The skin is the body's first line of defence, and its physiology is complex. When injury occurs, the skin goes through a complex recovery process, and there is the risk of developing a chronic wound. Therefore, proper wound care is critical during the healing process. In response to clinical needs, wound dressings have been developed. There are several types of wound dressings available for wound healing, but there are still many issues to overcome. With its high controllability and resolution, three-dimensional (3D) printing technology is widely regarded as the technology of the next global industrial and manufacturing revolution, and it is a key driving force in the development of wound dressings. Here, we briefly introduce the wound healing mechanism, organize the history and the main technologies of 3D bioprinting, and discuss the application as well as the future direction of development of 3D bioprinting technology in the field of wound dressings.

The development of hydrogel based scaffold with the capability of enhanced antibacterial effects and wound healing is the promising strategy for the treatment of wound tissues with bacterial infection. Herein, we fabricated a hollow channeled hydrogel scaffold based on the mixture of dopamine modified alginate (Alg-DA) and gelatin via co-axial 3D printing for the treatment of bacterial-infected wound. The scaffold was crosslinked by copper/calcium ions, which could enhance the structural stability and mechanical properties. Meanwhile, copper ions crosslinking endowed the scaffold with good photothermal effects. The photothermal effect and copper ions showed excellent antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Moreover, the hollow channels and the sustained released copper ions could stimulate angiogenesis and accelerate wound healing process. Thus, the prepared hollow channeled hydrogel scaffold might be a potential candidate for promoting wound healing application.

Biocompatibility is one of the key issues for implants, especially in the case of stainless steel with medium to low biocompatibility, which may lead to a lack of osseointegration and consequently to implant failure or rejection. To precisely control preferential cell growth sites and, consequently, the biocompatibility of prosthetic devices, two types of surfaces were analyzed, containing periodic nanogrooves laser induced periodic surface structure (LIPSS) and square-shaped micropillars. For the fast and efficient production of these surfaces, the unique combination of high energy ultrashort pulsed laser system with multi-beam and beamshaping technology was applied, resulting in increased productivity by 526% for micropillars and 14 570% for LIPSS compared to single beam methods. In vitro analysis revealed that micro and nanostructured surfaces provide a better environment for cell attachment and proliferation compared to untreated ones, showing an increase of up to 496% in the number of cells compared to the reference. Moreover, the combination of LIPSS and micropillars resulted in a precise cell orientation along the periodic microgroove pattern. The combination of these results demonstrates the possibility of mass production of functionalized implants with control over cell organization and growth. Thus, reducing the risk of implant failure due to low biocompatibility.

Niacin (NA) and zinc (Zn) were used to fabricate metal organic frameworks (Zn-NA MOFs), based on coordination chemistry via a simple, rapid technique conducted at room temperature. The identity of the prepared MOFs was confirmed by Fourier-transform infrared, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy, which showed cubic shaped, crystalline, microporous MOFs with an average size of 150 nm. Release of the active ingredients from the MOFs was proved to be pH dependent in a slightly alkaline medium (pH 8.5) with a sustained release rate of its two ingredients, NA and Zn, which have wound healing activity. Zn-NA MOFs proved to be biocompatible in the tested concentrations range (5-100 mg ml-1), with no cytotoxic effect on WI-38 cell line. Zn-NA MOFs at 10 and 50 mg ml-1concentrations and their components, NA and Zn, exerted antibacterial effects againstStaphylococcus aureus, Escherichia coli, andPseudomonas aeruginosa. Wound healing effect of the Zn-NA MOFs (50 mg ml-1) was evaluated on full excisional rat wounds. Significant reduction of the wound area was observed after 9 d of treatment using the Zn-NA MOFs compared to the other treatment groups. Additionally, wounds were fully healed after 10 d of treatment with the Zn-NA MOFs with histological and immunohistochemical evidence of re-epithelization, collagen formation, and angiogenesis. Similar histological evidence was also observed in wounds treated with niacin only; however, with no significant wound closure rates. Nevertheless, the formation of new blood vessels, as confirmed by the vascular endothelial growth factor protein expression, was highest in the niacin group. Zn-NA MOFs synthesized using a facile, low-cost method are potentially capable of healing wounds rapidly and effectively.

