Investigation of the optimal light parameters for photobiomodulation to induce osteogenic differentiation of the human bone marrow stem cell and human umbilical vein endothelial cell co-culture.

Bones have an important role in the human body with their complex nature. Mesenchymal stem cells and endothelial cells together support their unique and complex nature. Photobiomodulation (PBM) is a promising method that provides cell proliferation, osteogenic differentiation, and bone regeneration. However, there are still unknowns in the mechanism of osteogenic differentiation induced by PBM. The main aim of the study is to understand the molecular mechanism of PBM at 655 and 808 nm of wavelengths and identify the most effective energy densities of both wavelengths for osteogenic differentiation. The effect of PBM on osteogenic differentiation of Human Bone Marrow Stem Cell (hBMSC) and Human Umbilical Vein Endothelial Cell (HUVEC) co-culture was examined at 1, 3, and 5 J/cm2 energy densities of red and near-infrared light through different analysis such as cell viability, scratch assay, intracellular reactive oxygen species production, and ATP synthesis, nitric oxide release, temperature monitoring, and osteogenic differentiation analyses. Even though all PBM-treated groups exhibited better results compared to the control group, 5 J/cm2 energy density induced faster cell proliferation and migration at both wavelengths. The increases in ATP and NO levels as signaling molecules, and the increases in DNA, ALPase, and calcium contents as osteogenic markers were higher in the groups treated with 5 J/cm2 energy density at both wavelengths. Only a slight change was obtained in the level of intracellular ROS after any light applications. It can be concluded that NO release has a very important role together with ATP production in PBM therapy to trigger DNA synthesis, ALPase activity, and mineralization for osteogenic differentiation of the hBMSC and HUVEC co-culture at 655 and 808 nm of wavelengths.

Artificial oxygen carriers in organ preservation: Dose dependency in a rat model of ex-vivo normothermic kidney perfusion.

INTRODUCTION: Organ preservation through ex-vivo normothermic perfusion (EVNP) with albumin-derived perfluorocarbon-based artificial oxygen carriers (A-AOCs) consisting of albumin-derived perfluorodecalin-filled nanocapsules prior to transplantation would be a promising approach to avoid hypoxic tissue injury during organ storage. METHODS: The kidneys of 16 rats underwent EVNP for 2 h with plasma-like solution (5% bovine serum albumin, Ringer-Saline, inulin) with or without A-AOCs in different volume fractions (0%, 2%, 4%, or 8%). Cell death was determined using TdT-mediated dUTP-biotin nick end labeling (TUNEL). Aspartate transaminase (AST) activity in both perfusate and urine as well as the glomerular filtration rate (GFR) were determined. The hypoxia inducible factors 1α and 2α (HIF-1α und -2α) were quantified in tissue homogenates. RESULTS: GFR was substantially decreased in the presence of 0%, 2%, and 8% A-AOC but not of 4%. In accordance, hypoxia-mediated cell death, as indicated by both AST activity and TUNEL-positive cells, was significantly decreased in the 4% group compared to the control group. The stabilization of HIF-1α and 2α decreased with 4% and 8% but not with 2% A-AOCs. CONCLUSION: The dosage of 4% A-AOCs in EVNP was most effective in maintaining the physiological renal function.

Role of functionalized self-assembled peptide hydrogels in in vitro vasculogenesis.

Fabrication of vascularized tissue constructs plays an integral role in creating clinically relevant tissues. Scaffold materials should be sufficiently vascularized to mimic functional and complex native tissues. Herein, we report the development of bioactive and biomimetic self-assembled peptide (SAP) hydrogels that allow the rapid formation of a vascular structure in vitro. The KLDLKLDLKLDL (KLD peptide) SAP was functionalized with laminin derived peptides IKVAV (V1) and YIGSR (V2) through direct coupling to mimic the natural extracellular matrix (ECM) and human umbilical endothelial cells (HUVECs) and mesenchymal stem cells (MSCs) cultured in 0.5% and 1% SAP hydrogels organized into vascularized structures. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images proved the molecular integration of the nanofibrous structure in SAP hydrogels. The stability of SAP hydrogels was confirmed by rheological and degradation measurements. Bioactive peptide scaffolds enhanced significantly HUVEC/hMSC proliferation depicted by MTT analysis compared to KLD. Furthermore, the real time quantitative polymerase chain reaction (rt-PCR) was performed to analyse vascular gene expressions such as platelet/endothelial cell adhesion molecule-1 (PECAM-1), von Willebrand factor (vWF), and vascular endothelial cadherin (VE-cadherin). The results indicated that the KLD-V2 hydrogel significantly induced vasculogenesis in hMSC/HUVEC co-culture compared to KLD-V1, Biogelx and KLD because YIGSR in KLD-V2 promoted cell population and ECM secretion by the interaction with cells and increased vasculogenesis. Overall, the designed SAP hydrogel represents an effective scaffold for vascularization of tissue constructs with useful tissue engineering applications.

