Glycinamide Facilitates Nanocomplex Formation and Functions Synergistically with Bone Morphogenetic Protein 2 to Promote Osteoblast Differentiation In Vitro and Bone Regeneration in a Mouse Calvarial Defect Model.

BACKGROUND: This study aimed to identify glycine analogs conducive to the formation of cell-absorbable nanocomplexes, enhancing collagen synthesis and subsequent osteogenesis in combination with BMP2 for improved bone regeneration. METHODS: Glycine and its derivatives were assessed for their effects on osteogenic differentiation in MC3T3-E1 cells and human bone marrow mesenchymal stem cells (BMSCs) under osteogenic conditions or with BMP2. Osteogenic differentiation was assessed through alkaline phosphatase staining and real-time quantitative polymerase chain reaction (RT-qPCR). Nanocomplex formation was examined via scanning electron microscopy, circular dichroism, and ultraviolet-visible spectroscopy. In vivo osteogenic effects were validated using a mouse calvarial defect model, and bone regeneration was evaluated through micro-computed tomography and histomorphometric analysis. RESULTS: Glycine, glycine methyl ester, and glycinamide significantly enhanced collagen synthesis and ALP activity in conjunction with an osteogenic medium (OSM). GA emerged as the most effective inducer of osteoblast differentiation marker genes. Combining GA with BMP2 synergistically stimulated ALP activity and the expression of osteoblast markers in both cell lines. GA readily formed nanocomplexes, facilitating cellular uptake through strong electrostatic interactions. In an in vivo calvarial defect mouse model, the GA and BMP2 combination demonstrated enhanced bone volume, bone volume/tissue volume ratio, trabecular numbers, and mature bone formation compared to other combinations. CONCLUSION: GA and BMP2 synergistically promoted in vitro osteoblast differentiation and in vivo bone regeneration through nanocomplex formation. This combination holds therapeutic promise for individuals with bone defects, showcasing its potential for clinical intervention.

Self-assembling biomolecules for biosensor applications.

Molecular self-assembly has received considerable attention in biomedical fields as a simple and effective method for developing biomolecular nanostructures. Self-assembled nanostructures can exhibit high binding affinity and selectivity by displaying multiple ligands/receptors on their surface. In addition, the use of supramolecular structure change upon binding is an intriguing approach to generate binding signal. Therefore, many self-assembled nanostructure-based biosensors have been developed over the past decades, using various biomolecules (e.g., peptides, DNA, RNA, lipids) and their combinations with non-biological substances. In this review, we provide an overview of recent developments in the design and fabrication of self-assembling biomolecules for biosensing. Furthermore, we discuss representative electrochemical biosensing platforms which convert the biochemical reactions of those biomolecules into electrical signals (e.g., voltage, ampere, potential difference, impedance) to contribute to detect targets. This paper also highlights the successful outcomes of self-assembling biomolecules in biosensor applications and discusses the challenges that this promising technology needs to overcome for more widespread use.

Radiation induces acute and subacute vascular regression in a three-dimensional microvasculature model.

Radiation treatment is one of the most frequently used therapies in patients with cancer, employed in approximately half of all patients. However, the use of radiation therapy is limited by acute or chronic adverse effects and the failure to consider the tumor microenvironment. Blood vessels substantially contribute to radiation responses in both normal and tumor tissues. The present study employed a three-dimensional (3D) microvasculature-on-a-chip that mimics physiological blood vessels to determine the effect of radiation on blood vessels. This model represents radiation-induced pathophysiological effects on blood vessels in terms of cellular damage and structural and functional changes. DNA double-strand breaks (DSBs), apoptosis, and cell viability indicate cellular damage. Radiation-induced damage leads to a reduction in vascular structures, such as vascular area, branch length, branch number, junction number, and branch diameter; this phenomenon occurs in the mature vascular network and during neovascularization. Additionally, vasculature regression was demonstrated by staining the basement membrane and microfilaments. Radiation exposure could increase the blockage and permeability of the vascular network, indicating that radiation alters the function of blood vessels. Radiation suppressed blood vessel recovery and induced a loss of angiogenic ability, resulting in a network of irradiated vessels that failed to recover, deteriorating gradually. These findings demonstrate that this model is valuable for assessing radiation-induced vascular dysfunction and acute and chronic effects and can potentially improve radiotherapy efficiency.

