Chuan Yang

Genipin-crosslinked casein hydrogels for controlled drug delivery.

Recent advances in hydrogel technology have focused on finding more biocompatible, non-toxic materials intended for pharmaceutical and biomedical applications. In this study, naturally occurring genipin was used for the first time to crosslink casein protein in aqueous system for the formation of novel hydrogel materials. For aqueous 8.0 wt% casein solution, its gelation in the presence of genipin was investigated by time sweep rheometric measurements. With the increase of genipin amount from 2.5 to 10.0 mmol/L, the gelation time decreased from 119.8. to 18.5 min when the reaction temperature was kept to be 35 degrees C. With the increase of the reaction temperature from 35 to 50 degrees C, the gelation time decreased from 44.7 to 27.6 min when genipin concentration was kept to be 5.0 mmol/L. The apparent activation energy was determined to be 28.6 kJ/mol according to the Arrhenius equation. Moreover, the mechanical strength of the crosslinked casein hydrogel could be tuned by the amount of genipin. (13)C NMR analyses confirmed the crosslinking reaction between casein and genipin. For the resultant casein hydrogels, their swelling characteristics and in vitro release profiles of bovine serum albumin (BSA) were studied in simulated gastrointestinal tract conditions (pH 1.2 and pH 7.4). At pH 1.2, the swelling ratio of the hydrogel and the release amount of the entrapped BSA were relatively low. However, high amounts of the swelling and BSA release could be observed at pH 7.4. The release behavior could be related to various crosslinking and swelling degrees of the hydrogel networks formed by various amounts of genipin. It is suggested that the genipin-crosslinked casein hydrogel might be a suitable polymeric carrier for protein drug delivery in the intestine.

Star-shaped polymers consisting of a β-cyclodextrin core and poly(amidoamine) dendron arms: binding and release studies with methotrexate and siRNA

To develop multifunctional polymeric carrier for small interfering RNA (siRNA) and drug delivery, novel star-shaped polymers were synthesized by the copper catalyzed azide alkyne cyclization reactions of propargyl focal point poly(amidoamine) dendrons with per-6-azido-β-cyclodextrin, and were characterized by 1H NMR, FTIR and GPC analyses. Their physicochemical properties such as buffering capability, siRNA binding ability and in vitro cytotoxicity as well as their complexation with siRNA in aqueous system were also investigated. Under the optimized conditions, such cationic polymers could exhibit high siRNA transfection efficiency and low cytotoxicity in fibroblast cells. Moreover, their β-cyclodextrin core with internal hydrophobic cavities could be used simultaneously for the entrapment and sustained release of a poorly water-soluble anti-cancer drug (methotrexate).

Perspectives on: Strategies to Fabricate Starch-based Hydrogels with Potential Biomedical Applications

In this review, some strategies to fabricate starch-based hydrogels are summarized and presented. Hydrophilic hydrogels based on native starch, pure starch components and their derivatives are important due to their swellability in water, biocompatibility and biodegradability. For the preparation of chemically cross-linked starch-based hydrogels, one-step and two-step synthesis by free radical polymerization, cross-linking by chemical reaction of complementary groups and radiation-induced polymerization with the help of gamma or electron beams, are used. For the preparation of physically cross-linked starch-based hydrogels, a novel self-assembly method was used. Some advantages and disadvantages of these synthesis approaches are briefly discussed.

The biological behaviors of rat dermal fibroblasts can be inhibited by high levels of MMP9.

Aims. To explore the effects of the high expression of MMP9 on biological behaviors of fibroblasts. Methods. High glucose and hyperhomocysteine were used to induce MMP9 expression in skin fibroblasts. Cell proliferation was detected by flow cytometry and cell viability by CCK-8. ELISA assay was used to detect collagen (hydroxyproline) secretion. Scratch test was employed to evaluate horizontal migration of cells and transwell method to evaluate vertical migration of cells. Results. The mRNA and protein expressions of MMP9 and its protease activity were significantly higher in cells treated with high glucose and hyperhomocysteine than those in control group. At the same time, the S-phase cell ratio, proliferation index, cell viability, collagen (hydroxyproline) secretion, horizontal migration rate, and the number of vertical migration cells decreased in high-glucose and hyperhomocysteine-treated group. Tissue inhibitor of metalloproteinase 1 (TIMP1), which inhibits the activity of MMP9, recovered the above biological behaviors. Conclusions. High expression of MMP9 in skin fibroblasts could be induced by cultureing in high glucose and hyperhomocysteine medium, which inhibited cell biological behaviors. Inhibitions could be reversed by TIMP1. The findings suggested that MMP9 deters the healing of diabetic foot ulcers by inhibiting the biological behaviors of fibroblasts.