Evaluation of efficacy of non-thermal atmospheric pressure plasma in treatment of periodontitis: a randomized controlled clinical trial.

OBJECTIVES: In this clinical study, we aim to evaluate the effectiveness of non-thermal atmospheric pressure plasma (NAPP), which is a novel procedure used in periodontal pocket decontamination adjunctive to non-surgical periodontal treatment (NSPT). METHODS: The study included 25 systemically healthy periodontitis patients. In the split-mouth design, NAPP application into the pockets, in addition to NSPT, was performed. Clinical periodontal data, gingival crevicular fluid, and subgingival plaque samples of patients were taken before and during the first and third months of treatment. Biochemical assays were conducted using enzyme-linked immunosorbent assay. Analysis of bacteria was performed with polymerase chain reaction method. RESULTS: There was more clinical attachment level (CAL) gain in the 3rd month in the test group (deep pockets: 3.90 mm, pockets ≥ 5 mm: 2.72 mm) compared to the control group (deep pockets: 3.40 mm, pockets ≥ 5 mm: 2.58 mm) (p < 0.05), but no significant difference between groups in CAL. Clinical periodontal parameters improved in both study groups (p < 0.05). However, the gingival index (GI) and the bleeding on probing (BOP) rate decreased more in the test group (GI: 0.55, BOP: 9.48%, and GI: 0.38, BOP: 8.46% in the 1st and 3rd months, respectively) compared to the control group (GI: 0.68, BOP: 13.43%, and GI: 0.52, BOP: 14.58%) (p < 0.05). In addition, there was no significant difference in probing depth and biochemical markers between groups (p > 0.05). It was observed that NAPP reduced the number of bacteria more than the control group in the 1st and 3rd months. CONCLUSIONS: It was seen that the single-time NAPP application concurrent with NSPT provided additional CAL gain, elimination of putative periodontopathogens and reduced their recolonization. Longitudinal studies with larger population and longer time are required. CLINICAL RELEVANCE: NSPT is an effective method for the treatment of periodontitis but bacteria recolonization that causes recurrence of the periodontal disease occurs within a short period. NAPP can reduce the recurrence of periodontal disease by providing better bacterial elimination and should, therefore, be used in maintenance of periodontitis.

Time Dependence of Material Properties of Polyethylene Glycol Hydrogels Chain Extended with Short Hydroxy Acid Segments.

The objective of this work was to investigate the effect of chemical composition and segment number (n) on gelation, stiffness, and degradation of hydroxy acid-chain-extended star polyethylene glycol acrylate (SPEXA) gels. The hydroxy acids included glycolide (G,), L-lactide (L), p-dioxanone (D) and -caprolactone (C). Chain-extension generated water soluble macromers with faster gelation rates, lower sol fractions, higher compressive moduli, and a wide-ranging degradation times when crosslinked into a hydrogel. SPEGA gels with the highest fraction of inter-molecular crosslinks had the most increase in compressive modulus with n whereas SPELA and SPECA had the lowest increase in modulus. SPEXA gels exhibited a wide range of degradation times from a few days for SPEGA to a few weeks for SPELA, a few months for SPEDA, and many months for SPECA. Marrow stromal cells and endothelial progenitor cells had the highest expression of vasculogenic markers when co-encapsulated in the faster degrading SPELA gel.

Collagen binding and mimetic peptide-functionalized self-assembled peptide hydrogel enhance chondrogenic differentiation of human mesenchymal stem cells.