The Effect of the Mechanical Properties of the 3D Printed Gelatin/Hyaluronic Acid Scaffolds on hMSCs Differentiation Towards Chondrogenesis.

BACKGROUND: Tissue engineering, including 3D bioprinting, holds great promise as a therapeutic tool for repairing cartilage defects. Mesenchymal stem cells have the potential to treat various fields due to their ability to differentiate into different cell types. The biomimetic substrate, such as scaffolds and hydrogels, is a crucial factor that affects cell behavior, and the mechanical properties of the substrate have been shown to impact differentiation during incubation. In this study, we examine the effect of the mechanical properties of the 3D printed scaffolds, made using different concentrations of cross-linker, on hMSCs differentiation towards chondrogenesis. METHODS: The 3D scaffold was fabricated using 3D bioprinting technology with gelatin/hyaluronic acid (HyA) biomaterial ink. Crosslinking was achieved by using different concentrations of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methlymorpholinium chloride n-hydrate (DMTMM), allowing for control of the scaffold's mechanical properties. The printability and stability were also evaluated based on the concentration of DMTMM used. The effects of the gelatin/HyA scaffold on chondrogenic differentiation was analyzed by utilizing various concentrations of DMTMM. RESULTS: The addition of HyA was found to improve the printability and stability of 3D printed gelatin/HyA scaffolds. The mechanical properties of the 3D gelatin/HyA scaffold could be regulated through the use of different concentrations of DMTMM cross-linker. In particular, the use of 0.25 mM DMTMM for crosslinking the 3D gelatin/HyA scaffold resulted in enhanced chondrocyte differentiation. CONCLUSION: The mechanical properties of 3D printed gelatin/HyA scaffolds cross-linked using various concentrations of DMTMM can influence the differentiation of hMSCs into chondrocytes.

Nebivolol Sensitizes BT-474 Breast Cancer Cells to FGFR Inhibitors.

BACKGROUND/AIM: The fibroblast growth factor receptor (FGFR) signaling pathway is abnormally activated in human cancers, including breast cancer. Therefore, targeting the FGFR signaling pathway is a potent strategy to treat breast cancer. The purpose of this study was to find drugs that could increase sensitivity to FGFR inhibitor effects in BT-474 breast cancer cells, and to investigate the combined effects and underlying mechanisms of these combinations for BT-474 breast cancer cell survival. MATERIALS AND METHODS: Cell viability was measured by MTT assay. Protein expression was determined by western blot analysis. mRNA expression was detected by Real-time PCR. Drug synergy effect was determined by isobologram analysis. RESULTS: Nebivolol, a third generation ß1-blocker, synergistically increased the sensitivity of BT-474 breast cancer cells to the potent and selective FGFR inhibitors erdafitinib (JNJ-42756493) and AZD4547. A combination of nebivolol and erdafitinib markedly reduced AKT activation. Suppression of AKT activation using specific siRNA and a selective inhibitor further enhanced cell sensitivity to combined treatment with nebivolol and erdafitinib, whereas SC79, a potent activator of AKT, reduced cell sensitivity to nebivolol and erdafitinib. CONCLUSION: Enhanced sensitivity of BT-474 breast cancer cells to nebivolol and erdafitinib was probably associated with down-regulation of AKT activation. Combined treatment with nebivolol and erdafitinib is a promising strategy for breast cancer treatment.

Stem cell laden nano and micro collagen/PLGA bimodal fibrous patches for myocardial regeneration.

