hADSCs from human fat tissues via culture on different cell culture biomaterials including tissue culture polystyrene (TCPS) dishes and extracellular matrix protein (ECM)-coated dishes in medium supplemented with 5% or 10% serum-converted human platelet lysate (hPL) or 10% fetal bovine serum (FBS) as a control. Currently, it is not clear whether xeno-free hPL in the cell culture medium promotes the ability of hMSCs such as hADSCs to differentiate into several cell lineages compared to the xenomaterial FBS. We investigated whether a synchronized effect of ECM (Matrigel, fibronectin, and recombinant vitronectin) coatings on TCPS dishes for efficient hADSC differentiation could be observed when hADSCs were cultured in hPL medium. We found that Matrigel-coated dishes promoted hADSC differentiation into osteoblasts and suppressed differentiation into chondrocytes in 10% hPL medium. Recombinant vitronectin- and fibronectin-coated dishes greatly promoted hADSC differentiation into osteoblasts and chondrocytes in 5% and 10% hPL media. hPL promoted hADSC differentiation into osteoblasts and chondrocytes compared to FBS on the fibronectin-coated surface and recombinant vitronectin-coated surface.

Do biomedical engineers dream of graphene sheets?

During the past few years, graphene has outstandingly emerged as a key nanomaterial for boosting the performance of commercial, industrial and scientific related technologies. The popularity of this novel nanomaterial in biomedical engineering is due to its excellent biological, electronic, optical and thermal properties that, as a whole, surpass the features of commonly used biomaterials and consequently open a wide range of applications so far within the reach of science fiction. In this minireview, the potential of graphene and its based materials in the expanding biomedical field is highlighted with focus on groundbreaking diagnostic, monitoring and therapeutic strategies. Some of the major challenges related to the synthesis and safety of graphene-based materials are also briefly discussed because of their critical importance in bringing this class of carbon materials closer to the clinic.

PLGA–collagen–ECM hybrid scaffolds functionalized with biomimetic extracellular matrices secreted by mesenchymal stem cells during stepwise osteogenesis-co-adipogenesis

Development of an in vitro 3D model that reflects the dynamic remodeling of ECMs during simultaneous osteogenesis and adipogenesis of hMSCs.

Bionic cartilage acellular matrix microspheres as a scaffold for engineering cartilage

Bionic cartilage acellular matrix microspheres (BCAMMs) made from decelluarized bionic cartilage microspheres (BCMs).

Biomimetic Porifera Skeletal Structure of Lead-Free Piezocomposite Energy Harvesters

The elastic composite-based piezoelectric energy-harvesting technology is highly desired to enable a wide range of device applications, including self-powered wearable electronics, robotic skins, and biomedical devices. Recently developed piezoelectric composites are based on inorganic piezoelectric fillers and polymeric soft matrix to take advantages of both components. However, there are still limitations such as weak stress transfer to piezoelectric elements and poor dispersion of fillers in matrix. In this report, a highly enhanced piezocomposite energy harvester (PCEH) is developed using a three-dimensional electroceramic skeleton by mimicking and reproducing the sea porifera architecture. This new mechanically reinforced PCEH is demonstrated to resolve the problems of previous reported conventional piezocomposites and in turn induces stronger piezoelectric energy-harvesting responses. The generated voltage, current density, and instantaneous power density of the biomimetic PCEH device reach up to ∼16 times higher power output than that of conventional randomly dispersed particle-based PCEH. This work broadens further developments of the high-output elastic piezocomposite energy harvesting and sensor application with biomimetic architecture.