Simvastatin-loaded lyophilized wafers as a potential dressing for chronic wounds

Wafers are an established drug delivery system for application to suppurating wounds. They can absorb wound exudates and are converted into a gel, offering a moist environment that is vital for wound healing. Simvastatin-loaded lyophilized wafers were developed using sodium carboxymethyl cellulose (CMC) and methyl cellulose (MC) and evaluated for their potential in the management of chronic wounds. Simvastatin (SIM) was chosen as the model drug since it is known to accelerate wound healing by promoting angiogenesis and lymphangiogenesis. Pre-formulation studies were carried out with CMC, MC, and a mixture of CMC and MC. Wafers obtained from aqueous gels of 3% CMC and blend of CMC-MC in the % weight ratio of 2:1 and 1.5:1.5 were selected for further analysis. The formulated wafers were characterized by microscopic examination, texture analysis, hydration test, rheological studies, FTIR spectroscopy, water vapor transmission and drug release test. Among the selected formulations, simvastatin-loaded CMC-MC (2:1) wafers exhibited the most desired characteristics for wound dressing application, such as good flexibility, hardness, sponginess, and viscosity. It showed a sustained drug release, which is desirable in wound healing, and was more appropriate for suppurating wounds. In conclusion, simvastatin-loaded CMC-MC (2:1) wafers showing potential for wound dressing applications were successfully developed.     

Microstructural and electrical properties of sintered tungsten trioxide

Tungsten trioxide sintered wafers were prepared from WO₃ powder obtained when ammonium paratungstate is decomposed in air at moderate temperature. Two wafer series of five samples were sintered under the same conditions in the temperature range 600–1000 °C. One of these wafers series was submitted to a subsequent annealing at 700 °C under a hydrogen atmosphere. All samples were characterized at room temperature by X-ray diffraction and electrical measurements. X-ray spectra show that WO₃ ceramic presents a mixture of the triclinic and monoclinic phases before the reduction process. After the reduction process, WO₂ and four hydrogen tungsten bronze phases are present in wafers. Capacitance measurements showed that the samples submitted only to the sintering process changed the dielectric constant with the frequency according to the Debye model. The reduced WO₃ shows a semiconductor behavior, as determined by electrical resistivity measurements.     

Preparation and function of composite asymmetric chitosan/CM-chitosan membrane

A novel composite asymmetric chitosan/CM-chitosan membrane (C-P-C) was prepared, the top-layer was chitosan (CS), the intermediate was PVA, and the substrate was carboxymethyl chitosan (CM-CS). C-P-C membrane had capability in mechanical strength, light transparence, vapor permeability, and wound skin joining. The CS and CM-CS in C-P-C membrane were selected by series independent experiments, respectively. CS (MW 90,000 Da) had the highest antibacterial activity for E.coli. CM-CS had biocompatibility, no cytotoxicity, and had the activity of promoting growth of human skin fibroblast and inhibiting the growth of keloid fibroblast. The normal skin fibroblast can growth on the CM-CS surface of C-P-C, and have no conglomeration in higher cell density, and the keloid fibroblast could not growth on CM-CS surface of C-P-C. The animal experiment demonstrated that wound, covered with the C-P-C membrane, was hemostatic, healing quickly and had histocompatibility. The results indicated that the C-P-C membrane could be used as dressing of skin repair, and had the potential in promoting wound healing and inhibiting the keloid formation.     

In vitro evaluation of freeze-dried bone allografts combined with platelet rich plasma and human bone marrow stromal cells for tissue engineering

Freeze-dried bone allograft (FDBA) might be more effective in combination with platelet rich plasma (PRP) and bone marrow stromal cells (BMSC) in accelerating bone healing. The isolation of BMSC through density gradient (pBMSC) is not extensively applicable in clinical practice, because it increases the risk of infection. Alternatively, BMSC can be concentrated by simple centrifugation (wBMSC) directly in the operating room. However, we do not know if wBMSC act in the same way as pBMSC. BMSC from 10 donors were tested whether, in the presence of a combination of FDBA and autologous PRP, the osteogenic differentiation of the cells concentrated by simple centrifugation (wBMSC + FDBA + PRP) was similar to that of pBMSC. Cell-associated alkaline phosphatase, osterix and fibroblast growth factor-2 were higher in wBMSC + FDBA + PRP. In conclusion, the combination of FDBA and PRP had a favouring effect on the differentiation towards osteoblasts and allowed BMSC concentrated by simple centrifugation to differentiate as fast as BMSC purified by density gradient.     

