Concept: Polyvinyl alcohol
We report a novel method for fabrication of three-dimensional (3D) biocompatible micro-fluidic flow chambers in polydimethylsiloxane (PDMS) by 3D-printing water-soluble polyvinyl alcohol (PVA) filaments as master scaffolds. The scaffolds are first embedded in the PDMS and later residue-free dissolved in water leaving an inscription of the scaffolds in the hardened PDMS. We demonstrate the strength of our method using a regular, cheap 3D printer, and evaluate the inscription process and the channels micro-fluidic properties using image analysis and digital holographic microscopy. Furthermore, we provide a protocol that allows for direct printing on coverslips and we show that flow chambers with a channel cross section down to 40 μm × 300 μm can be realized within 60 min. These flow channels are perfectly transparent, biocompatible and can be used for microscopic applications without further treatment. Our proposed protocols facilitate an easy, fast and adaptable production of micro-fluidic channel designs that are cost-effective, do not require specialized training and can be used for a variety of cell and bacterial assays. To help readers reproduce our micro-fluidic devices, we provide: full preparation protocols, 3D-printing CAD files for channel scaffolds and our custom-made molding device, 3D printer build-plate leveling instructions, and G-code.
The aim of this work was to prepare L-DOPA loaded poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles by a modified water-in-oil-in-water (W(1)/O/W(2)) emulsification solvent evaporation method. A central composite design was applied for optimization of the formulation parameters and for studying the effects of three independent variables: PLGA concentration, polyvinyl alcohol (PVA) concentration and organic solvent removal rate on the particle size and the entrapment efficiency (response variables). Second-order models were obtained to adequately describe the influence of the independent variables on the selected responses. The analysis of variance showed that the three independent variables had significant effects (p < 0.05) on the responses. The experimental results were in perfect accordance with the predictions estimated by the models. Using the desirability approach and overlay contour plots, the optimal preparation area can be highlighted. It was found that the optimum values of the responses could be obtained at higher concentration of PLGA (5%, w/v) and PVA (6%, w/v); and faster organic solvent removal rate (700 rpm). The corresponding particle size was 256.2 nm and the entrapment efficiency was 62.19%. FTIR investigation confirmed that the L-DOPA and PLGA polymer maintained its backbone structure in the fabrication of nanoparticles. The scanning electron microscopic images of nanoparticles showed that all particles had spherical shape with porous outer skin. The results suggested that PLGA nanoparticles might represent a promising formulation for brain delivery of L-DOPA. The preparation of L-DOPA loaded PLGA nanoparticles can be optimized by the central composite design.
The objective of this study was to develop a controlled delivery system for PEGylated octreotide using a Poloxamer based in situ gel forming polymer. PEGylated octreotide kept its full biological activity and higher serum half-life compared to the original octreotide. The designed drug delivery system contained low concentration of Poloxamer 407 (P407) (<0.16%) with polyvinyl alcohol (PVA) as a polymeric additive. Rheological measurements of gel vehicle formulations indicated that the in situ gel forming system with optimum sol-gel transition temperature of 28.7°C could be formed using a combination of P407 and PVA at ratio of 15-10% (w/v). The effect of formulation additives such as buffering agents on rheological behavior demonstrated that sodium bicarbonate and lactic acid have opposite effect on sol-gel transition temperature of the system. Using buffering agents, it was possible to shift the sol-gel transition to lower or higher temperatures. The in vitro release profiles of octreotide and PEGylated octreotide from the selected P407/PVA formulations were measured using a membrane-less device. PEGylated octreotide showed slower release rate from the gel system with different release kinetic compared to octreotide. In animal studies, a sustained release rate was achieved with both PEGylated and non-PEGylated octreotide, but longer delivery was observed for PEGylated octreotide. Tissue histopathological studies confirmed the biocompatibility of the delivery system for PEGylated octreotide, supporting the suitability of P407/PVA mixture as an injectable drug delivery system. The total effects of increasing PEGylated peptide half-life and prolonged release from thermoresponsive gel system offer the potential for sustained delivery of PEGylated octreotide.
