Degradation In Phosphate Buffer Research Articles

Degradation of nanofiber layers made of biobased polyamide 4

Based on renewable raw materials, polyamide 4 has excellent mechanical properties, high hydrophilicity, and cotton-like water sorption. The problem is its low thermal stability near its melting point, which does not allow melt processing. With the development of the technology of electrostatic spinning of polymers from solutions, the attention of researchers has returned to polyamide 4. In this work, nanofiber layers of polyamide 4 with molar masses of 18,000 and 280,000 g/mol and diameters of 350 ± 60 and 270 ± 10 nm, respectively, were prepared by electrostatic spinning from a mixed solution of formic acid and dichloromethane. Subsequently, the layers were subjected to degradation in phosphate buffer at 37 and 60 °C. The electrostatic spinning process was shown to result in a decrease in the molar mass of the samples. During degradation in buffer at pH 7.4, the molar mass does not change significantly, but there is a change in the structure of the nanofibrous layers by bonding of the fibers, especially for low molecular weight PA4. In contrast to other studies, polyamide 4 is hydrolytically stable even in the form of nanofiber layers.

Oxidation of organic compounds by PMS/CuO system: The significant discrepancy in borate and phosphate buffer

Peroxymonosulfate (PMS)-based advanced oxidation process are widely used in the degradation of organic pollutants. The degradation of the electron-rich azo dye Acid Orange 7 (AO7) through a PMS/CuO heterogeneous system in borate and phosphate buffer were systematically investigated. The CuO was characterized via X-ray diffraction, scanning electron microscopy, fourier-transform infrared spectra, X-ray photoelectron spectroscopy and energy dispersive spectroscopy (SEM-EDS) techniques. The difference of AO7 degradation by PMS/CuO system in borate and phosphate buffer varied with the buffer concentration, PMS concentration, CuO dosage and pH. AO7 degradation fitted well with the pseudo-first order kinetics in these two buffer solutions, the reaction rate constant (kobs) of AO7 degradation in phosphate buffer increased with the increase of phosphate concentration firstly and then reached the maximum value of 0.0123 min−1 at 0.2 M, but it decreased obviously with the increase of borate concentration. It was found that the kobs in two buffers increased linearly with the increase of PMS concentration, and increased with the increase of CuO dosage in borate, while the reaction in phosphate buffer was slightly affected by CuO dosage. Additionally, the kobs increased from 0.0057 min−1 to 0.0487 min−1 with the increase of pH value in phosphate, but decreased gradually with the increase of pH value from 7.0 to 8.5 in borate due to the deprotonation of PMS. Fewer reactive species were produced in phosphate including SO4•–, •OH and 1O2. The conversion between Cu(Ⅱ) and Cu(Ⅰ) was a crucial process for the activation of PMS by CuO in borate, which was hindered in phosphate. This study will provide a reference for the application of different types of buffers in heterogeneous catalysis of PMS.

Enhancement of the permeability and activities of epigallocatechin gallate by quaternary ammonium chitosan/fucoidan nanoparticles

Epigallocatechin gallate (EGCG) has many biological functions; however, the use of EGCG in biomedical and food industries was limited due to its poor oral absorption and high susceptibility to degradation. In this study, a mucoadhesive quaternary chitosan was synthesized and combined with fucoidan (FD) (or depolymerized lower molecular weight fucoidan, LMWF) to prepare EGCG-loaded nanoparticles, which extended EGCG release over 300 min and enhanced the transepithelial permeation of EGCG using Caco-2 cells as a model for intestinal absorption. The nanoparticls protected EGCG against degradation in phosphate buffer (pH 6.8) and the remaining EGCG was 1.7-folds higher than the control (EGCG alone). The additive effects of EGCG combined with FD or LMWF in the nanoparticles increased the DPPH radical scavenging activity and the enzyme inhibitory activity against α-amylase (2.82–4.92 fold increase) and α-glucosidase (1.35–1.67 fold increase), while quaternary chitosan helped to enhance the antibacterial effect of EGCG.

Electrospinning and crosslinking of low-molecular-weight poly(trimethylene carbonate-co-l-lactide) as an elastomeric scaffold for vascular engineering

The growth of suitable tissue to replace natural blood vessels requires a degradable scaffold material that is processable into porous structures with appropriate mechanical and cell growth properties. This study investigates the fabrication of degradable, crosslinkable prepolymers of l-lactide-co-trimethylene carbonate into porous scaffolds by electrospinning. After crosslinking by γ-radiation, dimensionally stable scaffolds were obtained with up to 56% trimethylene carbonate incorporation. The fibrous mats showed Young’s moduli closely matching human arteries (0.4–0.8MPa). Repeated cyclic extension yielded negligible change in mechanical properties, demonstrating the potential for use under dynamic physiological conditions. The scaffolds remained elastic and resilient at 30% strain after 84days of degradation in phosphate buffer, while the modulus and ultimate stress and strain progressively decreased. The electrospun mats are mechanically superior to solid films of the same materials. In vitro, human mesenchymal stem cells adhered to and readily proliferated on the three-dimensional fiber network, demonstrating that these polymers may find use in growing artificial blood vessels in vivo.