等离子体源离子注入法制备类金刚石薄膜

用等离子体源注入(PSII)在Si(100)上制备类金刚石膜，放电气体采用CH4，用微波电子回旋共振(ECR)产生等离子体。将-20～-30kV的高压加在衬底上，来提高离子的能量。通过Raman光谱和FT-IR光谱检测了类金刚石膜的化学组成及状态，并对其机械性能和表面形貌进行了检测。结果显示，硅片硬度和摩擦因数得到了改善，用PSII能够制备出性能优良的膜，可以将其应用到微电子器件(MEMS)上去。     

Design and characterization of a chitosan physical gel promoting wound healing in mice

In this study, a sterile and biocompatible chitosan (CHI) gel for wound healing applications was formulated. CHI powder was treated in autoclave (ttCHI) to prepare sterile formulations. The heat treatment modified the CHI molecular weight, as evidenced by GPC analysis, and its physical–chemical features. Differential scanning calorimetry studies indicated that the macromolecules, before and after thermal treatment, differ in the strength of water-polymer interaction leading to different viscoelastic and flow properties. Thermally treated CHI exhibited the following effects: (i) increased the proliferation and migration of human foreskin foetal fibroblasts at 24 h; (ii) accelerated wound healing (measured as area of lesion) at 3 and 10 days in an in vivo model of pressure ulcers. These effects were linked to the increase of the hydroxyproline and haemoglobin content as well as Wnt protein expression. Moreover, we found a reduction of myeloperoxidase activity and TNF-α mRNA expression. These observations suggest the potential of this novel CHI gel in wound healing and other therapeutic applications.     

Development and physico-mechanical characterization of carrageenan and poloxamer-based lyophilized matrix as a potential buccal drug delivery system

Context and objectives: The buccal mucosa presents a unique surface for non-invasive drug delivery and also avoids first-pass metabolism. The objective of this study was the formulation development of polymeric mucoadhesive lyophilized wafers as a matrix for potential buccal drug delivery.

Materials and methods: Differential scanning calorimetry (DSC) was used to develop an optimum freeze-cycle, incorporating an annealing step. The wafers were prepared by lyophilization of gels containing three polymers, κ-carrageenan (CAR 911), poloxamer (P407) and polyethylene glycol 600 (PEG 600). The formulations were characterized using texture analysis (for mechanical and mucoadhesion properties), hydration studies, thermogravimetric analysis (TGA), DSC, X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM).

Results and discussion: DSC showed the eutectic temperature (12.8?°C) of the system where the liquid solution and pure solids both existed at a fixed pressure which helped determine the freeze-annealing cycle at 55?°C for 7?h. Mechanical resistance to compression, hydration and mucoadhesion studies showed that optimized wafers were obtained from aqueous gels containing 2% w/w CAR 911, 4% w/w P407 and 4.4% w/w PEG 600. TGA showed residual water of approximately 1% and SEM showed a porous polymeric network that made ease of hydration possible.

Conclusions: Lyophilized wafers by freeze-drying gels containing 2% w/w CAR 911, 4% w/w P407 and 4.4% w/w PEG 600 with optimum physico-mechanical properties has been achieved.     

Assessment of the cutaneous wound healing efficiency of acidic,neutral and alkaline bacterial cellulose membrane in rat

Recent research was conducted to evaluate the healing efficiency of bacterial cellulose (BC) as a wound dressing in different pHs and its possibility of being a smart wound dressing that can indicate pHs. BC was produced by environmentally isolated bacterial strains. After washing the best achieved BC, it was floated in normal saline with different pHs with phenol red used as a pH indicator. Finally the wound healing effects of the acidic, neutral and alkaline BC membranes were evaluated in rat cutaneous wounds. Results showed that one of the isolates which its partial 16srRNA genome had 95% similarity with Gluconacetobacter intermedius, had the thickest layer. The microscopic and macroscopic evaluations showed that the acidic BC had the best healing activity. Although the color of the films remained unchanged during the experiments because they were transparent and thin, these changes could not be easily seen. This suggests the use of thicker films such as the ones which are cross linked with some materials (e.g., sterile gauze). In conclusion the pH can affect the healing ability of natural BC and acidic pH had the best wound healing efficiency. In future it is better to use the acidic BC instead of natural one for different wound healing purposes.     