PURPOSE: To determine if the pattern of retained contrast on immediate postprocedure computed tomography (CT) after particle embolization of hepatic tumors predicts modified Response Evaluation Criteria in Solid Tumors (mRECIST) response. MATERIALS AND METHODS: This study was approved by the Institutional Review Board with a waiver of authorization. One hundred four liver tumors were embolized with spherical embolic agents (Embospheres, Bead Block, LC Bead) and polyvinyl alcohol. Noncontrast CT was performed immediately after embolization to assess contrast retention in the targeted tumors, and treatment response was assessed by mRECIST criteria on follow-up CT (average time 9.0 ± 7.7 weeks after embolization). Tumor contrast retention (TCR) was determined based on change in Hounsfield units (HUs) of the index tumors between the preprocedure and immediate postprocedure scans; vascular contrast retention (VCR) was rated; and defects in contrast retention (DCR) were also documented. The morphology of residual enhancing tumor on follow-up CT was described as partial, circumferential, or total. Association between TCR variables and tumor response were assessed using multivariate logistic regression. RESULTS: Of 104 hepatic tumors, 51 (49 %) tumors had complete response (CR) by mRECIST criteria; 23 (22.1 %) had partial response (PR); 21 (20.2 %) had stable disease (SD); and 9 (8.7 %) had progressive disease (PD). By multivariate analysis, TCR, VCR, and tumor size are independent predictors of CR (p = 0.02, 0.05, and 0.005 respectively). In 75 tumors, DCR was found to be an independent predictor of failure to achieve complete response (p < 0.0001) by imaging criteria. CONCLUSION: TCR, VCR, and DCR on immediate posttreatment CT are independent predictors of CR by mRECIST criteria.
- Chemphyschem : a European journal of chemical physics and physical chemistry
- Published almost 7 years ago
Mechanical properties of glass fiber reinforced composite materials are affected by fiber sizing. A complex film formation, based on a silane film and PVA/PVAc (polyvinyl alcohol/polyvinyl acetate) microspheres on a glass fiber surface is determined at 1) the nanoscale by using atomic force microscopy (AFM), and 2) the macroscale by using the zeta potential. Silane groups strongly bind through the SiOSi bond to the glass surface, which provides the attachment mechanism as a coupling agent. The silane groups form islands, a homogeneous film, as well as empty sites. The average roughness of the silanized surface is 6.5 nm, whereas it is only 0.6 nm for the non-silanized surface. The silane film vertically penetrates in a honeycomb fashion from the glass surface through the deposited PVA/PVAc microspheres to form a hexagonal close pack structure. The silane film not only penetrates, but also deforms the PVA/PVAc microspheres from the spherical shape in a dispersion to a ellipsoidal shape on the surface with average dimensions of 300/600 nm. The surface area value Sa represents an area of PVA/PVAc microspheres that are not affected by the silane penetration. The areas are found to be 0.2, 0.08, and 0.03 μm(2) if the ellipsoid sizes are 320/570, 300/610, and 270/620 nm for silane concentrations of 0, 3.8, and 7.2 μg mL(-1) , respectively. The silane film also moves PVA/PVAc microspheres in the process of complex film formation, from the low silane concentration areas to the complex film area providing enough silane groups to stabilize the structure. The values for the residual silane honeycomb structure heights (Ha ) are 6.5, 7, and 12 nm for silane concentrations of 3.8, 7.2, and 14.3 μg mL(-1) , respectively. The pH-dependent zeta-potential results suggest a specific role of the silane groups with effects on the glass fiber surface and also on the PVA/PVAc microspheres. The non-silanized glass fiber surface and the silane film have similar zeta potentials ranging from -64 to -12 mV at pH’s of 10.5 and 3, respectively. The zeta potentials for the PVA/PVAc microspheres on the glass fiber surface and within the silane film significantly decrease and range from -25 to -5 mV. The shapes of the pH-dependent zeta potentials are different in the cases of silane groups over a pH range from 7 to 4. A triple-layer model is used to fit the non-silanized glass surface and the silane film. The value of the surface-site density for ΓXglass and ΓXsilane , in which X denotes the AlOSi group, differs by a factor of 10(-4) , which suggests an effective coupling of the silane film. A soft-layer model is used to fit the silane-PVA/PVAc complex film, which is approximated as four layers. Such a simplification and compensation of the microsphere shape gives an approximation of the relevant widths of the layers as the follows: 1) the layer of the silane groups makes up 10 % of the total length (27 nm), 2) the layer of the first PVA shell contributes 30 % to the total length (81 nm), 3) the layer of the PVAc core contributes 30 % to the total length (81 nm), and finally 4) the layer of the second PVA shell provides 30 % of the total length (81 nm). The coverage simulation resulted in a value of 0.4, which corresponds with the assumption of low-order coverage, and is supported by the AFM scans. Correlating the results of the AFM scans, and the zeta potentials sheds some light on the formation mechanism of the silane-PVA/PVAc complex film.
