In this study, the surface of poly(epsilon-caprolactone) (PCL) scaffold was modified by chitosan (CS) in order to enhance its cell affinity and biocompatibility. It is demonstrated by scanning electronic microscopy (SEM) that when 0.5-2.0 wt% chitosan solutions are used to modify the PCL scaffold, the amount of adhesion of the fibroblasts on the chitosan-modified PCL scaffolds dramatically increase when compared to the control after 7 days cell culture. The results indicate that the chitosan-modified PCL scaffolds are more favorable for cell proliferation by improving the scaffold biocompatibility. The improvement may be helpful for the extensive applications of PCL scaffold in heart valve and blood vessel tissue engineering.

In order to develop scaffolds with improved biocompatibility for cell culture, hybrid scaffolds were fabricated by modifying poly(epsilon-caprolactone) (PCL) with silk fibroin (SF) in a porous structure. Scanning electronic microscopy revealed that the morphology of the PCL-SF hybrid scaffold was affected by the concentration of the SF solution. Availability of SF on the surface and the conformational transition induced by methanol treatment were proved by attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR), and wettability of the hybrid scaffold was greatly improved. To evaluate scaffold biocompatibility, human fibroblasts were cultured on the hybrid scaffold with the unmodified PCL scaffold as control. An MTT assay indicated that although fewer cells were initially held on the hybrid scaffold after one day of culture, comparable cell numbers were achieved after four days and significantly more cells proliferated on the hybrid after seven days. The cell morphology also indicated that the PCL-SF hybrid scaffold was favorable for cell culture. This study suggests that surface modification with SF would be an effective way to improve the biocompatibility of PCL, facilitating its application in practical tissue engineering.

The inflammatory activity of ulcerative colitis plays an important role in the medical treatment. However, accurate and real-time monitoring of the colitis activity with noninvasive bioimaging method is still challenging, especially in distinguishing between chronic and acute colitis. As a good receptor, the oligopeptide transporter (PepT1) is overexpressed in the colonic epithelial cells of chronic ulcerative colitis, which can deliver tripeptide KPV (Lys-Pro-Val, the C-terminal sequence of α-MSH) into cytosol in the intestine. Herein, we report a PepT1 peptide receptor-targeted fluorescent probe, dicyanomethylene-4H-pyran (DCM)-KPV, with the strategy of conjugating the KPV into the DCM chromophore. The diagnostic fluorescent probe bestows a specific receptor-targeted interaction with PepT1 through the KPV moiety, possessing several beneficial characteristics, such as efficient long emission, low photobleaching, negligible cytotoxicity, and high cytocompatibility in living cells. We build the overexpressed PepT1 on the cytomembrane of ulcerative colitis model Caco-2 cell as the efficient receptor to accumulate the targeted tripeptide KPV in the cytoplasm and nucleus. With the co-localization of DCM-KPV and the DNA-specific fluorophore, DAPI, the specifically long emission from chromophore DCM and efficient receptor-targeted peptide KPV, the fluorescent probe of DCM-KPV makes a breakthrough to the direct noninvasive observation of the accumulation in colon inflammation regions via intestinal mucosa, even successfully distinguishing the chronic, acute ulcerative colitis and normal groups. Compared with the traditional unenhanced magnetic resonance imaging and hematoxylin and eosin (H&E) staining, we make full use of exploiting the specific target-receptor interaction between the tripeptide unit, KPV, and the oligopeptide transporter, PepT1, for sensing selectivity. The desirable diagnostic ability of DCM-KPV can guarantee the real-time tracking and visualization of the role of intracellular KPV on ulcerative colitis, which provides an alternative to replace the time-consuming and tissue sampling-invasive H&E staining diagnosis.

Mast cells have been demonstrated to accumulate around and within solid tumors of numerous types, and express a number of pro-angiogenic compounds, including tryptase. They may serve an early role in angiogenesis within developing tumors. In the present study, the role and mechanism of tryptase in the activation of endothelial progenitor cells (EPCs) in breast cancer angiogenesis were evaluated. Human umbilical cord blood EPCs were isolated and cultured. MB-MDA-231 breast cancer cells were then pretreated with tryptase, and the conditioned medium was collected. The effects of tryptase on the migratory and angiogenesis abilities of EPCs were determined using wound-healing and tube formation assays, respectively. The effect of tryptase on the proliferation of EPCs was detected using a Cell Counting Kit-8 assay. Alterations in proteinase activated receptor (PAR)-2, phosphorylated (p)-protein kinase B (AKT), p-extracellular signal-regulated kinase (p-ERK) and vascular endothelial growth factor receptor (VEGFR)-2 expression were analyzed, in tryptase or conditioned medium-treated EPCs, by western blot analysis and reverse transcription-quantitative polymerase chain reaction. It was confirmed that the EPCs expressed PAR-2; and that tryptase treatment promoted the migration and tube formation of EPCs. Treatment with a PAR-2 agonist had a similar effect to tryptase, whereas treatment with a tryptase inhibitor, APC366, or a PAR-2 inhibitor, SAM 11, inhibited the effect of tryptase treatment. Tryptase and PAR-2 agonists did not affect the rate of EPC proliferation. MB-MDA-231 cells also expressed PAR-2. Treatment with tryptase or conditioned medium increased the expression of PAR-2, p-AKT, p-ERK and VEGFR-2 in EPCs. In conclusion, tryptase activated EPCs via PAR-2-mediated AKT and ERK signaling pathway activation, thereby enhancing angiogenesis in breast cancer.