Biological evaluation of intervertebral disc cells in different formulations of gellan gum‐based hydrogels

Gellan gum (GG)‐based hydrogels are advantageous in tissue engineering not only due to their ability to retain large quantities of water and provide a similar environment to that of natural extracellular matrix (ECM), but also because they can gelify in situ in seconds. Their mechanical properties can be fine‐tuned to mimic natural tissues such as the nucleus pulposus (NP). This study produced different formulations of GG hydrogels by mixing varying amounts of methacrylated (GG‐MA) and high‐acyl gellan gums (HA‐GG) for applications as acellular and cellular NP substitutes. The hydrogels were physicochemically characterized by dynamic mechanical analysis. Degradation and swelling abilities were assessed by soaking in a phosphate buffered saline solution for up to 170 h. Results showed that as HA‐GG content increased, the modulus of the hydrogels decreased. Moreover, increases in HA‐GG content induced greater weight loss in the GG‐MA/HA‐GG formulation compared to GG‐MA hydrogel. Potential cytotoxicity of the hydrogel was assessed by culturing rabbit NP cells up to 7 days. An MTS assay was performed by seeding rabbit NP cells onto the surface of 3D hydrogel disc formulations. Viability of rabbit NP cells encapsulated within the different hydrogel formulations was also evaluated by Calcein‐AM and ATP assays. Results showed that tunable GG‐MA/HA‐GG hydrogels were non‐cytotoxic and supported viability of rabbit NP cells. Copyright © 2012 John Wiley & Sons, Ltd.     

Horseradish peroxidase‐catalysed in situ‐forming hydrogels for tissue‐engineering applications

In situ‐forming hydrogels are an attractive class of implantable biomaterials that are used for biomedical applications. These injectable hydrogels are versatile and provide a convenient platform for delivering cells and drugs via minimally invasive surgery. Although several crosslinking methods for preparing in situ forming hydrogels have been developed over the past two decades, most hydrogels are not sufficiently versatile for use in a wide variety of tissue‐engineering applications. In recent years, enzyme‐catalysed crosslinking approaches have been emerged as a new approach for developing in situ‐forming hydrogels. In particular, the horseradish peroxidase (HRP)‐catalysed crosslinking approach has received increasing interest, due to its highly improved and tunable capacity to obtain hydrogels with desirable properties. The HRP‐catalysed crosslinking reaction immediately occurs upon mixing phenol‐rich polymers with HRP and hydrogen peroxide (H₂O₂) in aqueous media. Based on this unique gel‐forming feature, recent studies have shown that various properties of formed hydrogels, such as gelation time, stiffness and degradation rate, can be easily manipulated by varying the concentrations of HRP and H₂O₂. In this review, we outline the versatile properties of HRP‐catalysed in situ‐forming hydrogels, with a brief introduction to the crosslinking mechanisms involved. In addition, the recent biomedical applications of HRP‐catalysed in situ‐forming hydrogels for tissue regeneration are described. Copyright © 2014 John Wiley & Sons, Ltd.     

Incorporation of magnesium ions into photo‐crosslinked alginate hydrogel enhanced cell adhesion ability

Photo‐crosslinked alginate hydrogel attracts wide interest in tissue engineering because of its excellent controllability and stability. However, its highly hydrophilic property makes cell adhesion difficult. Plenty of studies have confirmed that magnesium ions (Mg²⁺) can efficiently improve the attachment of osteoblasts. In this study, for the first time, we fabricated a durable, crosslinked, alginate hydrogel with a dual‐crosslinking network. Photo‐crosslinked alginate hydrogel was chosen as the basic backbone, and various amounts of Mg²⁺ were incorporated into the hydrogel through ionic crosslinking. The results showed that the physicochemical properties of the hydrogels, including surface structure, composition, swelling ratio, ion release and elastic modulus, could be well tuned by controlling the amount of Mg²⁺ incorporated. In addition, a certain amount of Mg²⁺ significantly improved the attachment and spread of osteoblasts on the hydrogels. These characteristics make Mg²⁺‐incorporated photo‐crosslinked alginate hydrogel a promising scaffold for bone tissue engineering. Copyright © 2015 John Wiley & Sons, Ltd.     

玻璃体切割硅油填充术后眼压变化的分析及护理

目的 探讨玻璃体切割联合硅油填充术后患者眼压变化及护理措施.方法 对52例(52眼)玻璃体切割硅油填塞术后患者的临床资料进行回顾性分析,总结护理措施.结果 24例(46.2％)患者出现高眼压,其中19例发生在术后2周内(79.2％).高眼压组与眼压正常组性别、年龄,病程、屈光度及硅油填充量比较早发现,早处理差异均无统计学意义(P＞0.05).结论 玻璃体切割联合硅油填充术后早期高眼压临床较常见,应加强患者的病情观察,防止术后并发症.     

PEG hydrogel degradation and the role of the surrounding tissue environment

Poly(ethylene glycol) (PEG)‐based hydrogels are extensively used in a variety of biomedical applications, due to ease of synthesis and tissue‐like properties. Recently there have been varied reports regarding PEG hydrogel's degradation kinetics and in vivo host response. In particular, these studies suggest that the surrounding tissue environment could play a critical role in defining the inflammatory response and degradation kinetics of PEG implants. In the present study we demonstrated a potential mechanism of PEG hydrogel degradation, and in addition we show potential evidence of the role of the surrounding tissue environment on producing variable inflammatory responses. Copyright © 2013 John Wiley & Sons, Ltd.     