The avascular structure and low cell migration to the damaged area due to the low number of cells do not allow spontaneous repair of the articular cartilage tissue. Therefore, functional scaffolds obtained from biomaterials are used for the regeneration of cartilage tissue. Here, we functionalized one of the self-assembling peptide (SAP) scaffolds KLD (KLDLKLDLKLDL) with short bioactive motifs, which are the α1 chain of type II collagen binding peptide WYRGRL (C1) and the triple helical collagen mimetic peptide GFOGER (C2) by direct coupling. Our goal was to develop injectable functional SAP hydrogels with proper mechanical characteristics that would improve chondrogenesis. Scanning electron microscopy (SEM) was used to observe the integration of peptide scaffold structure at the molecular level. To assure the stability of SAPs, the rheological characteristics and degradation profile of SAP hydrogels were assessed. The biochemical study of the DNA, glycosaminoglycan (GAG), and collagen content revealed that the developed bioactive SAP hydrogels greatly increased hMSCs proliferation compared with KLD scaffolds. Moreover, the addition of bioactive peptides to KLD dramatically increased the expression levels of important chondrogenic markers such as aggrecan, SOX-9, and collagen Type II as evaluated by real-time polymerase chain reaction (PCR). We showed that hMSC proliferation and chondrogenic differentiation were encouraged by the developed SAP scaffolds. Although the chondrogenic potentials of WYRGRL and GFOGER were previously investigated, no study compares the effect of the two peptides integrated into 3-D SAP hydrogels in chondrogenic differentiation. Our findings imply that these specifically created bioactive peptide scaffolds might help enhance cartilage tissue regeneration.

Prediction of the synergistic effect of antimicrobial peptides and antimicrobial agents via supervised machine learning.

BACKGROUND: Infectious diseases not only cause severe health problems but also burden the healthcare system. Therefore, the effective treatment of those diseases is crucial. Both conventional approaches, such as antimicrobial agents, and novel approaches, like antimicrobial peptides (AMPs), are used to treat infections. However, due to the drawbacks of current approaches, new solutions are still being investigated. One recent approach is the use of AMPs and antimicrobial agents in combination, but determining synergism is with a huge variety of AMPs time-consuming and requires multiple experimental studies. Machine learning (ML) algorithms are widely used to predict biological outcomes, particularly in the field of AMPs, but no previous research reported on predicting the synergistic effects of AMPs and antimicrobial agents. RESULTS: Several supervised ML models were implemented to accurately predict the synergistic effect of AMPs and antimicrobial agents. The results demonstrated that the hyperparameter-optimized Light Gradient Boosted Machine Classifier (oLGBMC) yielded the best test accuracy of 76.92% for predicting the synergistic effect. Besides, the feature importance analysis reveals that the target microbial species, the minimum inhibitory concentrations (MICs) of the AMP and the antimicrobial agents, and the used antimicrobial agent were the most important features for the prediction of synergistic effect, which aligns with recent experimental studies in the literature. CONCLUSION: This study reveals that ML algorithms can predict the synergistic activity of two different antimicrobial agents without the need for complex and time-consuming experimental procedures. The implications support that the ML models may not only reduce the experimental cost but also provide validation of experimental procedures.

Nanostructure formation and transition from surface to bulk degradation in polyethylene glycol gels chain-extended with short hydroxy acid segments.

Degradable, in situ gelling, inert hydrogels with tunable properties are very attractive as a matrix for cell encapsulation and delivery to the site of regeneration. Cell delivery is generally limited by the toxicity of gelation and degradation reactions. The objective of this work was to investigate by simulation and experimental measurement gelation kinetics and degradation rate of star acrylated polyethylene glycol (PEG) macromonomers chain-extended with short hydroxy acid (HA) segments (SPEXA) as a function of HA monomer type and number of HA repeat units. HA monomers included least hydrophobic glycolide (G), lactide (L), p-dioxanone (D), and most hydrophobic ε-caprolactone (C). Chain extension of PEG with short HA segments resulted in micelle formation for all HA types. There was a significant decrease in gelation time of SPEXA precursor solutions with HA chain-extension for all HA types due to micelle formation, consistent with the simulated increase in acrylate-acrylate (Ac-Ac) and Ac-initiator integration numbers. The hydrolysis rate of SPEXA hydrogels was strongly dependent on HA type and number of HA repeat units. SPEXA gels chain-extended with the least hydrophobic glycolide completely degraded within days, lactide within weeks, and p-dioxanone and ε-caprolactone degraded within months. The wide range of degradation rates observed for SPEXA gels can be explained by large differences in equilibrium water content of the micelles for different HA monomer types. A biphasic relationship between HA segment length and gel degradation rate was observed for all HA monomers, which was related to the transition from surface (controlled by HA segment length) to bulk (controlled by micelle equilibrium water content) hydrolysis within the micelle phase. To our knowledge, this is the first report on transition from surface to bulk degradation at the nanoscale in hydrogels.