Artificial nerve grafts that support axon growth hold promises in promoting nerve regeneration and function recovery. However, current artificial nerve grafts are insufficient to regenerate axons across long nerve gaps. Specific biochemical and biophysical cues are required to be incorporated to artificial nerve grafts to promote neural cell adhesion and guide neurite outgrowth. Polyvinyl alcohol (PVA) nerve conduit has been clinically approved, but the applicability of PVA nerve conduits is limited to short injuries due to low cell binding. In this study, we explored the incorporation of biochemical cues and topographical cues for promoting neuritogenesis and axon guidance. PVA was conjugated with extracellular matrix proteins and fucoidan, a bioactive sulfate polysaccharide, to improve cell adhesion. Micro-sized topographies, including 1.8 μm convex lenses, 2 μm gratings, and 10 μm gratings were successfully fabricated on PVA by nanofabrication, and the synergistic effects of topography and biochemical molecules on pheochromocytoma 12 (PC12) neuritogenesis and neurite alignment were studied. Conjugated fucoidan promoted the percentage of PC12 with neurite outgrowth from 0 to 2.8% and further increased to 5% by presenting laminin on the surface. Additionally, fucoidan was able to bind nerve growth factor (NGF) on the surface and allow for PC12 to extend neurites in NGF-free media. The incorporation of 2 μm gratings could double the percentage of PC12 with neurite outgrowth and neurite length, and guided the neurites to extend along the grating axis. The work presents a promising strategy to enhance neurite formation and axon guidance, presenting significant value in promoting nerve regeneration.

Bio-based hydrogels as three-dimensional (3D) constructs have attracted attention in advanced tissue engineering. Compared with conventional two-dimensional (2D) cell culture, cells grown in 3D scaffolds are expected to demonstrate the inherent behavior of living organisms of cellular spheroids. Herein, we constructed cell-laden nanofiber-based hydrogels in combination with 2,2,6,6-tetramethylpiperidine 1-oxyl-oxidized cellulose nanofiber (TOCNF) and chitosan nanofiber (CsNF) for bioadaptive liver tissue engineering. The carboxylates of TOCNF and amines of CsNF were directly crosslinked via EDC/NHS chemistry. The rheological properties of the solutions for the nanofibers and hydrogels revealed sufficient physical properties for the injection, printing, and plotting process, as well as significant encapsulation of living cells. As-designed hydrogels exhibited excellent viscoelastic properties with typical shear-thinning behavior, and had a storage modulus of 1234 Pa ± 68 Pa, suitable for cell culture. Non-cytotoxicity was confirmed using a live/dead assay with mouse-derived fibroblast NIH/3T3 cells. Human hepatocellular carcinoma HepG2 cells could be cultured on a gel surface (2D environment) and encapsulated in the gel structure (3D environment), which enabled 10 d growth with high gene expression level of albumin of HepG2 spheroids in the 3D gels. The biodegradable cell-laden hydrogels are expected to mimic the cellular microenvironment and provide potential for bioadaptive 3D cell cultures in biomedical applications.

Multi-model combination treatment of malignant tumors can make up for the shortcomings of single treatment through multi-target and multi-path to achieve more ideal tumor treatment effect. However, the mutual interference of different drugs in the delivery processin vivoand the difficulty of effective drug accumulation in tumor cells are the bottlenecks of combined therapy. To this project, light-responsive liposomes loading doxorubicin (DOX) and chlorin e6 (Ce6) (DOX-Ce6-Lip) without mutual interference were engineered by thin film hydration method. This kind of nano-drug delivery system increased the drugs concentration accumulated in tumor sites through enhanced permeability and retention effect, and reduced the toxic and side effects of drugs on normal tissuesin vivo. In addition, after entering the tumor cells, Ce6 produced a large number of reactive oxygen species under 660 nm NIR laser irradiation, which further oxidized the unsaturated fatty acid chain in the liposomes and caused the collapse of the liposomes, thus realizing the stimulus-responsive release of Ce6 and DOX. The concentrations of DOX and Ce6 in the tumor cells rapidly reached the peak and achieved a more effective combination of chemotherapy and photodynamic therapy (PDT). Consequently, DOX-Ce6-Lip followed by 660 nm NIR irradiation achieved an efficient tumor growth inhibition of 71.90 ± 3.14%, indicating the versatile potential of chemotherapy and PDT. In conclusion, this study provides a delivery scheme for drugs with different solubilities and an effectively combined anti-tumor therapy method.

