Effect of a Gelatin Hydrogel Incorporating Epiregulin on Human Keratinocyte Growth

Abstract

Ionic hydrogels are biocompatible interesting candidates for tissue-engineering applications, such as the creation of artificial skin, as they can also be used, along with growth factors and cells grown in vitro, for developing bioengineered tissues to be implanted. Among the growth factors that can be used to induce keratinocytes growth in vitro, epiregulin, a broad-specificity epidermal growth factor (EGF) family member, has been shown to be more effective than EGF and transforming growth factor-alpha (TGF-α) in promoting re-epithelization in vitro. To produce a drug-delivery hydrogel for epiregulin, bovine gelatin was cross-linked with poly(glutamic acid) (PLG) in the presence of epiregulin (5–50 ng/ml). Spontaneously immortalized human keratinocytes (HaCaT) were seeded on unloaded and epiregulin-loaded hydrogels and cell adhesion was evaluated after 6 h. Moreover, cell proliferation and stratification, cytokeratins (K5, K10), differentiation markers (filaggrin and transglutaminase-1 (TG-1)) and matrix metalloproteinases (MMP-2, MMP-9 and MMP-28) expression were evaluated after 7 days. The presence of epiregulin induced an increase in cell proliferation, stratification and K5 expression along with MMP-9 and MMP-28 expression, while all differentiation markers expression (K10, filaggrin, TG-1) was decreased. These data indicated that a simple hydrogel loaded with epiregulin could be an effective tool for skin tissue engineering.     

Preparation,pharmacokinetics and pharmacodynamics of ophthalmic thermosensitive in situ hydrogel of betaxolol hydrochloride

Conventional ophthalmic formulations often eliminate rapidly after administration and cannot provide and maintain an adequate concentration of the drug in the precorneal area. To solve those problems, a thermosensitive in situ gelling and mucoadhesive ophthalmic drug delivery system was prepared and evaluated, the system was composed of poloxamer analogs and polycarbophil (PCP) and betaxolol hydrochloride (BH) was selected as model drug. The concentrations of poloxamer 407 (P407) (22% (w/v)) and poloxamer 188 (P188) (3.5% (w/v)) were identified through central composite design-response surface methodology (CCD-RSM). The BH in situ hydrogel (BH-HG) was liquid solution at low temperature and turned to semisolid at eye temperature. BH-HG showed good stability and biocompatibility, which fulfilled the requirements of ocular application. In vitro studies indicated that addition of PCP enhanced the viscosity of BH-HG and the release results of BH from BH-HG demonstrated a sustained release behavior of BH because of the gel dissolution. In vivo pharmacokinetics and pharmacodynamics studies indicated that the BH-HG formulation resulted in an improved bioavailability and a significantly lower intraocular pressure (IOP). The results suggested BH-HG could be potentially used as an in situ gelling system for ophthalmic delivery to enhance the bioavailability and efficacy.     

Sodium oleate induced rapid gelation of silk fibroin

Silk fibroin has acquired increasing interest in the last years for application in medicine and namely in tissue engineering. Several methods have been developed to process fibroin and for the fabrication of nets, sponges, films and gels. This paper deals with the fabrication and characterization of fibroin hydrogels obtained by using sodium oleate as gelation agent. Gels have been prepared by mixing Silk fibroin (SF) and Sodium oleate (SO) water solutions in different concentrations, and a quite wide frame of compositions have been explored. Rheological tests have been performed to determine the gelation times, scanning electron microscopies have been made to evaluate morphologies, FTIR analysis has been done to determine the conformation of the starting materials and of the resulting gels, water content has been measured and cytotoxicity tests have been performed to validate the potential biomedical use of the hydrogels. Depending on the SF and SO different gelation times have been obtained thanks to the formation of intermolecular bonds between the fibroin chains. The obtained fastest gelation of about 80 s could make this specific formulation compatible with in situ gelation. By changing composition, gels with different morphologies, rheological properties and water contents have been prepared.     

Polarization second harmonic generation by image correlation spectroscopy on collagen type I hydrogels

Successful engineering of biomimetic tissue relies on an accurate quantification of the mechanical properties of the selected scaffold. To improve this quantification, typical bulk rheological measurements are often complemented with microscopic techniques, including label-free second harmonic generation (SHG) imaging. Image correlation spectroscopy (ICS) has been applied to obtain quantitative information from SHG images of fibrous scaffolds. However, the typical polarization SHG (P-SHG) effect, which partly defines the shape of the autocorrelation function (ACF), has never been taken into account. Here we propose a new and flexible model to reliably apply ICS to P-SHG images of fibrous structures. By starting from a limited number of straightforward assumptions and by taking into account the P-SHG effect, we were able to cope with the typically observed ACF particularities. Using simulated datasets, the resulting model was thoroughly evaluated and compared with models previously described in the literature. We showed that our new model has no restrictions concerning the fibre length for the density retrieval. For certain length ranges, the model can additionally be used to obtain the average fibre length and the P-SHG related non-zero susceptibility tensor element ratios. From experimental data on collagen type I hydrogels, values of SHG tensor element ratios and fibre thickness were determined which match values reported in the literature, thereby underpinning the validity and applicability of our new model.     