BACKGROUND: Although the use of cardiac patches is still controversial, cardiac patch has the significance in the field of the tissue engineered cardiac regeneration because it overcomes several shortcomings of intra-myocardial injection by providing a template for cells to form a cohesive sheet. So far, fibrous scaffolds fabricated using electrospinning technique have been increasingly explored for preparation of cardiac patches. One of the problems with the use of electrospinning is that nanofibrous structures hardly allow the infiltration of cells for development of 3D tissue construct. In this respect, we have prepared novel bi-modal electrospun scaffolds as a feasible strategy to address the challenges in cardiac tissue engineering . METHODS: Nano/micro bimodal composite fibrous patch composed of collagen and poly (D, L-lactic-co-glycolic acid) (Col/PLGA) was fabricated using an independent nozzle control multi-electrospinning apparatus, and its feasibility as the stem cell laden cardiac patch was systemically investigated. RESULTS: Nano/micro bimodal distributions of Col/PLGA patches without beaded fibers were obtained in the range of the 4-6% collagen concentration. The poor mechanical properties of collagen and the hydrophobic property of PLGA were improved by co-electrospinning. In vitro experiments using bone marrow-derived mesenchymal stem cells (BMSCs) revealed that Col/PLGA showed improved cyto-compatibility and proliferation capacity compared to PLGA, and their extent increased with increase in collagen content. The results of tracing nanoparticle-labeled as well as GFP transfected BMSCs strongly support that Col/PLGA possesses the long-term stem cells retention capability, thereby allowing stem cells to directly function as myocardial and vascular endothelial cells or to secrete the recovery factors, which in turn leads to improved heart function proved by histological and echocardiographic findings. CONCLUSION: Col/PLGA bimodal cardiac patch could significantly attenuate cardiac remodeling and fully recover the cardiac function, as a consequence of their potent long term stem cell engraftment capability.

NPFFR2 Contributes to the Malignancy of Hepatocellular Carcinoma Development by Activating RhoA/YAP Signaling.

G protein-coupled receptors (GPCRs) are a diverse family of cell surface receptors implicated in various physiological functions, making them common targets for approved drugs. Many GPCRs are abnormally activated in cancers and have emerged as therapeutic targets for cancer. Neuropeptide FF receptor 2 (NPFFR2) is a GPCR that helps regulate pain and modulates the opioid system; however, its function remains unknown in cancers. Here, we found that NPFFR2 is significantly up-regulated in liver cancer and its expression is related to poor prognosis. Silencing of NPFFR2 reduced the malignancy of liver cancer cells by decreasing cell survival, invasion, and migration, while its overexpression increased invasion, migration, and anchorage-independent cell growth. Moreover, we found that the malignant function of NPFFR2 depends on RhoA and YAP signaling. Inhibition of Rho kinase activity completely restored the phenotypes induced by NPFFR2, and RhoA/F-Actin/YAP signaling was controlled by NPFFR2. These findings demonstrate that NPFFR2 may be a potential target for the treatment of hepatocellular carcinoma.

Knockdown of NUPR1 Enhances the Sensitivity of Non-small-cell Lung Cancer Cells to Metformin by AKT Inhibition.

BACKGROUND/AIM: Metformin is a widely used drug for type 2 diabetes mellitus and has recently attracted broad attention for its therapeutic effects on many cancers. This study aimed to investigate the molecular mechanism of metformin's anticancer activity. MATERIALS AND METHODS: Cell viability was measured by MTT assay. Gene and protein expression levels were determined by reverse transcription-polymerase chain reaction and western blot analyses, respectively. RESULTS: Metformin and phenformin markedly induced NUPR1 expression in a dose- and time-dependent manner in H1299 non-small-cell lung cancer (NSCLC) cells. The silencing of NUPR1 in H1299 NSCLC cells enhanced cell sensitivity to metformin or ionizing radiation. Our previous report showed that metformin induces AKT serine/threonine kinase (AKT) activation in an activating transcription factor 4 (ATF4)-dependent manner and that the inhibition of AKT promotes cell sensitivity to metformin in H1299 NSCLC cells. Interestingly, ATF4-induced AKT activation in H1299 NSCLC cells treated with metformin was suppressed by the knockdown of NUPR1. CONCLUSION: Targeting NUPR1 could enhance the sensitivity of H1299 NSCLC cells to metformin by AKT inhibition.

3D printing of cell-laden visible light curable glycol chitosan bioink for bone tissue engineering.