In this study, chitosan-gelatin-monetite (CGM)-based electrospun scaffolds have been developed that closely mimicked the microstructure and chemical composition of the extracellular matrix of natural bone. CGM-based nanofibrous composite scaffolds were prepared with the help of the electrospinning technique, post-cross-linked using EDC and NHS solution to improve their stability in an aqueous environment. The prepared CG scaffold showed an average fiber diameter of 284 ± 17 nm, whereas 5 and 7 wt% monetite containing CGM5 and CGM7 scaffolds, exhibited an average fiber diameter of 390 ± 11 and 435 ± 15 nm, respectively, revealing the fine distribution of monetite particles on the fibrous surface. The distribution of monetite nanoparticles onto the CG nanofibrous surface was confirmed using XRD, FTIR, and EDAX. Moreover, the addition of 7 wt% monetite into the CG electrospun matrix increased their ultimate tensile strength from 2.01 ± 0.05 MPa in the CG scaffold to 11.68 ± 0.09 MPa in the CGM7 scaffold. SBF study and staining with ARS confirmed the higher mineralization ability of monetite-containing scaffolds compared to that revealed by the CG scaffold. The monetite incorporation into the CG matrix improved its osteogenic properties, including pre-osteoblast MG-63 cell adhesion, proliferation, and differentiation, when seeded with the cells. A higher degree of cellular adhesion, spreading, and migration was observed on the monetite-incorporated CG scaffold than that on the CG scaffold. From MTT assay, ALP activity, ARS staining, and immunocytochemistry study, the cultured cells discovered a more conducive microenvironment to proliferate and subsequently differentiate into osteoblast lineage in contact with CGM7 nanofibers rather than that in CGM0 and CGM5. In-vitro results indicated that electrospun CGM-based composite scaffolds could be used as a potential candidate to repair and regenerate new bone tissues. .

Hydrogels have drawn much attention in the field of tissue regeneration and wound healing owing to the application of biocompatible peptides to tailor structural features necessitating optimal tissue remodeling performance. In the current study, polymers and peptide were explored to develop scaffolds for wound healing and skin tissue regeneration. Alginate (Alg), chitosan (CS), and arginine-glycine-aspartate (RGD) were used to fabricate composite scaffolds crosslinked with tannic acid (TA), which also served as a bioactive. The use of RGD transformed the physicochemical and morphological features of the 3D scaffolds and TA crosslinking of the scaffolds improved their mechanical properties, specifically tensile strength, compressive Young’s modulus, yield strength, and ultimate compressive strength. The incorporation of TA as both a crosslinker and a bioactive allowed for 86% encapsulation efficiency and burst release of 57% of TA in 24 h, accompanied by an 8.5% steady release per day of up to 90% over 5 d. The scaffolds increased mouse embryonic fibroblast cell viability over 3 d, progressing from slightly cytotoxic to non-cytotoxic (cell viability >90%). Wound closure and tissue regeneration evaluations in a SpragueDawley rat wound model at predetermined wound healing time points highlighted the superiority of the Alg-RGD-CS and Alg-RGD-CS-TA scaffolds over the commercial comparator product and control. The scaffolds’ superior performance included accelerated tissue remodeling performance from the early to the late stages of wound healing, indicated by the lack of defects and scarring in scaffold-treated tissues. This promising performance supports the design of wound dressings that can act as delivery systems for the treatment of acute and chronic wounds.

Podophyllotoxin (PPT) is an active natural pharmaceutical component with potent anticancer activity. However, due to its poor water solubility and serious side effects, its medical applications are limited. In this work, we synthesized a series of PPT dimers, which can be self-assembled into stable nanoparticles of 124–152 nm in aqueous solution and can significantly increase the solubility of PPT in aqueous solution. In addition, PPT dimer nanoparticles exhibited high drug loading capacity (>80%) and could store at 4 °C in aqueous state with good stability for at least 30 d. In vitro release studies showed that nanoparticles with disulfide bonds (SS NPs) can quickly release (about 96.5% drug released within 24 h) the conjugated drug in PBS buffer (pH = 7.4) in the presence of DTT. Cell endocytosis experiments showed that SS NPs enhanced cell uptake (18.56 times higher than PPT for Molm-13, 10.29 times for A2780S and 9.81 times for A2780T) and maintained antitumor effect against human ovarian tumor cells (A2780S and resistant A2780T) and human breast cancer cells (MCF-7). In addition, the endocytosis mechanism of SS NPs was revealed that these nanoparticles were mainly up-taken by macropinocytosis-mediated endocytosis. We believe that these PPT dimer-based nanoparticles will become an alternative formula for PPT, moreover the assembly behavior of PPT dimer can be extended to other therapeutic drugs.