A New Class of Starch-Based Hydrogels Incorporating Acrylamide and Vinyl Pyrrolidone: Effects of Reaction Variables on Water Sorption Behavior

A new class of starch-based hydrogels incorporating acrylamide (AM) and vinyl pyrrolidone (VP) were prepared by ceric ammonium nitrate initiated polymerization in the presence of N,N -methylene bisacrylamide (MBA). The swelling and diffusion characteristics in water were studied with respect to the effects of reaction variables such as the type and amount of starch, the amounts of AM and VP, as well as MBA concentration. It was found that these reaction variables affected the swelling ratio of the hydrogels and the kinetics parameters of the water sorption process. The water transport mechanism in the swelling starch-based hydrogels was non-Fickian diffusion.

Cationic star-shaped polymer as an siRNA carrier for reducing MMP-9 expression in skin fibroblast cells and promoting wound healing in diabetic rats.

Background Excessive expression of matrix metalloproteinase-9 (MMP-9) is deleterious to the cutaneous wound-healing process in the context of diabetes. The aim of the present study was to explore whether a cationic star-shaped polymer consisting of β-cyclodextrin (β-CD) core and poly(amidoamine) dendron arms (β-CD-[D3]7) could be used as the gene carrier of small interfering RNA (siRNA) to reduce MMP-9 expression for enhanced diabetic wound healing. Methods The cytotoxicity of β-CD-(D3)7 was investigated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MMT) method in the rat CRL1213 skin fibroblast cell line. The transfection efficiency of β-CD-(D3)7/MMP-9-small interfering RNA (siRNA) complexes was determined by confocal microscopy and flow cytometry. Quantitative real time (RT) polymerase chain reaction was performed to measure the gene expression of MMP-9 after the transfection by β-CD-(D3)7/MMP-9-siRNA complexes. The β-CD-(D3)7/MMP-9-siRNA complexes were injected on the wounds of streptozocin-induced diabetic rats. Wound closure was measured on days 4 and 7 post-wounding. Results β-CD-(D3)7 exhibited low cytotoxicity in fibroblast cells, and easily formed the complexes with MMP-9-siRNA. The β-CD-(D3)7/MMP-9-siRNA complexes were readily taken up by fibroblast cells, resulting in the downregulation of MMP-9 gene expression (P<0.01). Animal experiments revealed that the treatment by β-CD-(D3)7/MMP-9-siRNA complexes enhanced wound closure in diabetic rats on day 7 post-wounding (P<0.05). Conclusion β-CD-(D3)7 may be used as an efficient carrier for the delivery of MMP-9-siRNA to reduce MMP-9 expression in skin fibroblast cells and promote wound healing in diabetic rats.

Transcutaneous oxygen pressure measurement in diabetic foot ulcers: mean values and cut-point for wound healing.

PURPOSE: The purpose of this study was to investigate mean values and cut-point of transcutaneous oxygen pressure (TcPO2) measurement in patients with diabetic foot ulcers. DESIGN: Prospective, descriptive study. SUBJECTS AND SETTING: Sixty-one patients with diabetes mellitus and foot ulcers comprised the sample. The research setting was Sun Yat-sen Memorial Hospital of SunYat-sen University, Guangzhou, China. METHODS: Participants underwent transcutaneous oxygen (TcPO2) measurement at the dorsum of foot. Patients were classified into 3 groups according to clinical outcomes: (1) ulcers healed with intact skin group, (2) ulcer improved, and (3) ulcer failed to improve. TcPO2 was assessed and cut-points for predicting diabetic foot ulcer healing were calculated. RESULTS: Thirty-six patients healed with intact skin, 8 experienced improvement, and 17 showed no improvement. Mean TcPO2 levels were significantly higher (P< .001) in healed ulcers with intact skin (32 ± 10 mmHg) when compared to the improvement group (30 ± 7 mmHg) and the nonhealing group (15 ± 12 mmHg). All patients with TcPO2⩽ 10 mmHg failed to heal or experienced deterioration in their foot ulcers. In contrast, all patients with TcPO2≥ 40 mmHg achieved wound closure. Measurement of TcPO2 in the supine position revealed a cut-point value of 25 mmHg as the best threshold for predicting diabetic foot ulcer healing; the area under the curve using this cut-point was 0.838 (95% confidence interval = 0.700–0.976). The sensitivity, specificity, positive predictive value, and negative predictive value for TxPO2 were 88.6%, 82.4%, 90.7%, and 72.2%, respectively. CONCLUSION: TcPO2≥ 40 mmHg was associated with diabetic foot ulcer healing, but a TcPO2⩽ 10 mmHg was associated with failure of wound healing. We found that a cut-point of 25 mmHg was most predictive of diabetic foot ulcer healing.