Although chitosan is the second most abundant natural polymer on earth, with a wide range of biomaterial applications, its poor water solubility limits general printing process. We selected water-soluble methacrylated glycol chitosan (MeGC) as an alternative and prepared a MeGC-based MG-63 cell-laden bioink for 3D printing using a visible light curing system. Optimal cell-laden 3D printing of MeGC was completed at 3% using 12 µM of riboflavin as a photoinitiator under an irradiation for 70 s, a 26-gauge nozzle, a pneumatic pressure of 120 kPa, and a printing speed of 6 mm/s, as confirmed by printability, protein adsorption, cell viability, cell proliferation, and osteogenic capability. In addition, in vitro tests showed that MeGC-70 has a viability above 92%, a proliferation above 96%, and a hemolysis level below 2%. The results demonstrate the potential for MeGC-70 bioinks and 3D printed scaffolds to be used as patient-specific scaffolds for bone regeneration purposes.

Knockdown of YAP/TAZ sensitizes tamoxifen-resistant MCF7 breast cancer cells.

Although endocrine therapy with tamoxifen has improved survival in breast cancer patients, resistance to this therapy remains one of the major causes of breast cancer mortality. In the present study, we found that the expression level of YAP/TAZ in tamoxifen-resistant MCF7 (MCF7-TR) breast cancer cells was significantly increased compared with that in MCF7 cells. Knockdown of YAP/TAZ with siRNA sensitized MCF7-TR cells to tamoxifen. Furthermore, siRNA targeting PSAT1, a downstream effector of YAP/TAZ, enhanced sensitivity to tamoxifen in MCF7-TR cells. Additionally, mTORC1 activity and survivin expression were significantly decreased during cell death induced by combination treatment with YAP/TAZ or PSAT1 siRNA and tamoxifen. In conclusion, targeting the YAP/TAZ-PSAT1 axis could sensitize tamoxifen-resistant MCF7 breast cancer cells by modulating the mTORC1-survivin axis.

Suture Fiber Reinforcement of a 3D Printed Gelatin Scaffold for Its Potential Application in Soft Tissue Engineering.

Gelatin has excellent biological properties, but its poor physical properties are a major obstacle to its use as a biomaterial ink. These disadvantages not only worsen the printability of gelatin biomaterial ink, but also reduce the dimensional stability of its 3D scaffolds and limit its application in the tissue engineering field. Herein, biodegradable suture fibers were added into a gelatin biomaterial ink to improve the printability, mechanical strength, and dimensional stability of the 3D printed scaffolds. The suture fiber reinforced gelatin 3D scaffolds were fabricated using the thermo-responsive properties of gelatin under optimized 3D printing conditions (-10 °C cryogenic plate, 40-80 kPa pneumatic pressure, and 9 mm/s printing speed), and were crosslinked using EDC/NHS to maintain their 3D structures. Scanning electron microscopy images revealed that the morphologies of the 3D printed scaffolds maintained their 3D structure after crosslinking. The addition of 0.5% (w/v) of suture fibers increased the printing accuracy of the 3D printed scaffolds to 97%. The suture fibers also increased the mechanical strength of the 3D printed scaffolds by up to 6-fold, and the degradation rate could be controlled by the suture fiber content. In in vitro cell studies, DNA assay results showed that human dermal fibroblasts' proliferation rate of a 3D printed scaffold containing 0.5% suture fiber was 10% higher than that of a 3D printed scaffold without suture fibers after 14 days of culture. Interestingly, the supplement of suture fibers into gelatin biomaterial ink was able to minimize the cell-mediated contraction of the cell cultured 3D scaffolds over the cell culture period. These results show that advanced biomaterial inks can be developed by supplementing biodegradable fibers to improve the poor physical properties of natural polymer-based biomaterial inks.

The effects of the molecular weights of hyaluronic acid on the immune responses.