Effect of antimicrobial peptide conjugated surgical sutures on multiple drug-resistant microorganisms.

Surgical site infections are commonly encountered as a risk factor in clinics that increase the morbidity of a patient after a surgical operation. Surgical sutures are one of the leading factor for the formation of surgical site infections that induce bacterial colonization by their broad surface area. Current strategies to overcome with surgical site infections consist utilization of antibiotic agent coatings such as triclosan. However, the significant increase in antibiotic resistance majorly decreases their efficiency against recalcitrant pathogens such as; Pseudomonas aeruginosa and Staphylococcus aureus. Therefore, the development of a multi drug-resistant antimicrobial suture without any cytotoxic effect to combat surgical site infections is vital. Antimicrobial peptides are the first defense line which has a broad range of spectrum against Gram-positive, and Gram-negative bacteria and even viruses. In addition, antimicrobial peptides have a rapid killing mechanism which is enhanced by membrane disruption and inhibition of functional proteins in pathogens without the development of antimicrobial resistance. In the scope of the current study, the antimicrobial effect of antimicrobial peptide conjugated poly (glycolic acid-co-caprolactone) (PGCL) sutures were investigated against P. aeruginosa and methicillin-resistant S. aureus (MRSA) strains by using antimicrobial peptide sequences of KRFRIRVRV-NH2, RWRWRWRW-NH2 and their dual combination (1:1). In addition, in vitro wound scratch assays were performed to evaluate the effect of antimicrobial peptide conjugated sutures on keratinocyte cell lines. Our results indicated that antimicrobial peptide modified sutures could be a potential novel medical device to overcome surgical site infections by the superior acceleration of wound healing.

Photobiomodulation therapy at red and near-infrared wavelengths for osteogenic differentiation in the scaffold-free microtissues.

One of the novel strategies for bone tissue regeneration is photobiomodulation (PBM) which depends on the red and near-infrared light absorption by mitochondria and may trigger bone tissue regeneration via the production of intracellular ROS and ATP, NO release, etc. It is also important to identify the changes in those signal molecule levels in an in vivo mimicking platform such as 3-Dimensional (3D) Scaffold Free Microtissues (SFMs) that may serve more natural osteogenic differentiation responses to PBM. Herein, we aimed to increase the osteogenic differentiation capability of the co-culture of Human Bone Marrow Stem Cells (hBMSC) and Human Umbilical Vein Endothelial Cells (HUVECs) on 3D SFMs by triple light treatment at 655 and 808-nm of wavelengths with the energy densities of 1, 3, and 5 J/cm2. We performed the analysis of cell viability, diameter measurements of SFMs, intracellular ROS production, NO release, ATP activity, temperature measurements, DNA content, ALPase activity, calcium content, and relative gene expressions of ALP, Collagen, and Osteopontin by qRT-PCR. It was found that both wavelengths were effective in terms of the viability of SFMs. 1 and 5 J/cm2 energy densities of both wavelengths increased the SFM diameter with significant changes in intracellular ROS, ATP, and NO levels compared to the control group. We concluded that PBM therapy was successful to induce osteogenesis. 1 J/cm2 at 655 nm of wavelength and 5 J/cm2 at 808 nm of wavelength were the most effective energy densities for osteogenic differentiation on SFMs with triple light treatment.

Synergistic effects of integrin binding peptide (RGD) and photobiomodulation therapies on bone-like microtissues to enhance osteogenic differentiation.

