Gram Of Matrix Research Articles

Influence of the chemical composition and structure design of electrospun matrices on the release kinetics of Aloe vera extract rich in aloin

The release kinetics of bioactive agents from electrospun matrices is governed by several factors, such as the chemical composition and design of the release device. In this work, three different chemical formulations and two different product designs were developed to control the release of Aloe vera extract rich in aloin to skin lesions. The kinetics of aloin release from single layer electrospun materials formulated with polymers with different biodegradation rates (isolated PCL and PCL blended with PLLA or PDLG) was analyzed and compared to the behavior of a three-layer sequential electrospun PCL matrix in which only the intermediate layer contained the A. vera extract (PCL SW). The multilayered structure with the physically confined bioactive agent layer had the purpose then of both modulating aloin release and also of protecting it from direct light exposure. Thin films were obtained, all presenting high potential to be used as wound dressing components, with thickness values of 0.13–0.26 mm and homogeneous fibrous microstructure, capable of absorbing from 1.06 to 2.88 g of phosphate buffered saline per gram of matrix. The films were stable in the same buffer, showing a maximum mass loss of less than 8% after 7 days. The biomaterials presented tensile strength of 0.64–1.37 MPa and elongation at break of 277–375%. The most striking difference in behavior was in the release kinetics, which was much more controlled with the PCL SW structure than with the others, in which marked burst effect was observed. In this film, the release mechanism was associated with the diffusion of the bioactive agent, having also contributions from the electrospun matrix relaxation and dissolution.

Optimized structured sparse sensing matrices for compressive sensing

Abstract We consider designing a robust structured sparse sensing matrix consisting of a sparse matrix with a few non-zero entries per row and a dense base matrix for capturing signals efficiently. We design the robust structured sparse sensing matrix through minimizing the distance between the Gram matrix of the equivalent dictionary and the target Gram of matrix holding small mutual coherence. Moreover, a regularization is added to enforce the robustness of the optimized structured sparse sensing matrix to the sparse representation error (SRE) of signals of interests. An alternating minimization algorithm with global sequence convergence is proposed for solving the corresponding optimization problem. Numerical experiments on synthetic data and natural images show that the obtained structured sensing matrix results in a higher signal reconstruction than a random dense sensing matrix.

Wrinkled Silica Nanoparticles: Efficient Matrix for β-Glucosidase Immobilization

β-Glucosidase (BG) was immobilized by adsorption on wrinkled silica nanoparticles (WSNs) giving an active and stable biocatalyst for the hydrolysis of cellobiose. WSNs exhibiting both a central-radial pore structure and a hierarchical trimodal micro-/mesoporous pore size distribution were synthesized. They were used as a matrix to immobilize BG, obtaining a biocatalyst (BG/WSNs) containing 150 mg of enzyme per gram of matrix. A complete textural and morphological characterization of BG/WSNs performed by the Brunauer–Emmett–Teller (BET) method, thermogravimetric (TG), Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) analyses showed that this matrix can generate a microenvironment particularly suitable for this enzyme. The immobilization procedure used allowed preserving most of the secondary structure of the enzyme and, consequently, its catalytic activity. The kinetic parameters of the cellobiose hydrolysis performed with the biocatalyst were determined and compared with thos...

Enzyme immobilization on smart polymers: Catalysis on demand

A new approach for the synthesis of hydrogel films with thermo-sensitive enzymatic activity is reported. Pepsin (PEP) was covalently immobilized on thermo-responsive hydrogels by radical polymerization in the presence of N-isopropylacrylamide and poly-(ethylene glycol) dimethacrylate 750, acting as functional monomer and crosslinking agent, respectively. Hydrogels showing lower critical solution temperatures between 32.9 and 36.1°C were synthesized by UV-irradiation of reaction batches differing in the PEP/monomers ratio. The derivatization degree of the hydrogels was expressed as mg of PEP per gram of matrix and found to be in the range of 6 to 11% as assessed by Lowry method. Scanning electron microscopy analysis and water affinity evaluation allowed to highlight the porous morphology and thermo-responsivity of hydrogels as a function of temperature. Using bovine serum albumin as a substrate, kinetics parameters were determined by Lineweaver–Burk plots and the catalyst efficiency evaluated. The influence of temperature on enzyme activity, as well as the thermal stability and reusability of devices, were also investigated.