Although extensive studies have evaluated the regulation effect of microenvironment on cell phenotype and cell differentiation, further investigations in the field of the cornea are needed to gain sufficient knowledge for possible clinical translation. This study aims to evaluate the regulation effects of substrate stiffness and inflammation on keratocyte phenotype of corneal fibroblasts, as well as the differentiation from stem cells towards keratocytes. Soft and stiff substrates were prepared based on polydimethylsiloxane. HTK and stem cells were cultured on these substrates to evaluate the effects of stiffness. The possible synergistic effects between substrate stiffness and inflammatory factor IL-1β were examined by qPCR and immunofluorescence staining. In addition, macrophages were cultured on soft and stiff substrates to evaluate the effect of substrate stiffness on the synthesis of inflammatory factors. The conditioned medium of macrophages (Soft-CM and Stiff-CM) was collected to examine the effects on HTK and stem cells. It was found that inflammatory factor IL-1β promoted keratocyte phenotype and differentiation when cells were cultured on soft substrate (∼130 kPa), which were different from cells cultured on stiff substrate (∼2 × 103 kPa) and TCP (∼106 kPa). Besides, macrophages cultured on stiff substrates had significantly higher expression of IL-1β and Tnf-α as compared to the cells cultured on soft substrates. And Stiff-CM decreased the expression of keratocyte phenotype markers as compared to Soft-CM. The results of our study indicate a stiffness-dependent dynamic effect of inflammation on keratocyte phenotype and differentiation, which is of significance not only in gaining a deeper knowledge of corneal pathology and repair, but also in being instructive for scaffold design in corneal tissue engineering and ultimate regeneration.

Cancer severely threatens human health, which makes it particularly urgent to develop effective strategies for cancer diagnosis and therapy. Gene therapy and nucleic acid-based cancer diagnosis play important roles in cancer theranostic, but their applicability is challenged by the low cellular uptake and enzymatic degradation. In response, safe and efficient carrier metal-organic frameworks (MOFs) have been proposed. Zeolite imidazole frameworks (ZIFs), a promising MOF type, can easily encapsulate negatively charged nucleic acid while offering a high loading efficiency, adjustable structure, and conditional responsiveness (pH, adenosine triphosphate (ATP), or glutathione (GSH)). In this review, we studied recent articles on nucleic acid-loading ZIFs-based nanoplatforms in tumor theranostics on the Pubmed database, with a focus on the synthesis and applications in tumor diagnosis and treatment. The relevant favorable aspects, potential challenges, and future opportunities are also discussed in this review.

Carbon dots (CDs) are novel zero-dimensional spherical nanoparticles with water solubility, biocompatibility and photoluminescence properties. As the variety of raw materials for CDs synthesis becomes more and more abundant, people tend to choose precursors from nature. Many recent studies have shown that CDs can inherit properties similar to their carbon sources. Chinese herbal medicine has a variety of therapeutic effects to many diseases. In recent years, many literatures have chosen herbal medicine as raw materials, however, how the properties of raw materials affect CDs has not been systematically summarized. The intrinsic bioactivity and potential pharmacological effects of CDs have not received sufficient attention and have become a 'blind spot' for research. In this paper, the main synthesis methods were introduced and the effects of carbon sources from different herbal medicine on the properties of CDs and related applications were reviewed. In addition, we briefly review some of the biosafety assessments of CDs, and make recommendations for biomedical applications. CDs that inherit the therapeutic properties of herbs can enable diagnosis and treatment of clinical diseases, bioimaging, and biosensing in the future.

Wound or injury is a breakdown in the skin’s protective function as well as damage to the normal tissues. Wound healing is a dynamic and complex phenomenon of replacing injured skin or body tissues. In ancient times the Calendula officinalis and Hibiscus rosa-sinensis flowers were extensively used by the tribal communities as herbal medicine for various complications including wound healing. But loading and delivery of such herbal medicines are challenging because it maintains their molecular structure against temperature, moisture, and other ambient factors. This study has fabricated xanthan gum (XG) hydrogel through a facile process and encapsulated C. officinalis and H. rosa-sinensis flower extract. The resulting hydrogel was characterized by different physical methods like x-ray diffractometer, UV–vis spectroscopy, Fourier transform infrared spectroscopy, SEM, dynamic light scattering, electronkinetic potential in colloidal systems (ZETA) potential, thermogravimetric differential thermal analysis (TGA-DTA), etc. The polyherbal extract was phytochemically screened and observed that flavonoids, alkaloids, terpenoids, tannins, saponins, anthraquinones, glycosides, amino acids, and a few percentages of reducing sugar were present in the polyherbal extract. Polyherbal extract encapsulated XG hydrogel (X@C–H) significantly enhanced the proliferation of fibroblast and keratinocyte cell lines in comparison to the bare excipient treated cells as determined by 3-(4, 5-dimethylthiazol-2-Yl)-2, 5-diphenyltetrazolium bromide assay. Also, the proliferation of these cells was confirmed by BrdU assay and enhanced expression of pAkt. In an in-vivo study, wound healing activity of BALB/c mice was carried out and we observed that X@C–H hydrogel showed significant result compared to the other groups (untreated, X, X@C, X@H). Henceforth, we conclude that this synthesized biocompatible hydrogel could emerge as a promising carrier of more than one herbal excipients.