碳化硅粒径分布对单晶硅线切割的影响

研究不同粒度分布的碳化硅磨料对线切割硅片表面损伤的影响,利用激光粒度仪和扫描电镜对切割前后碳化硅粒径的变化及切割后硅片的形貌进行表征,通过实际切割过程分析,指出粒度分布不均引起的局部切割堵塞而导致的垂直于切割方向的左右侧滑振动,是导致表面损伤的主要原因。结果表明:当碳化硅的粒度分布窄时,线切割硅片表面损伤层浅,表面粗糙度小。     

Characterization of Arsenic Ultra-Shallow Junctions in Silicon Using Photocarrier Radiometry and Spectroscopic Ellipsometry

Photocarrier radiometry (PCR) and spectroscopic ellipsometry (SE) techniques were employed to measure ultra-shallow junction (USJ) wafers. These USJ wafers were prepared by As⁺ ion implantation at energies of 0.5?keV to 5?keV, at a dose of 1?×?10¹⁵ As⁺/cm² and spike annealing. The experimental data showed that the PCR signal versus implantation energy exhibits a monotonic behavior. The damaged layer of the as-implanted wafer and the recrystallization and activation of the post-annealed wafer were evaluated by SE in the spectral range from 0.27???m to 20???m. PCR and SE were shown to provide non-destructive metrology tools for process monitoring in USJ fabrication.     

Scheduling of wafer test processes in semiconductor manufacturing

This research focuses on solving a common wafer test scheduling problem in semiconductor manufacturing. During wafer testing, a series of test processes are conducted on wafers using computer-controlled test stations at various temperatures. The test processes are conducted in a specified order on a wafer lot, resulting in precedence constraints for the schedule. Furthermore, the assignment of the wafer lots to test stations and the sequence in which they are processed affects the time required to set up the test operations. Thus, the set-up times are sequence dependent. Four heuristics are developed to solve the test scheduling problem with the aim of minimizing the makespan required to test all wafers on a set of test stations. The heuristics generate a sorted list of wafer lots as a dispatching sequence and then schedule the wafer lots on test stations in order of appearance on the list. An experimental analysis and two case studies are presented to validate the proposed solution approaches. In the case studies, the heuristics are applied to actual data from a semiconductor manufacturing facility. For both case studies, the proposed solution approaches decrease the makespan by 23–45% compared with the makespan of the actual schedule executed in the manufacturing facility.     

Human platelet rich plasma plus Persian Gulf coral effects on experimental bone healing in rabbit model: radiological, histological, macroscopical and biomechanical evaluation

Coral is an osteoconductive material used as a bone graft extender and human platelet rich plasma has been used as a source of osteoinductive factor. A combination of human platelet rich plasma and coral is expected to create a composite with both osteoconductive and osteoinductive properties. This study examined the effect of a combination of human platelet rich plasma and coral on osteogenesis in vivo using rabbit model of bone healing. A critical size defect of 10 mm elongation was created in the radial diaphysis of 36 rabbit and either supplied with coral-human PRP, or coral alone or left empty (control group). The platelets in the PRP were about 10.1 fold compared to normal blood. Radiographs of each forelimb was taken postoperatively on 1st day and then at the 2nd, 4th, 6th and 8th weeks post injury to evaluate bone formation, union and remodeling of the defect. The operated radiuses were removed on 56th postoperative day and were grossly and histopathologically evaluated. In addition, biomechanical test was conducted on the operated and normal forearms of the rabbits. This study demonstrated that coral-human PRP (hPRP), could promote bone regeneration in critical size defects with a high regenerative capacity. The results of the present study demonstrated that coral-hPRP could be an attractive alternative for reconstruction of the major diaphyseal defects of the long bones in animal models.     

The effects of processing conditions on the density and microstructure of hot-pressed silicon powder

Silicon powder was hot pressed into polycrystalline wafers 1.5 in ( 3.8 cm) diameter using various processing conditions. The submicrometre powder used was a by-product of the fluidized bed decomposition process of silane (SiH₄) in the production of silicon pellets. The effect of temperature (1250–1300°C), pressure (2000–3000 p.s.i.; 13.18–20.67 N mm^–2) and ambient (argon, hydrogen, vacuum) on the density of the hot-pressed powder was studied. All wafers processed had densities >92% of the theoretical density of silicon as determined by Archimedes' density measurements. Hydrogen was found to increase the densification rate of powdered silicon. The mechanism by which this occurs is believed to be the reduction of the native oxide layer of the powders resulting in increased surface transport. The microstructure of the polycrystalline wafers was examined by scanning electron microscopy, and transmission electron microscopy. The general microstructure of the polycrystalline wafers consisted of micrometre-sized grains with twins, stacking faults, and dislocations within the grains. However, under hot-pressing conditions of 1300 °C, 2000 p.s.i., and a hydrogen ambient, the grains of the wafer were on the order of 1 mm. The silicon wafers contained iron, aluminium, carbon and oxygen impurities as determined by secondary ion mass spectroscopy.     

