Exploration of solvent casting for designing engineered microstructures for biomedical and functional applications

In this paper, we report the synthesis and characterization of composites of bioplastics (Poly-lactic Acid (PLA), Polyhydroxyalkaonate (PHA), and PLA-PHA blends) filled with dried grains with solubles (DDGS) and hydroxyapatite (HAP) by using a solvent casting process. Detailed microstructural, thermal, and mechanical characterization is presented in the text. At low concentrations of HAP (5–10 vol%) and DDGS (5–31 vol%) additions, the bioplastic films had mechanical integrity, but the ultimate tensile strength (UTS) decreased after the addition of DDGS and HAP reinforcements due to poor adhesion between the bioplastics and fillers. In the intermediate concentration, pre-pregnated chips of DDGS (31–51 vol%)-bioplastics and HAP (30–50 vol%)-bioplastics with dichloromethane (DCM) were partially dried and then hot-pressed to produce bulk samples (HPC-process). The addition of bioplastics improved the plasticity of DDGS-bioplastics composites. The HAP-bioplastics composites showed polymer dependent response, for example the ultimate compressive strength (UCS) of 50%HAP-PLA, and 30%HAP-PLA were 77.6 ± 10.2 and 97.7 ± 5.9 MPa, respectively which are comparable to bone. The DDGS additions increased the hydrophilicity of PLA, PHA, and PLA-PHA blend. For comparison, HAP increased the hydrophilicity of PHA and PLA-PHA blends. At higher concentration (bioplastics with 70 vol% HAP additions), the films converted into microencapsulated HAP particles with bioplastics by a simple milling process thus eliminating the need for emulsions and/or surfactants during the microencapsulation process.     

Simultaneous Measurement of Titratable Acidity and Fermentation Index in Cocoa Beans by Electronic Tongue Together with Linear and Non-linear Multivariate Technique

Titratable acidity (TA) and fermentation index (FI) are important quality indicators of cocoa beans. This paper attempted the simultaneous analysis of these indicators by electronic tongue (ET) and two multivariate calibrations. ET was used for data acquisition, while partial least squares (PLSs) and principal component support vector machine regression (PC-SVMR) were used to build the calibration models. Some parameters were optimized simultaneously by leave-one-out cross-validation (LOOCV) in calibrating the model. The performance of the model was tested according to root mean square error of prediction (RMSEP) and correlation coefficient (R _pre) in the prediction set. The results revealed that PC-SVMR model was superior to PLS model in this work. The optimal PC-SVMR model for TA was R _pre?=?0.960 and RMSEP?=?0.0077, while for FI, this was R _pre?=?0.954 and RMSEP?=?0.058. This study demonstrated that ET together with SVMR could be used to analyze titratable acidity and fermentation index in cocoa beans for quality control purposes.     

Aptamers: an emerging class of bioaffinity ligands in bioactive peptide applications

Abstract

The food and health applications of bioactive peptides have grown remarkably in the past few decades. Current elucidations have shown that bioactive peptides have unique structural arrangement of amino acids, conferring distinct functionalities, and molecular affinity characteristics. However, whereas interest in the biological potency of bioactive peptides has grown, cost-effective techniques for monitoring the structural changes in these peptides and how these changes affect the biological properties have not grown at the same rate. Due to the high binding affinity of aptamers for other biomolecules, they have a huge potential for use in tracking the structural, conformational, and compositional changes in bioactive peptides. This review provides an overview of bioactive peptides and their essential structure–activity relationship. The review further highlights on the types and methods of synthesis of aptamers before the discussion of the prospects, merits, and challenges in the use of aptamers for bioaffinity interactions with bioactive peptides.     

Fenton-driven regeneration of MTBE-spent granular activated carbon—Effects of particle size and iron amendment procedures