Bone tissue engineering aims to diversify and enhance the strategies for bone regeneration to overcome bone-related health problems. Bone mimetic peptides such as Gly-Arg-Gly-Asp-Ser (RGD) are useful tools for osteogenic differentiation. Similarly, photobiomodulation (PBM) at 600-800 nm of wavelength range improves bone tissue healing via the production of intracellular reactive oxygen species (ROS), ATP synthesis, and nitric oxide (NO) release. Besides, traditional monolayer cell culture models have limited conditions to exhibit the details of a mechanism such as a peptide or PBM therapy. However, scaffold-free microtissues (SFMs) can mimic a tissue more properly and be an efficient way to understand the mechanism of therapy via cell-cell interaction. Thus, the synergistic effects of RGD peptide (1 mM) and PBM applications (1 J/cm2 energy density at 655 nm of wavelength and 5 J/cm2 energy density at 808 nm of wavelength) were evaluated on SFMs formed with the co-culture of Human Bone Marrow Stem Cells (hBMSC) and Human Umbilical Vein Endothelial Cells (HUVEC) for osteogenic differentiation. Cell viability assays, mechanistic analysis, and the evaluation of osteogenic differentiation markers were performed. Combined therapies of RGD and PBM were more successful to induce osteogenic differentiation than single therapies. Especially, RGD + PBM at 655 nm group exhibited a higher capability of osteogenic differentiation via ROS production, ATP synthesis, and NO release. It can be concluded that the concomitant use of RGD and PBM may enhance bone regeneration and become a promising therapeutic tool to heal bone-related problems in clinics.

Comparison of Particulate, Block and Putty Forms of ß-tricalcium Phosphate-Based Synthetic Bone Grafts on Rat Calvarium Model.

Purpose: Bone augmentation is a necessity for atrophied alveolar ridge prior to dental implant placement. Various bone graft types and forms with different characteristics are available in the market for alveolar augmentation. Beta tricalcium phosphate (ß-TCP) is a synthetic biomaterial known as the oldest type of calcium phosphate. Studies comparing particulate, block or putty grafts are very limited. The aim of this study was to compare the particulate, block and putty forms of the same ß-TCP bone graft and analyze the efficiency in critical size calvarium defects. Material and Methods: Twenty male Wistar-Albino rats were employed for the study. Four bicortical bone defects with 5 mm diameter were created on each rat calvarium, and three defects were filled with particulate, block or putty ß-TCP graft and one defect was left empty. The animals were killed after 8 weeks. New bone formation, residual graft, loose connective tissue, condensed mesenchyme, alkaline phosphatase, proliferating cell nuclear antigen, osteocalcin were measured on the specimens. Results: Compared to block and putty forms, significantly higher new bone formation and least residual graft were observed in the particulate graft group. The residual graft was significantly higher in the block graft group than both the particulate and the putty groups. The cellular immunoreactivity of the samples in the particulate graft group was significantly higher. There was no significant difference between putty and block graft groups. Conclusion: Bone regeneration is significantly affected by the form of ß-TCP bone graft, and the particulate form was the most successful in our study.

Effect of Integrin Binding Peptide on Vascularization of Scaffold-Free Microtissue Spheroids.

BACKGROUND: Three-dimensional (3D) biomimetic models via various approaches can be used by therapeutic applications of tissue engineering. Creating an optimal vascular microenvironment in 3D model that mimics the extracellular matrix (ECM) and providing an adequate blood supply for the survival of cell transplants are major challenge that need to be overcome in tissue regeneration. However, currently available scaffolds-depended approaches fail to mimic essential functions of natural ECM. Scaffold-free microtissues (SFMs) can successfully overcome some of the major challenges caused by scaffold biomaterials such as low cell viability and high cost. METHODS: Herein, we investigated the effect of soluble integrin binding peptide of arginine-glycine-aspartic acid (RGD) on vascularization of SFM spheroids of human umbilical vein endothelial cells. In vitro-fabricated microtissue spheroids were constructed and cultivated in 0 mM, 1 mM, 2 mM, and 4 mM of RGD peptide. The dimensions and viability of SFMs were measured. RESULTS: Maximum dimension and cell viability observed in 2 mM RGD containing SFM. Vascular gene expression of 2 mM RGD containing SFM were higher than other groups, while 4 mM RGD containing SFM expressed minimum vascularization related genes. Immunofluorescent staining results indicating that platelet/endothelial cell adhesion molecule and vascular endothelial growth factor protein expression of 2 mM RGD containing SFM was higher compared to other groups. CONCLUSION: Collectively, these findings demonstrate that SFM spheroids can be successfully vascularized in determined concentration of RGD peptide containing media. Also, soluble RGD incorporated SFMs can be used as an optimal environment for successful prevascularization strategies.