Raman Spectroscopic Detection of Anthrax Endospores in Powder Samples

Polymerase chain reaction (PCR) is becoming the method of choice for detecting microorganisms concealed in complex matrices or “hoax materials” like household dry powders, food, and soil.[1] However, adding samples directly to a PCR reaction is in most cases not possible because of the presence of PCR inhibitors in the sample.[2] Thus, in order to reliably use PCR, one must either enrich the culture prior to the analysis, which is time-consuming for fastidious organisms, or extract the total DNA directly from the sample, which requires an extraction technique capable of processing different sample types. However, since most DNA extraction methods are often not generic in that sense, they lead to unreliable DNA recovery yields.[2, 3]

Immobilized copper-ion affinity adsorbent based on a cross-linked β-cyclodextrin polymer for adsorption of Candida rugosa lipase

Lipase from Candida rugosa was immobilized on a β-cyclodextrin-based polymer by adsorption and subsequent cross-linking with epichlorohydrin (EP-CD). The ligand iminodiacetic acid (IDA) was then bonded with the cross-linked β-cyclodextrin (EP-CD-IDA). This affinity adsorbent was further chelated with Cu2 + for the purpose of binding affinity and stability. The properties of the immobilized lipase were assayed and compared with those of the free enzyme. Results showed that 266 µg protein with an activity of 17.85 U was bound per gram of matrix, giving 188% of the specific activity of the free enzyme and a total recovered activity of 79.7% under the optimum conditions. The pH and thermal stabilities of lipase were improved after immobilization on the β-cyclodextrin-based polymer (EP-CD-IDA-Cu2 +). In addition, experimental results indicated that the residual activity of the immobilized lipase was 50% after eight cycles of reuse.

Lycopene and β-Carotene Extraction from Tomato Processing Waste Using Supercritical CO2

Tomato skins and their mixtures with seeds were submitted to supercritical CO2 extraction using a flow apparatus at pressures of 250 and 300 bar and temperatures of 60 and 80 °C. Two different mean particle sizes (80 and 345 μm) were used at two solvent flow rates (0.792 and 1.35 kg/h). The yields of lipids, lycopene, and β-carotene obtained by supercritical fluid extraction were compared with those obtained by conventional organic solvent extraction. Supercritical fluid extraction from tomato skins at 300 bar and 80 °C allowed the recovery of 80% of the lycopene and 88% of the β-carotene, using about 130 g of CO2 per gram of matrix at the lower flow rate of CO2.

Egg-matrix for large-scale single-step affinity purification of plant lectins with different carbohydrate specificities

Hen eggs represent an easily available and inexpensive source of glycoproteins expressing a variety of sugars. Egg glycoproteins might therefore be exploited to purify by affinity chromatography carbohydrate-binding proteins (lectins) with different specificities. A method to generate an affinity matrix from hen eggs is described. The matrix was assayed for its ability to purify in a single step biologically active phytohemagglutinin, wheat germ agglutinin, lentil lectin, and peanut agglutinin. Milligrams of purified lectins per gram of matrix was obtained, with the only exception of peanut agglutinin that was not efficiently retained into the affinity column. Hen egg chromatography is a relatively simple, fast, and reproducible method to purify high amount of plant lectins.

Levan production by use of the recombinant levansucrase immobilized on titanium-activated magnetite

Levansucrase from Zymomonas mobilis expressed in Escherichia coli was immobilized onto the surface of magnetite. Optimum conditions for the immobilization were, pH 4.0; immobilization reaction time of 30 min and 8 U of enzyme per gram of matrix. Immobilization yield was 75% under optimized conditions. The maximum production yield of levan by the immobilized levansucrase was about 42% on a fructose released basis with sucrose as substrate at 100 g/l. Thermal stability of the levansucrase increased by immobilization procedure. Furthermore, immobilized enzyme showed the less polymerizing activity in levan formation, producing the low-molecular weight (MW) levan. The molecular weight of levan can be controlled by using the immobilized levansucrase in high yield. Immobilized levansucrase retained 61% of the original activity after five repeated uses.