With the advent of nanotechnology, there has been an extensive interest in the antimicrobial potential of metals. The rapid and widespread development of antimicrobial-resistant and multidrug-resistant bacteria has prompted recent research into developing novel or alternative antimicrobial agents. In this study, the antimicrobial efficacy of metallic copper, cobalt, silver and zinc nanoparticles was assessed against Escherichia coli (NCTC 10538), S. aureus (ATCC 6538) along with three clinical isolates of Staphylococcus epidermidis (A37, A57 and A91) and three clinical isolates of E. coli (Strains 1, 2 and 3) recovered from bone marrow transplant patients and patients with cystitis respectively. Antimicrobial sensitivity assays, including agar diffusion and broth macro-dilution to determine minimum inhibitory and bactericidal concentrations (MIC/MBC) and time-kill/synergy assays, were used to assess the antimicrobial efficacy of the agents. The panel of test microorganisms, including antibiotic-resistant strains, demonstrated a broad range of sensitivity to the metals investigated. MICs of the type culture strains were in the range of 0.625–5.0 mg ml−1. While copper and cobalt exhibited no difference in sensitivity between Gram-positive and Gram-negative microorganisms, silver and zinc showed strain specificity. A significant decrease (p < 0.001) in the bacterial density of E. coli and S. aureus was demonstrated by silver, copper and zinc in as little as two hours. Furthermore, combining metal nanoparticles reduced the time required to achieve a complete kill.

TiO2 nanotubes (TNTs) significantly promote osteogenic differentiation and bone regeneration of cells. Nevertheless, the biological processes by which they promote osteogenesis are currently poorly understood. Long non-coding RNAs (lncRNAs) are essential for controlling osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Epigenetic chromatin modification is one of the pathways in which lncRNAs regulate osteogenic differentiation. Here, we reported that TNTs could upregulate lncRNA RMRP, and inhibition of lncRNA RMRP in human bone marrow mesenchymal stem cells (hBMSCs) grown on TNTs could decrease runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), osteopontin (OPN), and osteocalcin (OCN) expression. Furthermore, we discovered that inhibiting lncRNA RMRP elevated the expression of lncRNA DLEU2, and lncRNA DLEU2 knockdown promoted osteogenic differentiation in hBMSCs. RNA immunoprecipitation (RIP) experiments showed that lncRNA DLEU2 could interact with EZH2 to induce H3K27 methylation in the promoter regions of RUNX2 and OCN, suppressing gene expression epigenetically. According to these results, lncRNA RMRP is upregulated by TNTs to promote osteogenic differentiation through DLEU2/EZH2-mediated epigenetic modifications.

Although there have been many advances in injectable hydrogels as scaffolds for tissue engineering or as payload-containing vehicles, the lack of adequate microporosity for the desired cell behavior, tissue integration, and successful tissue generation remains an important drawback. Herein, we describe an effective porous injectable system that allows in vivo formation of pores through conventional syringe injection at room temperature. This system is based on the differential melting profiles of photocrosslinkable salmon gelatin and physically crosslinked porogens of porcine gelatin (PG), in which PG porogens are solid beads, while salmon methacrylamide gelatin remains liquid during the injection procedure. After injection and photocrosslinking, the porogens were degraded in response to the physiological temperature, enabling the generation of a homogeneous porous structure within the hydrogel. The resultant porogen-containing formulations exhibited controlled gelation kinetics within a broad temperature window (18.5 ± 0.5–28.8 ± 0.8 °C), low viscosity (133 ± 1.4–188 ± 16 cP), low force requirements for injectability (17 ± 0.3–39 ± 1 N), robust mechanical properties after photo-crosslinking (100.9 ± 3.4–332 ± 13.2 kPa), and favorable cytocompatibility (>70% cell viability). Remarkably, in vivo subcutaneous injection demonstrated the suitability of the system with appropriate viscosity and swift crosslinking to generate porous hydrogels. The resulting injected porous constructs showed favorable biocompatibility and facilitated cell infiltration for desirable potential tissue remodeling. Finally, the porogen-containing formulations exhibited favorable handling, easy deposition, and good shape fidelity when used as bioinks in 3D bioprinting technology. This injectable porous system serves as a platform for various biomedical applications, thereby inspiring future advances in cell therapy and tissue engineering.