泪道探通术联合硅胶管植入术治疗鼻泪管阻塞的护理研究

目的探讨泪道探通术联合硅胶管植入术的临床护理对提高鼻泪管阻塞患者的治愈率,缓解患者生理、心理上痛苦的效果。方法筛选2011年10月-2013年10月就诊于武警后勤学院附属医院眼科的50例(50眼)鼻泪管阻塞患者,通过泪道探通术联合硅胶管植入术进行治疗,并对其实施围术期护理和出院指导,观察其预后疗效。结果治愈42眼,好转6眼,无效2眼,有效率:治愈+好转=96%。结论通实施对泪道探通术联合硅胶管植入术的围术期护理和出院指导,可提高鼻泪管阻塞患者的治疗成功率,从而使患者的疾病得到改善,生活质量得到提高。     

Assessing glucose and oxygen diffusion in hydrogels for the rational design of 3D stem cell scaffolds in regenerative medicine

Hydrogels are attractive biomaterials for replicating cellular microenvironments, but attention needs to be given to hydrogels diffusion properties. A large body of literature shows the promise of hydrogels as 3D culture models, cell expansion systems, cell delivery vehicles, and tissue constructs. Surprisingly, literature seems to have overlooked the important effects of nutrient diffusion on the viability of hydrogel‐encapsulated cells. In this paper, we present the methods and results of an investigation into glucose and oxygen diffusion into a silated‐hydroxypropylmethylcellulose (Si‐HPMC) hydrogel. Using both an implantable glucose sensor and implantable oxygen sensor, we continuously monitored core glucose concentration and oxygen concentration at the centre of hydrogels. We demonstrated that we could tune molecular transport in Si‐HPMC hydrogel by changing the polymer concentration. Specifically, the oxygen diffusion coefficient was found to significantly decrease from 3.4 × 10^?10 to 2.4 × 10^?10 m² s^?1 as the polymer concentration increased from 1% to 4% (w/v). Moreover, it was revealed during in vitro culture of cellularized hydrogels that oxygen depletion occurred before glucose depletion, suggesting oxygen diffusion is the major limiting factor for cell survival. Insight was also gained into the mechanism of action by which oxygen and glucose diffuse. Indeed, a direct correlation was found between the average polymer crosslinking node size and glucose parameters, and this correlation was not observed for oxygen. Overall, these experiments provide useful insights for the analysis of nutrient transport and gas exchange in hydrogels and for the development of future cellular microenvironments based on Si‐HPMC or similar polysaccharide hydrogels.     

Release of Ciprofloxacin-HCl and Dexamethasone Phosphate by Hyaluronic Acid Containing Silicone Polymers

The purpose of this study was to determine the effect of the covalent incorporation of hyaluronic acid (HA) into conventional hydrogel and hydrogels containing silicone as models for contact lens materials on the uptake and release of the fluoroquinolone antibiotic ciprofloxacin and the anti-inflammatory steroid dexamethasone phosphate. A 3 mg/mL ciprofloxacin solution (0.3% w/v) and a 1 mg/mL dexamethasone phosphate solution (0.1%) was prepared in borate buffered saline. Three hydrogel material samples (pHEMA; pHEMA TRIS; DMAA TRIS) were prepared with and without the covalent incorporation of HA of molecular weight (MW) 35 or 132 kDa. Hydrogel discs were punched from a sheet of material with a uniform diameter of 5 mm. Uptake kinetics were evaluated at room temperature by soaking the discs for 24 h. Release kinetics were evaluated by placing the drug-loaded discs in saline at 34 °C in a shaking water bath. At various time points over 6–7 days, aliquots of the release medium were assayed for drug amounts. The majority of the materials tested released sufficient drug to be clinically relevant in an ophthalmic application, reaching desired concentrations for antibiotic or anti-inflammatory activity in solution. Overall, the silicone-based hydrogels (pHEMA TRIS and DMAA TRIS), released lower amounts of drug than the conventional pHEMA material (p < 0.001). Materials with HA MW132 released more ciprofloxacin compared to materials with HA MW35 and lenses without HA (p < 0.02). Some HA-based materials were still releasing the drug after 6 days.