Hyaluronic acid (HA)-based hydrogels for full-thickness wound repairing and skin regeneration

In this work, two kinds of hyaluronic acid (HA)-based hydrogels were fabricated: one is made from physical freezing-thawing of HA solution (HA1), and the other is from chemical cross-linking of HA and polysaccharide (HA2). They were applied to repair full-thickness skin defects with New Zealand rabbits as the test animals, using powder HA and cotton dress as the references. The wound starts to heal after wounds were disinfected with iodine followed by coating with HA2, HA1, HA and cotton dress (the control), respectively. They were recorded as 4 treatments (groups), HA2, HA1, HA and the control. The healing progress was followed and tested in the duration of 56 days, and the biological repairing mechanism was explored. From the wound area alteration, white blood cell (WBC) measurements and H&E staining, HA2 was the most promising treatment in promoting the wound healing with least serious scar formation. Immunochemistry analyses and real-time PCR tests of the bio-factors involved in the wound healing, vascular endothelial growth factor (VEGF), alpha-smooth muscle actin (α-SMA) and transforming growth factor beta-1 (TGF-β1), exhibited that HA2 enhanced VEGF and α-SMA secretion but reduced TGF-β1 expression at early stage, which alleviated the wound inflammation, improved the skin regeneration and relieved the scar formation.     

Preparation,characterization, and in vivo evaluation of nano formulations of ferulic acid in diabetic wound healing

Diabetes mellitus is most common disorder characterize by hyperglycemia. Chronic hyperglycemia may lead to over production of free radicals thereby results in oxidative stress which impaired healing of wounds. Ferulic acid (FA) has been shown to have antidiabetic and antioxidant properties. The aim of the present study was to develop Ferulic acid nanoparticles and to study its hypoglycemic and wound healing activities. Ferulic acid-poly(lactic-co-glycolic acid) (FA-PLGA) nanoparticles were prepared by nano precipitation method. The prepared FA-PLGA nanoparticles had an average size of 240?nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis showed the prepared FA-PLGA nanoparticles were spherical in shape. Drug encapsulation assay showed that 88.49% FA was encapsulated in PLGA. Carbopol 980 was used to formulate FA-PLGA nanoparticles loaded hydrogel. FA-loaded polymeric nanoparticles dispersion (oral administration) and FA-loaded polymeric nanoparticles based hydrogel (topical administration) treated wounds were found to epithelize faster as compared with diabetic wound control group. The hydroxyproline content increased significantly when compared with diabetic wound control. Therefore, the results indicate that FA significantly promotes wound healing in diabetic rats.     

Biodegradable electrospun nanocomposite fibers based on Poly(2-hydroxy ethyl methacrylate) and bamboo cellulose

Electrospun fibers resemble extracellular matrix and are successfully being used in drug delivery and wound healing. The present study reports the extraction of cellulose from natural fiber such as bamboo which is cost effective. It was then added to Poly(2-hydroxy ethyl methacrylate) (pHEMA) solution and electrospun to obtain pHEMA-bamboo cellulose nanocomposite fibers. The characterization of the prepared bamboo cellulose, pHEMA-bamboo cellulose nanocomposite fibers were carried out using FTIR, XRD, TGA and SEM analysis. The biocompatibility of the prepared nanocomposite fiber were studied by MTT extraction method using Vero cell lines. Similarly the anticancer activity of paclitaxel incorporated nanocomposite fibers were assessed using MCF 7 cancer cell lines. The prepared nanocomposite fibers showed 96% cell viability and the paclitaxel incorporated pHEMA-bamboo cellulose nanocomposite fiber showed 7.4% cancer cell viability in 72 h. This proves the applicability of the prepared polymer matrix composite fiber as a fibrous mesh covering the affected skin area for skin cancers or wound healing.     