BACKGROUND: The molecular weight of hyaluronic acid (HyA) depends on the type of organ in the body. When HyA of the desired molecular weight is implanted into the human body for regeneration of damaged tissue, it is degraded by hyaluronidase in associated with an inflammatory response. This study sought to evaluate the effects of HyA molecular weight and concentration on pro- and anti-inflammatory responses in murine macrophages. METHODS: The structures and molecular weights of HyAs (LMW-10, MMW-100, MMW-500, and HMW-1,500) were confirmed by 1 H NMR and gel permeation chromatography (GPC), respectively. After treatment of murine macrophages with a low (10 µg/mL) or high (100 µg/mL) concentration of each molecular weight HyA, cells were stimulated with lipopolysaccharide (LPS) and changes in immune response in both LPS-stimulated and untreated macrophages were evaluated by assessing nitric oxide (NO) production, and analyzing expression of pro- and anti-inflammatory genes including by RT-PCR. RESULTS: Molecular weights of LMW-10, MMW-100, MMW-500, and HMW-1,500 were 13,241 ± 161, 96,531 ± 1,167, 512,657 ± 8,545, and 1,249,500 ± 37,477 Da, respectively. NO production by LPS-stimulated macrophages was decreased by increasing concentrations and molecular weights of HyA. At a high concentration of 100 µg/mL, HMW-1,500 reduced NO production in LPS-stimulated macrophages to about 45 %. Using NanoString technology, we also found that the immune-related genes TNF-α, IL-6, IL-1ß, TGF-ß1, IL-10, IL-11, CCL2, and Arg1 were specifically over-expressed in LPS-stimulated macrophages treated with various molecular weights of HyA. An RT-PCR analysis of gene expression showed that HMW-1,500 decreased expression of classically activated (M1) macrophage genes, such as TNF-α, IL-6, CCL2, and IL-1ß, in LPS-stimulated macrophages, whereas medium molecular-weight HyA (MMW-100 and MMW-500) instead increased expression levels of these genes. HMW-1,500 at a high concentration (100 µg/mL) significantly decreased expression of pro-inflammatory genes in LPS-stimulated macrophages. Expression of genes associated with anti-inflammatory responses (M2 phenotype), such as TGF-ß1, IL-10, IL-11, and Arg1, were increased by high concentrations of MMW-500 and HMW-1,500 in LPS-stimulated macrophages. CONCLUSIONS: High molecular-weight HyA (i.e., > 1,250 kDa) inhibits pro-inflammatory responses in LPS-stimulated macrophages and induces anti-inflammatory responses in a concentration dependent manner.

Peptide 18-4/chlorin e6-conjugated polyhedral oligomeric silsesquioxane nanoparticles for targeted photodynamic therapy of breast cancer.

Chlorin e6 (Ce6), with its high phototoxic potential, has wide applications in photodynamic therapy (PDT) for many human diseases. However, poor cancer cell localization of Ce6 has limited its direct application for PDT. Here, we developed cancer-targeting peptide p 18-4/chlorin e6 (Ce6)-conjugated polyhedral oligomeric silsesquioxane (PPC) nanoparticles for improving the targeting ability of Ce6 to breast cancer cells, thereby enhancing PDT efficacy. The synthesized PPC nanoparticles exhibited a spherical shape with an average diameter of 127.2 ± 11.3 nm in aqueous solution. Compared with free Ce6, the immobilization of p 18-4 enhanced the in vitro cellular uptake and targeting ability of PPC nanoparticles in breast cancer cell line MDA-MB-231. In addition, the intracellular uptake of PPC nanoparticles in MDA-MB-231 cells was dramatically increased compared with other cancer cells, indicating an obvious targeting ability of PPC nanoparticles on breast cancer cells. Upon light irradiation, PPC nanoparticles revealed significantly improved phototoxicity to MDA-MB-231 cells, mainly due to apoptotic cell death. In vivo PDT study suggested that PPC nanoparticles exhibited increased retention in tumor tissues and effectively inhibited the growth of MDA-MB-231 tumors in a target-specific manner. Overall, these results indicate that PPC nanoparticles are highly effective PDT agents for breast cancer therapy.

Ionizing radiation attracts tumor targeting and apoptosis by radiotropic lysyl oxidase traceable nanoparticles.