Angiotensin II regulates collagen metabolism through modulating tissue inhibitor of metalloproteinase-1 in diabetic skin tissues

We investigated the effect of angiotensin II (Ang II) on matrix metalloproteinase-1 (MMP-1)/tissue inhibitor of metalloproteinase-1 (TIMP-1) balance in regulating collagen metabolism of diabetic skin. Skin tissues from diabetic model were collected, and the primary cultured fibroblasts were treated with Ang II receptor inhibitors before Ang II treatment. The collagen type I (Coll I) and collagen type III (Coll III) were measured by histochemistry. The expressions of transforming growth factor-β (TGF-β), MMP-1, TIMP-1 and propeptides of types I and III procollagens in skin tissues and fibroblasts were quantified using polymerase chain reaction (PCR), Western blot or enzyme-linked immunosorbent assay (ELISA). Collagen dysfunction was documented by changed collagen I/III ratio in streptozotocin (STZ)-injected mice compared with controls. This was accompanied by increased expression of TGF-β, TIMP-1 and propeptides of types I and III procollagens in diabetic skin tissues. In primary cultured fibroblasts, Ang II prompted collagen synthesis accompanied by increases in the expressions of TGF-β, TIMP-1 and types I and III procollagens, and these increases were inhibited by losartan, an Ang II type 1 (AT1) receptor blocker, but not affected by PD123319, an Ang II type 2 (AT2) receptor antagonist. These findings present evidence that Ang-II-mediated changes in the productions of MMP-1 and TIMP-1 occur via AT1 receptors and a TGF-β-dependent mechanism.

Effect of Intensive Nursing Education on the Prevention of Diabetic Foot Ulceration Among Patients with High-Risk Diabetic Foot: A Follow-Up Analysis

The aim of the study was to discuss the effect of intensive nursing education on the prevention of diabetic foot ulceration among patients at high risk for diabetic foot. One hundred eighty-five diabetes patients at high risk for foot diseases were enrolled in this study and provided with intensive nursing education, including individualized education about diabetes mellitus and diabetic foot diseases, instruction in podiatric care (the right way of washing the foot, the care of foot skin, appropriate choice of shoes and socks, intense examinations and records of feet by patients themselves every day, and the assistant management of calluses). Study subjects were followed up for 2 years. Once the foot ulceration developed, the inducing factors of foot ulceration were inquired about, the ulcers were evaluated, and the incidence of foot ulceration was analyzed before and after the intensive nursing education according to self-paired data. Results showed there were highly statistically significant improvements in the intensive treatment group compared with the control group in plasma glucose, blood pressure, and high-density lipoprotein cholesterol levels. More important is that intensive nursing education helps to prevent diabetic foot ulceration and to decrease the rate of amputation among patients at high risk for diabetic foot.

AGE‐induced keratinocyte MMP‐9 expression is linked to TET2‐mediated CpG demethylation

Studies have documented that unusually high expression of matrix metalloproteinase‐9 (MMP‐9) suppresses wound healing during the late stages of diabetic foot ulcers. Recently, it has been reported that the presence of advanced glycation end products‐bovine serum albumin (AGE‐BSA) resulted in a higher expression of MMP‐9 in skin primary keratinocytes. The aim of the present study was to elucidate the molecular machinery that is responsible for the inappropriately high AGE‐BSA–induced expression of MMP‐9. It has been demonstrated that site‐specific DNA demethylation played an important role in MMP‐9 expression in AGE‐BSA–stimulated keratinocytes. Ten–eleven translocation‐2 (TET2) was up‐regulated, whereas the percentage of methylation in the MMP‐9 promoter was reduced. Furthermore, TET2 directly bound to a fragment surrounding the transcriptional start site in the MMP‐9 promoter region, contributing to the regulation of MMP‐9 expression. In addition, evidence indicated that TET2 affected the migration and proliferation in vitro of cultured skin primary keratinocytes. These findings indicated that TET2 directly interacted with the promoter region of MMP‐9 in diabetic tissues and may be a novel master regulator of wound healing.