Antibacterial activity of antimicrobial peptide-conjugated nanofibrous membranes.

Antimicrobial peptides (AMPs) are considered as novel potential alternatives to antibiotics against increasing number of multi drug resistant (MDR) pathogens. Although AMPs have shown strong antimicrobial activity against gram-negative or gram-positive microorganisms, AMP conjugated biomaterials that are effective against MDR microorganisms are yet to be developed. Herein, the potential use of (RWRWRWRW)-NH2 (AMP-1) and KRFRIRVRV-NH2 (AMP-2) peptide conjugated electrospun polylactic-co-glycolic-acid (PLGA) nanofibers (NFs) fabricated and their antimicrobial effect by themselves and in their dual combination (1:1) were evaluated on P. aeruginosa and methicillin-resistant S. aureus (MRSA). Those AMP conjugated NFs did not inhibit proliferation of keratinocytes. These results suggest that AMP conjugated NF, which has multiple biological activities, would be a promising candidate as a wound dressing material.

The effect of indocyanine green-based photodynamic therapy on healthy fibroblast and keratinocyte cells.

BACKGROUND: Photodynamic therapy is a promising invention to treat infections and cancer where conventional treatments are insufficient and have many side effects. Photodynamic therapy is mainly emphasized as having minimal side effects on healthy cells during local applications, even so photosensitizer can accumulate in any cell and unwanted deaths may occur upon irradiation. This study focused on the degree of photodynamic action with indocyanine green against healthy cells, when it has phototoxic effects on pathogens. METHODS: Healthy mouse skin fibroblast and human skin keratinocyte cells were exposed to energy densities of 84 and 252 J/cm2 with 4, 10, 25, 50,100, 125 and 150 µg/mL indocyanine green which have efficiently killed gram-positive and gram-negative pathogens. Cell Viability, Lipid Peroxidation and Live/Dead Cell Staining analysis were performed to assess the phototoxicity with defined parameters on the healthy cells. RESULTS: 84 J/cm2 energy density was quite safe for keratinocytes with indocyanine green concentrations ranging from 4 to 125 µg/mL. When 252 J/cm2 energy density was used, most of the keratinocytes were damaged with any photosensitizer concentration. Fibroblasts only tolerate these energy densities together with 4 and 10 µg/mL indocyanine green. Increasing photosensitizer concentrations resulted in high phototoxic effect on them. CONCLUSION: Photodynamic therapy applications, which destroy pathogens, may also kill healthy eukaryotic cells. While some energy densities are safe, but others cause serious mortality rate on fibroblasts and keratinocytes. Therefore, harm to healthy cells related to photodynamic therapy parameters should be minimized by the optimization of energy densities and photosensitizer concentration properly.

Enhanced osteogenesis of human mesenchymal stem cells by self-assembled peptide hydrogel functionalized with glutamic acid templated peptides.

Self-assembling peptide (SAP) hydrogel has been shown to be an excellent biological material for three-dimensional cell culture and stimulatie cell migration and differentiation into the scaffold, as well as for repairing bone tissue defects. Herein, we designed one of the SAP scaffolds KLD (KLDLKLDLKLDL) through direct coupling to short bioactive motif O1 (EEGGC) and O2 (EEEEE) of which bioactivity on osteogenic differentiation was previously demonstrated and self-assembled in different concentrations (0.5%, 1%, and 2%). Our aim was to enhance osteogenesis and biomineralization of injectable SAP hydrogels with controlled mechanical properties so that the peptide hydrogel also becomes capable of being injected to bone defects. The molecular integration of the nanofibrous peptide scaffolds was observed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The rheological properties and degradation profile of SAP hydrogels were evaluated to ensure stability of SAPs. Compared with pure KLD scaffold, we found that these designed bioactive peptide scaffolds significantly promoted hMSCs proliferation depicted by biochemical analysis of alkaline phosphatase (ALP) activity, total calcium deposition. Moreover, key osteogenic markers of ALP activity, collagen type I (COL-1), osteopontin (OP), and osteocalcin (OCN) expression levels determined by real-time polymerase chain reaction (PCR) and immunofluorescence analysis were also significantly increased with the addition of glutamic acid residues to KLD. We demonstrated that the designed SAP scaffolds promoted the proliferation and osteogenic differentiation of hMSCs. Our results suggest that these designed bioactive peptide scaffolds may be useful for promoting bone tissue regeneration.