Lysyl oxidase (LOX) is a cell-secreted amine oxidase that crosslinks collagen and elastin in extracellular microenvironment. LOX-traceable nanoparticles (LOXab-NPs) consisting of LOX antibodies (LOXab) and paclitaxel, can accumulate at high concentrations at radiation-treated target sites, as a tumor-targeting drug carrier for chemotherapy. Tumor-targeting and anticancer effects of PLGA based LOXab-NPs in vitro and in vivo were evaluated at radiation-targeted site. In the in vivo A549 lung carcinoma xenograft model, we showed highly specific tumor targeting (above 7.0 times higher) of LOXab-NPs on irradiated tumors. Notably, systemically administered NPs delayed tumor growth, reducing tumor volumes by more than 2 times compared with non-irradiated groups (222% vs. >500%) over 2 weeks. Radiotropic LOXab-NPs can serve as chemotherapeutic vehicles for combined targeted chemo-radiotherapy in clinical oncology.

Effect of cross-linking on the dimensional stability and biocompatibility of a tailored 3D-bioprinted gelatin scaffold.

Biocompatible and biodegradable gelatin is a good candidate bioink for use in 3D bioprinting technologies, but viscous gelatin solution has a low printability. In order to improve the poor printability of gelatin, we optimized the rheological properties of gelatin solution. 3D gelatin scaffolds were then cross-linked using physical or chemical methods to maintain the 3D structure. The physicochemical and biological differences between the two types of cross-linked gelatin scaffolds were studied. Scanning electron microscopy images revealed that the morphologies of the resulting cross-linked 3D scaffolds maintained their structural stabilities. The physically cross-linked 3D scaffolds maintained their surface sizes without a significant decrease (less than a 3% reduction in the surface size was observed) after cross-linking. To evaluate the differences in cell affinity by two types of cross-linking method, human dermal fibroblasts cultured on the cross-linked 3D scaffolds. After 14 days of culturing, DNA assays showed that the cell proliferation rate of the physically cross-linked 3D scaffold was 44% higher than that of the chemically cross-linked 3D scaffold. In conclusion, the optimized physically cross-linked 3D scaffold retained its surface size without significant decreases after cross-linking, as required by 3D-printed patient-specific tissue engineered customized scaffolds, despite the use of water-soluble gelatin hydrogels.

3D Bioprinting Technologies for Tissue Engineering Applications.

Three-dimensional (3D) printing (rapid prototyping or additive manufacturing) technologies have received significant attention in various fields over the past several decades. Tissue engineering applications of 3D bioprinting, in particular, have attracted the attention of many researchers. 3D scaffolds produced by the 3D bioprinting of biomaterials (bio-inks) enable the regeneration and restoration of various tissues and organs. These 3D bioprinting techniques are useful for fabricating scaffolds for biomedical and regenerative medicine and tissue engineering applications, permitting rapid manufacture with high-precision and control over size, porosity, and shape. In this review, we introduce a variety of tissue engineering applications to create bones, vascular, skin, cartilage, and neural structures using a variety of 3D bioprinting techniques.

Chitosan for Tissue Engineering.

Chitosan, a deacetylated chitin, is one of the few natural polymers similar to glycosaminoglycans (GAGs) widely distributed throughout connective tissues. It has been believed that the excellent biocompatibility of chitosan is largely attributed to this structural similarity. Chitosan is also known to possess biodegradability, antimicrobial activity and low toxicity and immunogenicity which are essential for scaffolds. In addition, the existence of free amine groups in its backbone chain enables further chemical modifications to create the additional biomedical functionality. For these reasons, chitosan has found a tremendous variety of biomedical applications in recent years. This chapter introduces the basic contents of chitosan and discusses its applications to artificial skin, artificial bone, and artificial cartilage in tissue engineering purpose.

Fabrication of polytetrafluoroethylene nanofibrous membranes for guided bone regeneration.