Plant Oil Renewable-Resource-based Biodegradable Blends as Green Alternatives in Biopackaging

This preliminary work reports the development of biodegradable films using blends of dehydrated castor oil epoxy (DCOE) with poly (methylmethacrylate) (PMMA) and poly(methacrylic acid) (PMAA). The biodegradability characteristics of the blends were investigated using degradation in phosphate buffer, activated sludge, and soil burial test measurements. The results revealed that the blends with higher content of DCOE underwent higher degradation as compared to the blends with lower DCOE content. Among the DCOE/PMMA and DCOE/PMAA blends, the latter were found to exhibit higher degradation, which was explained with the help of a suitable mechanism.

Compatibility and biodegradability studies of linseed oil epoxy and PVC blends

Abstract With the aim to utilize linseed oil epoxy – a product from sustainable resource for the processing of hard polymers, blends of linseed oil epoxy (LOE) with polyvinylchloride (PVC) were prepared for the first time by solution blending of the requisite amounts of the two components in the weight ratios LOE/PVC- 85/15, 65/35, 55/45, 45/55, 35/65, and 15/85 through solution method by mixing in tetrahydrofuran (THF). The miscibility of the two components in solution phase was investigated by relative viscosity, reduced viscosity and density measurements. The blend with 85 wt% of LOE yielded stiff and flexible films with maximum stress of 33 MPa and 216% elongation at break. Biodegradability of these blends has been studied by soil burial test, enzymatic degradation, and hydrolytic degradation in phosphate buffer. The blend LOE/PVC 85/15 showed the highest biodegradation of 68 wt% in 6 months in the soil burial test. The degradability was found to increase with the increase in LOE content in the blend compositions. The potential applications for such sustainable resource based blend films include packaging materials and biodegradable plastic sheets which can be formed into products such as bio-bags.

High‐performance liquid chromatography/electrospray ionization tandem mass spectrometry for characterization of enzymatic degradation of 2,2′‐bis(2‐oxazoline)‐linked poly‐ε‐caprolactone

This paper describes a straightforward and rapid on-line characterization using high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS(n)) of the enzymatic degradation products of 2,2'-bis(2-oxazoline)-linked poly-epsilon-caprolactone (PCL-O). These new PCL-O polymers are expected to be used in a variety of pharmaceutical and biomedical applications since they are degraded enzymatically by surface erosion. PCL-O was polymerized in a three-step reaction and characterized by (1)H-NMR and size-exclusion chromatography (SEC). Solvent cast polymer films were exposed to enzymatic degradation in phosphate buffer (pH 7.5, 1% pancreatin). The enzymatic degradation of the polymer produced a wide variety of water-soluble oligomers which were separated and identified by HPLC/ESI-MS(n). Optimization of the gradient HPLC method resulted in effective separation of the oligomers. Furthermore, specific structures of the oligomers were clearly identified by tandem mass spectrometry. According to these results, ester bonds seem to be most sensitive to enzymatic degradation and, correspondingly, pancreatic lipase seems to be mainly responsible for the enzymatic erosion of the PCL-O films. This novel mass spectrometric method provides important knowledge about the enzymatic degradation process and structure of the polymer which is difficult to ascertain by other conventional methods.

Synthesis, Characterization and Biodegradation Study of Low Molecular Weight Polyesters

A series of low molecular weight aliphatic biodegradable polyesters were synthesized from 1,3-propanediol and dibasic acids by thermal polycondensation, in the bulk without catalyst in N2 atmosphere at 150°C. The synthesized aliphatic polyesters were characterized by 1H-NMR, FT-IR, solubility, solution viscosity, gel permeation chromatography, and diffential scanning calorimetry. The biodegradability of the synthesized polyester films was tested by enzymatic degradation in phosphate buffer (pH = 7.2) in presence of Rhizopus delemar lipase incubated at 37°C, and soil burial degradation at 30°C. SEM was used to study the surface morphology after incubation of the films. The result of biodegradation shows that the films become brittle on incubation and their surfaces change upon degradation. The biodegradability of the polyesters depends on the crystallinity of the polymers. The degradation was more pronounced in PPSu compared to PPAd.