Guiding neural extensions of PC12 cells on carbon nanotube tracks dielectrophoretically formed in poly(ethylene glycol) dimethacrylate.

The PC12 cell line has been widely used as an in vitro model for studying neuronal differentiation and identifying the factors affecting the process. It has the ability to differentiate in the presence of nerve growth factor (NGF), resulting in neural extensions called dendrites and axons. In this study, first the impact of randomly distributed multi-walled carbon nanotubes (MWCNTs) in poly(ethylene glycol) dimethacrylate (PEGDMA) on PC12 cell differentiation was investigated in terms of neurite length, number of neurite per cell and differentiation marker gene expression profile. Then, dielectrophoretically aligned MWCNTs in PEGDMA was used to guide and support the neuronal differentiation of PC12 cells in the presence of NGF. The method is expected to be useful in revealing the nanotopographical role in fundamental studies and understanding of nanotopographical effects for biomedical applications on nerve regeneration.

Accelerated mineralization on nanofibers via non-thermal atmospheric plasma assisted glutamic acid templated peptide conjugation.

Surface modification by non-thermal atmospheric plasma (NTAP) treatment can produce significantly higher carboxylic groups on the nanofibers (NF) surface, which potentially can increase biomineralization of NF via promoting glutamic acid (GLU) templated peptide conjugation. Herein, electrospun poly(lactide-co-glycolide) (PLGA) scaffolds were treated with NTAP and conjugated with GLU peptide followed by incubation in simulated body fluids for mineralization. The effect of NTAP treatment and GLU peptide conjugation on mineralization, surface wettability and roughness were investigated. The results showed that NTAP treatment significantly increased GLU peptide conjugation which consequently enhanced mineralization and mechanical properties of NTAP treated and peptide conjugated NF (GLU-pNF) compared to neat PLGA NF, NTAP treated NF (pNF) and GLU peptide conjugated NF (GLU-NF). The effect of surface modification on human bone marrow derived mesenchymal stem cells adhesion, proliferation and morphology was evaluated by cell proliferation assay and fluorescent microscopy. Results demonstrated that cellular adhesion and proliferation were significantly higher on GLU-pNF compared to NF, pNF and GLU-NF. In summary, NTAP treatment could be a promising modification technique to induce biomimetic peptide conjugation and biomineralization for bone tissue engineering applications.

Material and regenerative properties of an osteon-mimetic cortical bone-like scaffold.

The objective of this work was to fabricate a rigid, resorbable and osteoconductive scaffold by mimicking the hierarchical structure of the cortical bone. Aligned peptide-functionalize nanofiber microsheets were generated with calcium phosphate (CaP) content similar to that of the natural cortical bone. Next, the CaP-rich fibrous microsheets were wrapped around a microneedle to form a laminated microtube mimicking the structure of an osteon. Then, a set of the osteon-mimetic microtubes were assembled around a solid rod and the assembly was annealed to fuse the microtubes and form a shell. Next, an array of circular microholes were drilled on the outer surface of the shell to generate a cortical bone-like scaffold with an interconnected network of Haversian- and Volkmann-like microcanals. The CaP content, porosity and density of the bone-mimetic microsheets were 240 wt%, 8% and 1.9 g/ml, respectively, which were close to that of natural cortical bone. The interconnected network of microcanals in the fused microtubes increased permeability of a model protein in the scaffold. The cortical scaffold induced osteogenesis and vasculogenesis in the absence of bone morphogenetic proteins upon seeding with human mesenchymal stem cells and endothelial colony-forming cells. The localized and timed-release of morphogenetic factors significantly increased the extent of osteogenic and vasculogenic differentiation of human mesenchymal stem cells and endothelial colony-forming cells in the cortical scaffold. The cortical bone-mimetic nature of the cellular construct provided balanced rigidity, resorption rate, osteoconductivity and nutrient diffusivity to support vascularization and osteogenesis.