In this study, we first prepared the precursor polytetrafluoroethylene (PTFE)/poly(ethylene oxide) (PEO) nanofibrous membranes by electrospinning with different PTFE/PEO weight ratios. These membranes exhibited three-dimensional interconnected pore structures. The average diameter of the precursor nanofibres decreased with increased PTFE contents from 633 ± 34 nm (PTFE/PEO weight ratio of 5 : 1) to 555 ± 63 nm (PTFE/PEO weight ratio of 7 : 1) because of the decrease in solution viscosity. Then, the precursor membranes were sintered with different temperatures to obtain the PTFE nanofibrous membranes, resulting in the average diameter of the nanofibres increasing from 633 ± 34 nm to 947 ± 78 nm with the increase in sintering temperature; consequently, the membrane became more compact. This compaction caused a decrease in porosity from 76.5 ± 2.9% to 69.1 ± 2.6% and an increase in water contact angle from 94.1 ± 4.2° to 143.3 ± 3.5°. In addition, the mechanical properties of the PTFE nanofibrous membranes increased with increasing sintering temperature. Cytocompatibility test results revealed that the PTFE350 membrane, which was sintered at 350 °C, promoted the proliferation and differentiation of MC3T3-E1 cells more rapidly than other membrane types. These results suggested that the PTFE nanofibrous membranes could be ideal biomaterials in tissue engineering for bone regeneration.

Substance-P and transforming growth factor-ß in chitosan microparticle-pluronic hydrogel accelerates regenerative wound repair of skin injury by local ionizing radiation.

Clinical irradiation therapy for cancer could increase the risk of localized wound complications. This study was conducted to evaluate the potential use of a chitosan microparticle-pluronic F127 (CSMP-PF) hydrogel complex containing bioactive molecules, substance P and transforming growth factor-ß1, to regeneratively repair skin damaged by local ionizing radiation (IR). The BALB/c/bkl mice were locally irradiated to their limbs with a single 40 Gy dose of Co-60 γ rays to induce a skin injury. The morphological characteristics of the chitosan microparticles were analysed by scanning electron microscopy. The amounts of bioactive molecules taken up and released by the CSMP-PF hydrogel complex were measured. Haematoxylin and eosin staining of IR-damaged skin showed acanthosis and hyperkeratosis in the epidermis; and damage to hair follicles/skin appendages and adipose tissue, as well as panniculus carnosus, in the dermis. Injection of the CSMP-PF hydrogel complex into IR-damaged skin resulted in skin repair, suggesting that the complex has potential for use in the regenerative repair of IR-damaged skin.

Beneficial effect of aligned nanofiber scaffolds with electrical conductivity for the directional guide of cells.

Conducting polymer-based scaffolds receive biological and electrical signals from the extracellular matrix (ECM) or peripheral cells, thereby promoting cell growth and differentiation. Chitin, a natural polymer, is widely used as a scaffold because it is biocompatible, biodegradable, and nontoxic. In this study, we used an electrospinning technique to fabricate conductive scaffolds from aligned chitin/polyaniline (Chi/PANi) nanofibers for the directional guidance of cells. Pure chitin and random and aligned Chi/PANi nanofiber scaffolds were characterized using field emission scanning electron microscope (FE-SEM) and by assessing wettability, mechanical properties, and electrical conductivity. The diameters of aligned Chi/PANi nanofibers were confirmed to be smaller than those of pure chitin and random nanofibers owing to electrostatic forces and stretching produced by rotational forces of the drum collector. The electrical conductivity of aligned Chi/PANi nanofiber scaffolds was ~91% higher than that of random nanofibers. We also studied the viability of human dermal fibroblasts (HDFs) cultured on Chi/PANi nanofiber scaffolds in vitro using a CCK-8 assay, and found that cell viability on the aligned Chi/PANi nanofiber scaffolds was ~2.1-fold higher than that on random Chi/PANi nanofiber scaffolds after 7 days of culture. Moreover, cells on aligned nanofiber scaffolds spread in the direction of the aligned nanofibers (bipolar), whereas cells on the random nanofibers showed no spreading (6 h of culture) or multipolar patterns (7 days of culture). These results suggest that aligned Chi/PANi nanofiber scaffolds with conductivity exert effects that could improve survival and proliferation of cells with directionality.