Venina dos Santos

Evaluation of the solubility of the HPMC: PVA blends in biological fluids in vitro

Received: September 22, 2010; Revised: April 28, 2011Polymers are often used to coat tablets for controlled drug release. The purpose of this study is to evaluate the solubility of the HPMC and PVA blend compared to isolated polymers in solutions with a pH of biological fluids (6 and 1.2) and the dissolution of capsules obtained using theophylline granules produced with the HPMC/PVA 25/75 blend as a matrix and as coating. HPMC is completely solubilized in the medium that simulates the pH of the stomach and intestine, and PVA is the polymer that allows controlling the solubility of the blend in the medium, with a differents pH. The dissolution time was monitored by UV absorbance with maximum theophylline at 269 nm. The theophylline was released immediately in the granules, and in the capsules 78.4% after 30 minutes and 97.4%, after 120 minutes. Thus, PVA can potentially control the drug solubilization, contributing to obtaining modified release systems.

Characterization of Polyamide 66 membranes prepared by phase inversion using formic acid and hydrochloric acid such as solvents

The membranes properties prepared from water/formic acid (FA)/ polyamide 66 (PA66) and water/hydrochloric acid (HCl)/polyamide 66 (PA 66) systems has been studied. The different solvents interact distinctly with the polymer, affecting the membrane morphology. The asymmetric structure of the membranes showed a dense top layer and a porous sublayer. The membranes M-HCl prepared from HCl/PA 66 system showed a larger dense layer (around 23 μm) in compared to those prepared from FA/PA 66 system (M-FA) (around 10 μm). The membrane morphology was a determinant factor in results of water absorption, porosity and pure water flux. The lower thickness of dense layer in M-FA membranes resulted in a higher water absorption and, consequently, porosity, approximately 50%, compared with M-HCl membranes, approximately 15%. The same trend was observed to permeate flux, the lower thickness of dense layer higher pure water flux.

Preparation and Characterization of PA66/Alumina Composite Membrane

In this study, polymer/ceramic composite membranes were prepared and characterized. The polymer used was polyamide 66 (PA66) deposited by dip coating on the inner surface of α-alumina-based (Al2O3) microporous tube. A coating on the ceramic support surface and the formation of the selective layer was analyzed by scanning electron microscopy (SEM) in membranes with one (PA-1) and two layers (PA-2). The results of mercury porosimetry showed that the deposition of the polyamide layers decreases the average pore size. The PA-1 presented an average pore size of 0.35 μm, while the PA-2 presented two peaks of 0.18 and 0.56 μm. Both showed a superior performance than the ceramic support (pore diameter of 0.65 μm). Although, the permeate flux was higher with an impregnation membrane, the number of layers (one or two) just introduced a slight difference in pore statistical analysis. The order of rejection coefficient values for protein molecules is BSA > egg albumin > trypsin. The permeation tests showed that the composite membrane can be applied in ultrafiltration processes with MWCO of 69 kDa.

Characterization of Mullite Ceramic Membranes and their Application in the Removal Escherichia Coli

This paper aims the morphological and structural characterization of ceramic membranes of mullite and their application in the removal of Escherichia coli. A complex irregular structure presented by the pores of the membrane was verified by scanning electron microscopy (SEM). The average pore size and distribution were determined by mercury intrusion porosimetry. The average pore size of the material presented was 0,39 µm. Microfiltration tests resulted in a protein retention of 46, 76 and 89% for trypsin (TR), egg albumin (EA) and bovine serum albumin (BSA), proving the efficiency of the membrane microfiltration tests for molecular weight of 69 kDa. The application of the membranes on the retention of gram-negative bacterium E. coliresulted in a 66% efficiency at a pressure of 200 kPa and a 98% efficiency when applied a pressure of 50 kPa. Therefore, the use of mullite membranes show limited efficiency towards bacteria retention. Nevertheless, they present fluxes similar to other materials proposed in the literature.

Chemical and Thermal Evaluation of Commercial and Medical Grade PEEK Sterilization by Ethylene Oxide

Many polymers have been used as biomaterials due to their physicochemical characteristics and structural versatility. However, usage on the human body requires sterilization in order to prevent microbial contamination and diminish the risk of rejection or inflammation. This study presents the use of thermogravimetric analysis (TGA) as an alternative to monitor the presence of residual ethylene oxide from polymers sterilization processes. This is a simple technique and does not require sample preparation stages which can imply in some ethylene oxide loss. Ethylene oxide has been used to sterilize polymeric biomaterials, but with restrictions in the amount used due to the difficulty in removing the toxic waste after the sterilization procedure. Samples of commercial (PEEKc) and medical (PEEKm) grade poly(ether ether ketone) (PEEK) were manufactured in the form of cylindrical tubes, hygienized and sterilized with ethylene oxide. PEEKs showed no chemical changes, but exhibited thermal changes by TGA, which evidenced weight loss between 100 and 500oC that was attributed to the removal of residual ethylene oxide, so this technique, at a 10oC‧min-1 heating rate, can be used to monitor the sterilization processes.

Preparation and characterization of composite membranes ceramic/PSf and ceramic/PA 66

ABSTRACT In this paper, ceramic/polymer composite membranes have been prepared to evaluate the efficiency of polymer deposition on the ceramic support from to separation process of Ultrafiltration. Polymers used were polyamide 66 (PA 66) and polysulfone (PSf). The composite membranes were obtained immersing the supports into polymeric solutions to top layer formation. The presence of polymeric layer was observed on the surface of composite membranes by means of the Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Egg albumin (EA) solution was used to determine the rejection of the composite membranes. The ceramic support showed a higher flux value as expected, since its function is to favor flux passage. The composite membrane ceramic/PA 66 showed a higher flux than that of composite membrane ceramic/PSf. The EA rejection measured by reading the absorbance was 14, 42, and 62% to the support, composite membranes ceramic/PSf and ceramic/PA 66, respectively.

Applications of Ceramic Membranes

This chapter presents some of the possible applications shown by ceramic membranes. The following areas will be given emphasis:

Ceramic Membranes Characterization

This chapter is about some of the main methods used in the ceramic membranes characterization. Some of these methods are permeability, solute rejection assays, porosimetry by mercury intrusion, scanning electron microscopy, X-ray diffraction, among others.

Overview Membranes Separations

The technology of membranes separation is a field that involves many processes. These processes are subdivided according to the driving force applied, the feeding phases, the permeate, and the pores’ size.

Ceramic Membrane Modules

Membrane module can be understood as a physical unit, which gathers all the elements that participate in the separation process. Membrane module is, basically, composed by membranes, channels where feed goes through, the permeate and concentrate, and by pressure or current support structures applied to the system.