Biodegradability of PMMA Blends with Some Cellulose Derivatives

High polymer blends of Polymethyl methacrylate (PMMA) with cellulose acetate (CA) and Cellulose acetate phthalate (CAP) of varying blend compositions have been prepared to study their biodegradation behavior and blend miscibility. Films of PMMA–CA, and PMMA–CAP blends have been prepared by solution casting using Acetone and Dimethyl formamide(DMF) as solvents respectively. Biodegradability of these blends has been studied by four different methods namely, soil burial test, enzymatic degradation, and degradation in phosphate buffer and activated sludge degradation followed by water absorption tests to support the degradation studies. Degradation analysis was done by weight loss method. The results of all the tests showed sufficient biodegradability of these blends. Degradability increased with the increase in CA and CAP content in the blend compositions. The miscibility of PMMA–CA and PMMA–CAP blends have been studied by solution viscometric and ultrasonic methods. The results obtained reveal that PMMA forms miscible blends with either CA or CAP in the entire composition range. Miscibility of the blends may be due to the formation of hydrogen bond between the carbonyl group of PMMA and the free hydroxyl group of CA and CAP.

Study of NADH Stability Using Ultraviolet–Visible Spectrophotometric Analysis and Factorial Design

The chemical stability of nicotinamide adenine dinucleotide coenzyme (NADH/NAD+) and its deriva-tives (NADPH/NADP+) was investigated using changesin the UV–visible absorption spectra of these compounds. The spectra of cofactor (reduced form) were monitored at 340 nm wavelength in different buffers, showing a faster degradation in phosphate buffer. This was assigned to the adduct formation between phosphate and NADH (pyridine ring). The three-factor–two-level factorial design study evaluated the contributions: buffers (phosphate and Pipes 0.1 M), pH's (6.8 and 7.8), and temperature (25 and 30°C). The freshly prepared aqueous solutions of coenzyme were analyzed after 40 min under the different conditions (eight assays in triplicate) of the experiment. The main observed effects of the NADH oxidation were, in increasing order, pH, temperature, and buffer without appreciable interactive effects. Therefore, it was verified that the better conditions for cofactor use were alkaline media employing Pipes buffer or its derivatives and low temperatures.

Degradation behaviour of poly (methyl methacrylate- g-3-hydroxybutyrate) polymer films

Poly(methyl methacrylate- g-3-hydroxybutyrate) films were prepared from new graft polymers synthesised by an anionic grafting reaction of 3-butyrolactone (3-BL) on poly(methyl methacrylate) (PMMA). The resulting graft polymers form a transparent film of a one phase system, as revealed by DSC measurements. A plasticisation effect was observed for film samples containing the PBL grafted chains. This effect increased with increasing amount of PBL in the graft copolymer. The mechanical properties of the films were investigated, and thermal, hydrolytic and enzymatic degradation behaviours were evaluated. Disintegration of the films was observed during their hydrolytic degradation in phosphate buffer.

Degradation of polydispersed poly( l-lactic acid) to modulate lactic acid release

Polydispersed poly( l-lactic acid) (PLLA) membranes comprised of blends of monodispersed PLLA of weight average molecular weight of 82500 and 7600 were fabricated to investigate the effect of polydispersity on degradation characteristics. The PLLA blends exhibited large spherulites of high molecular weight chains embedded in a low molecular weight matrix. During degradation in phosphate buffer at pH 7.4 and 37 °C for 28 d, the release rate of lactic acid increased as the percentage of the low molecular weight component in the blend was increased. For low molecular weight compositions larger than 50%, voids were created in the degrading blends due to the degradation of low molecular weight chains and the concurrent dissolution of lactic acid, and also the release of undegraded particles of high molecular weight. These studies demonstrate the feasibility of modulating lactic acid release during in vivo degradation of PLLA implants by adjusting the polymer polydispersity.

Development and evaluation of microscale apparatus for the generation of kinetic data at high temperatures, applied to the degradation of thiamine

A microminiaturized tubular heating system, with continuous heating and cooling, for kinetic studies has been developed. The apparatus was used in the temperature range from 110 to 160 °C. Heating to holding temperature and cooling to room temperature was accomplished in one second. The sample was injected into the apparatus with an HPLC loop injector. After thermal treatment, a well-defined fraction was withdrawn by a fraction collector. The sample dilution during thermal processing was corrected against an inert standard. A kinetic study of thiamine degradation in phosphate buffer at pH 7 was performed to evaluate the apparatus. The activation energy ( E a) of the thermal degradation of thiamine was determined to be 119 kJ mol ( r = −0.9981).

Sputtered dielectric capacitors : E. E. Smith and S. G. Ayling, Proc. 1962 Electronic Components Conference, Washington D.C., p. 82 (May 1962)

A microminiaturized tubular heating system, with continuous heating and cooling, for kinetic studies has been developed. The apparatus was used in the temperature range from 110 to 160 °C. Heating to holding temperature and cooling to room temperature was accomplished in one second. The sample was injected into the apparatus with an HPLC loop injector. After thermal treatment, a well-defined fraction was withdrawn by a fraction collector. The sample dilution during thermal processing was corrected against an inert standard.A kinetic study of thiamine degradation in phosphate buffer at pH 7 was performed to evaluate the apparatus. The activation energy (Ea) of the thermal degradation of thiamine was determined to be 119 kJmol (r = −0.9981).