Influence of radiation crosslinked carboxymethyl-chitosan/gelatin hydrogel on cutaneous wound healing

A series of carboxymethyl chitosan (CM-chitosan) and gelatin hydrogels were prepared by radiation crosslinking. A pre-clinical study was performed by implantation model and full-thickness cutaneous wound model in Sprague–Dawley rats to preliminarily evaluate the biocompatibility, biodegradability and effects on healing. In the implantation test, as a component of the hydrogels, CM-chitosan showed a positive effect on promoting cell proliferation and neovascularization, while gelatin was efficient to stabilize the structure and prolong the degradation time. To evaluate the function on wound healing, the hydrogels were applied to the relatively large full-thickness cutaneous wounds (Φ3.0 cm). Compared with the control groups, the hydrogel group showed significantly higher percentage of wound closure on days 9, 12 and 15 postoperatively, which was consistent with the significantly thicker granulation tissue on days 3 and 6. All results apparently revealed that the radiation crosslinked CM-chitosan/Gelatin hydrogels could induce granulation tissue formation and accelerate the wound healing.     

壳聚糖复合不对称膜的制备及生物组织相容性研究

用分步流延干燥法制备了一种由壳聚糖（CS）、聚乙烯醇（PVA）、羧甲基壳聚糖（CM-CS）构成的新型人工皮肤医用材料——壳聚糖复合不对称膜（C-P-C膜），其上层为CS层，中间为PVA层，下层为CM-CS层。研究结果表明，可通过调节CS、PVA、CM-CS的加入量来控制复合不对称膜各层的厚度和膜的水蒸气通透性，C-P-C膜具有良好的透光性和吸水率。生物相容性实验发现，C-P-C膜是无毒材料，不会引起创伤感染，随着植入C-P-C膜时间的延长，组织炎症反应明显减轻，6周时，炎症浸润程度低于手术缝合线。C-P-C膜能够明显地促进创面愈合，能有效地密封出血创面且具有显著的止血作用。     

A three-dimensional cell-loading system using autologous plasma loaded into a porous β-tricalcium-phosphate block promotes bone formation at extraskeletal sites in rats

The effects of platelet-rich plasma (PRP) and platelet-poor plasma (PPP) on bone marrow stromal cells (MSCs) with respect to proliferation, osteogenic differentiation, and bone formation capability were investigated.MSCs derived from rats were cultured in medium containing mixtures of PRP and PPP. Fibrinogen was eliminated prior to the experiment. The DNA content and alkaline phosphatase (ALP) activity were measured. PRP stimulated cell proliferation and inhibited osteoblastic differentiation. To examine the effects of fibrin in plasma, MSCs were cultured in PRP or PPP fibrin gels formed both on a cell culture insert installed in a culture well and on the bottom surface of the same culture well. The ALP activities of the MSCs in both of the gels were higher than those on the surface of the culture wells. The MSCs cultured on the PPP gel showed the highest ALP activity. The effects of PRP and PPP used as scaffolds for bone formation were also investigated. MSCs were suspended in PRP or PPP, introduced into porous β-tricalcium phosphate blocks, and then implanted into subcutaneous sites. Subsequently, bone formation was quantified. Further in vivo studies found that implants prepared using PPP had a greater osteoinductive capability than implants prepared with PRP.     

Studies of photoconductance decay method for characterization of near-surface electrical properties of semiconductors

The Photoconductance Decay (PCD) method in a standard version allows determination of the bulk properties of semiconductors but is not suitable for evaluation of the surface and near-surface region of the wafer during processing. This experiment is concerned with PCD measurements devised specifically for the purpose of electrical probing using temporary contacts of the near-surface (ns-PCD) region of semiconductor substrates, including thin films. The method is tested through the measurements of the single-crystal, indirect bandgap elemental semiconductor wafers (Si and Ge), as well as selected direct bandgap compound semiconductor wafers (GaAs and InP). In the former case, surface properties of the material tested are altered in a controlled fashion and the PCD response to the surface alteration, in terms of the minority carrier lifetime, is measured. In the case of all substrates studied, a direct correlation between carrier lifetime measured using PCD and the condition of the wafer surface was observed. Furthermore, the ns-PCD method was proven very effective in measuring minority carrier lifetime at the semiconductor-dielectric interface without having to form MOS test structures. The results obtained suggest that the modified PCD method employing temporary contacts to the measured surface can be used to monitor the condition of semiconductor surfaces during device processing.