The Aspergillus niger NRC1ami pectinase was evaluated according to its hydrolysis efficiency of dry untreated orange peels (UOP), HCl-treated orange peels and NaOH-treated orange peels (HOP and NOP). Pectinase was entrapped in polyvinyl alcohol (PVA) sponge and the optimum pH and temperature of the free and immobilized enzymes were shifted from 4, 40°C to 6, 50°C respectively. The study of pH stability of free and immobilized pectinase showed that the immobilization process protected the enzyme strongly from severe alkaline pHs. The immobilization process improved the enzyme thermal stability to great instant. The unique feature of the immobilization process is its ability to solve the orange juice haze problem completely. Immobilized enzyme was reused 12 times in orange juice clarification with 9% activity loss from the original activity. Maximum reaction rate (V(max)) and Michaelis-Menten constant (K(m)) of the partially purified form were significantly changed after immobilization.
Vinyl laurate (VL), is used in the manufacture of polyvinyl acetate vinyl laurate copolymer a component of gum base for chewing gum production. The potential toxicity of VL to reproduction was examined in a combined repeated dose and reproduction/developmental toxicity screening study (OECD test guideline 422) and a prenatal developmental toxicity screening study (OECD test guideline 414). VL was administered to Wistar rats by gavage at 0 (controls), 50, 250 and 1000 mg/kg bw/d. There were no signs of systemic toxicity in the parental animals of either study. Adverse effects on reproductive performance and fetal development that could be attributed to the VL treatment were not observed. Thus, the highest dose level tested was a NOAEL in these two studies.
Polyvinyl acetate vinyl laurate copolymer (PVAcVL) is a useful component of gum base for chewing gum production. The safety of PVAcVL was examined in a 4-week and a 13-week oral toxicity study in rats. Finely powdered PVAcVL was administred with the diet at levels of 1.25, 2.0 and 5% in the 4-week study and 1.25, 2.5 and 5% in the 13-week study. There were no treatment related effects on mortality, bodyweight gains feed efficiency, ophthalmoscopic findings, hematological and clinical chemical parameters, neurobehavioral observations as well as gross and histopathological changes of standard organs and tissues. The highest dose tested in the 13-week study (3783 and 4396 mg/kg bw/d for males and females, respectively) proved to be a NOAEL.
Percutaneous device closure of atrial septal defect (ASD) is now considered the choice of treatment. Numerous devices with advantages/disadvantages are currently available and under development. Cardia Ultrasept II ASD occluder has a nitinol frame covered with polyvinyl alcohol (PVA) membrane. Here, a well-documented case of early malfunction of PVA membrane detected in the first week of implantation in a 4-year-old male patient, who underwent an uneventful device closure with 20 mm Cardia Ultrasept II ASD Occluder, is presented. One week after implantation left-to-right shunt through the device was detected and the explantation of device revealed PVA membrane with multiple perforations. © 2015 Wiley Periodicals, Inc.
In this study, a central composite rotatable design based on response surface methodology (RSM) was employed to design and formulate an appropriate paeonol microparticle formulation. Five levels of a three-factor, rotatable, central composite design were used to evaluate the critical formulation variables. The optimum conditions for preparing paeonol-loaded microparticles were predicted to be: polyvinyl alcohol (PVA) content (2.84%), the ratio of drug to polymer (6.88) and the stirring rate (1007.59 rpm). The optimized responses for production yield and loading efficiency were found to be 68.86% and 55.90%, respectively, and the particle size were 23.27 ± 0.76 µm and the sorting coefficient (σ) was 0.732. Furthermore, in vitro release study suggested that microparticle could be a suitable delivery system in treating skin disease for its sustained release of drug. In conclusion, RSM can be successfully used to optimize the effect of formulation variables.