Fenton-driven regeneration of spent granular activated carbon (GAC) can be used to regenerate organic contaminant-spent GAC. In this study, the effects of GAC particle size (>2 mm to <0.35 mm) and acid pre-treatment of GAC on Fenton-driven oxidation of methyl-tert-butyl ether (MTBE)-spent GAC were evaluated. Iron (Fe) was amended to the GAC using two methods: (1) untreated—where GAC was amended with a concentrated solution of ferrous sulfate and (2) acid pre-treatment—where GAC was amended with acid followed by sequential applications of a dilute ferrous sulfate solution. Subsequently, MTBE was amended to the GAC, followed by oxidative treatments with H₂O₂. H₂O₂ reaction and MTBE oxidation were inversely correlated with GAC particle size and were attributed to shorter intraparticle diffusion transport distances for both H₂O₂ and MTBE. Image analysis of the GAC cross-sections (i.e., prepared thin sections) revealed that the Fe amended to the GAC extended to the center of the GAC particles. Fe accumulated at higher levels on the periphery of the untreated GAC but Fe dispersal was more uniform in the acid pre-treated GAC. In the acid pre-treated GAC, conditions for MTBE oxidation were favorable and greater levels of MTBE oxidation were measured for all particle size fractions tested. Modeling and critical analysis of H₂O₂ diffusive transport and reaction indicated limited H₂O₂ penetration into large GAC particles which contributed to a decline in MTBE removal. Residual MTBE remaining on the GAC limited the quantity of MTBE that could be re-adsorbed, but no reduction in MTBE sorption capacity resulted from oxidative treatments.     

Detergent binding in trigonal crystals of OmpF porin from Escherichia coli

The structure of the detergent, ocytyl hydroxyethylsufoxide (C8(HE)SO), bound to the OmpF porin from E coli (in the trigonal crystal form) has been determined by neutron crystallography. Due to a dynamic exchange of detergent molecules with their environment they are not ordered on an atomic scale. The structure reported here is therefore at a resolution of approximately 16 A. The X-ray crystallographically determined structure of the protein provides a starting point for the neutron analysis in which the detergent is visualized primarily thanks to its high contrast against D2O. The structure shows the detergent to be located mainly in two areas. It forms toroidal annuli around each OmpF trimer, these annuli fusing to form a detergent belt surrounding a solvent filled column traversing the crystal. Those areas of the protein to which the detergent binds are formed almost exclusively of hydrophobic residues and form a band about 30 A high around the trimer. Its upper and lower bounds are defined by two bands of aromatic residues, tyrosines pointing away from the detergent belt and interacting with the polar headgroups while phenylalanines point inwards. This strongly suggests that the same areas define, in vivo, the location at which protein interacts with lipid. The hydrophobic moiety of detergent is also found mediating the hydrophobic protein-protein interactions at the interface between two trimers on the crystallographic two-fold axis.     

Radioactivity and dose assessment of marble samples from Igbeti mines, Nigeria

The concentration and distribution of natural radionuclides in marble around Igbeti marble mines, Nigeria, were measured to evaluate the environmental radioactivity and health effects which the marble samples may posses. The concentration of radionuclides was determined using gamma-ray spectrometry with NaI (Tl) detector. The measured values of the activities of (226)Ra, (232)Th and (40)K in the marble samples were found to lie in the ranges 2.0-2.7, 0.3-1.2 and 5.7-7.3 Bq kg(-1), respectively. The samples were also found to have radium equivalent activity in the range 3.4-4.6 Bq kg(-1), external hazard indices of 0.009-0.012 and internal hazard indices of 0.014-0.019. The estimated representative (I(gammar)) hazard index is 0.028. The measurements show that marble samples from Igbeti mine have low level of natural radioactivity and therefore the use of these types of marble in construction of dwellings is safe for inhabitants.     

Identifying individual single-walled and double-walled carbon nanotubes by atomic force microscopy

We show that the number of concentric graphene cylinders forming a carbon nanotube can be found by squeezing the tube between an atomic force microscope tip and a silicon substrate. The compressed height of a single-walled nanotube (double-walled nanotube) is approximately two (four) times the interlayer spacing of graphite. Measured compression forces are consistent with the predicted bending modulus of graphene and provide a mechanical signature for identifying individual single-walled and double-walled nanotubes.     

Nozzle flow behavior of aluminum/polycarbonate composites in the material extrusion printing process

This article investigates the effects of nozzle diameter, resin viscosity, and filler size and volume content on the melt flow properties and clogging of composites in the material extrusion additive manufacturing process. The flow behavior was systematically characterized by a custom nozzle flow test (NOFT) device, thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Results indicated that the viscosity of the material, the particle size, and the diameter of the nozzle were important factors for clogging. TGA results showed deviations from the designed filler volume fraction, which could be due to the buildup of filler material in the nozzle and subsequent partial clogging. SEM observations showed that particle agglomeration tended to be more prevalent in strands with high filler volume content. The agglomeration could be seen near the edge of the strand. A model for the clogging formation in NOFT was summarized into four stages: particle deposition on the wall of the nozzle, creation of dendrites, particle agglomeration, and particle clogging, which explained the clogging mechanism in the NOFT. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47252.