A randomised controlled trial of the effectiveness of soft silicone multi‐layered foam dressings in the prevention of sacral and heel pressure ulcers in trauma and critically ill patients: the border trial

The prevention of hospital acquired pressure ulcers in critically ill patients remains a significant clinical challenge. The aim of this trial was to investigate the effectiveness of multi‐layered soft silicone foam dressings in preventing intensive care unit (ICU) pressure ulcers when applied in the emergency department to 440 trauma and critically ill patients. Intervention group patients (n = 219) had Mepilex^® Border Sacrum and Mepilex^® Heel dressings applied in the emergency department and maintained throughout their ICU stay. Results revealed that there were significantly fewer patients with pressure ulcers in the intervention group compared to the control group (5 versus 20, P = 0·001). This represented a 10% difference in incidence between the groups (3·1% versus 13·1%) and a number needed to treat of ten patients to prevent one pressure ulcer. Overall there were fewer sacral (2 versus 8, P = 0·05) and heel pressure ulcers (5 versus 19, P = 0·002) and pressure injuries overall (7 versus 27, P = 0·002) in interventions than in controls. The time to injury survival analysis indicated that intervention group patients had a hazard ratio of 0·19 (P = 0·002) compared to control group patients. We conclude that multi‐layered soft silicone foam dressings are effective in preventing pressure ulcers in critically ill patients when applied in the emergency department prior to ICU transfer.     

硅胶啫喱垫在俯卧位手术中的应用

目的:观察硅胶啫喱垫在俯卧位手术中的应用效果。方法:通过使用传统弓形脊柱手术托架摆放俯卧位与使用啫喱垫摆放俯卧位的比较,总结两种摆放手术体位的临床效果。结果:采用硅胶啫喱体位垫可有效缩短患者摆放体位时间,减少因手术体位引发的并发症。结论:采用硅胶啫喱垫摆放俯卧位不但操作简便,而且可以达到保护患者安全的目的,值得临床推广应用。     

Macular Perfusion Changes and Ganglion Cell Complex Loss in Patients with Silicone Oil-related Visual Loss

Objective The aim of this study was to investigate macular perfusion changes and ganglion cell complex(GCC) loss in patients with unexplained visual loss following vitrectomy and silicone oil(SO)tamponade, and to evaluate the correlation between retinal blood flow and GCC loss using optical coherence tomography angiography(OCTA) and optical coherence tomography(OCT).Methods This retrospective study included seven eyes(seven patients) with unexpected visual loss after vitrectomy and SO tamponade. OCTA was used to evaluate the alterations in retinal vessel density(VD) in the superficial capillary plexus(SCP), deep capillary plexus(DCP), and radial peripapillary capillary plexus(RPCP). OCT was used to measure the thickness of GCC and retinal nerve fiber layer(RNFL).Medical records of patients were reviewed.Results Quantitative analysis of OCTA images revealed a significant reduction in SCP VD in the affected eyes compared with the controls(all sections P 0.05). No difference was found in GCC thickness, but FLV(focal loss volume) and GLV(global loss volume) were significantly higher in the affected eyes(both P 0.001). SCP VD was inversely correlated with FLV and GLV.Conclusions Silicone oil-related severe visual loss was associated with superficial retinal microvasculature damage and ganglion cell apoptosis.     

A Self-Healing Hierarchical Fiber Hydrogel That Mimics ECM Structure

Although there have been many studies on using hydrogels as substitutes for natural extracellular matrices (ECMs), hydrogels that mimic the structure and properties of ECM remain a contentious topic in current research. Herein, a hierarchical biomimetic fiber hydrogel was prepared using a simple strategy, with a structure highly similar to that of the ECM. Cell viability experiments showed that the hydrogel not only has good biocompatibility but also promotes cell proliferation and growth. It was also observed that cells adhere to the fibers in the hydrogel, mimicking the state of cells in the ECM. Lastly, through a rat skin wound repair experiment, we demonstrated that this hydrogel has a good effect on promoting rat skin healing. Its high structural similarity to the ECM and good biocompatibility make this hydrogel a good candidate for prospective applications in the field of tissue engineering.     

PEG-g-chitosan thermosensitive hydrogel for implant drug delivery: cytotoxicity,in vivo degradation and drug release

Thermosensitive hydrogels based on chitosan are of great interests for injectable implant drug delivery. The poly(ethylene glycol)-grafted-chitosan (PEG-g-CS) hydrogel was reported as a potential thermosensitive system. The objective of the present study is to evaluate the cytotoxicity, in vivo degradation and drug release of PEG-g-CS hydrogel. Cytotoxicity was evaluated using L929 murine fibrosarcoma cell line. Degradation and drug release in vivo were investigated by subcutaneous injection of the hydrogel into Sprague-Dawley rats. PEG-g-CS polymer exhibits no significant cytotoxicity when its concentration is less than 3 mg mL^?1. After being implanted, PEG-g-CS hydrogel maintains its integrity for two weeks and collapses, merging into the tissue, in the third week. It causes moderate inflammatory response but no fibrous encapsulation around the hydrogel is found. The hydrogel presents a three-week sustained release of cyclosporine A with no significant burst release in vitro and produces the effective drug concentration in blood for more than five weeks in vivo, performing almost the same bioavailability to chitosan/glycerophosphate hydrogel. Further modifications of PEG-g-CS hydrogel might be necessary to modulate the degradation and to mitigate the fluctuations in blood drug concentration.