ENCAPSULATION OF PARTIALLY PURIFIED BROMELAIN FROM PINEAPPLE CORES IN ALGINATE-PECTIN BEADS AS A TARGETED ANTIPLATELET AGENT

Objective: Oral administration of bromelain can decrease its bioactivity once it makes contact with stomach acid. Therefore, bromelain was loaded into alginate (Alg), pectin (Pec), and alginate-pectin (AP) beads to control its release into the intestines and avoid degradation. Methods: Crude bromelain was purified by ammonium sulfate precipitation and the dialysis process. In vitro releases and kinetics studies of bromelain-loaded alginate-pectin beads were carried out using an acid and phosphate buffer medium. The beads were characterized using physical analysis, Fourier-Transform Infrared Spectroscopy (FTIR) analysis, and Differential Scanning Calorimetry (DSC) analysis. Results: The dialysis fraction of bromelain has a specific activity of 67.93 U/mg, 3.05 times that of crude bromelain. That fraction was encapsulated in Alg, Pec, and AP beads with a range of encapsulation efficiency around 82.70–91.39%. Bromelain-loaded pectin and AP19 beads were chosen to study in an in vitro release based on their swelling properties and encapsulation efficiency. Bromelain-loaded AP19 beads have lower release than bromelain-loaded pectin beads in both dissolution mediums. The cumulative releases of AP19 are 9.99 and 87.81% in 0.1 N HCl and phosphate buffer medium, respectively. Bromelain-loaded P and AP beads both follow the zero-order kinetics model and the dissolution mechanism of the beads is non-Fickian with a combination of diffusion and erosion. The in vitro antiplatelet activity of dissolution aliquots (20.51 and 18.48%) is lower than its dialysis fraction (56.04%). Conclusion: This in vitro research data shows promising potency for AP as a carrier for oral administration of bromelain as an antiplatelet agent.

Biocatalyzed Redox Processes Employing Green Reaction Media

The application of biocatalysts to perform reductive/oxidative chemical processes has attracted great interest in recent years, due to their environmentally friendly conditions combined with high selectivities. In some circumstances, the aqueous buffer medium normally employed in biocatalytic procedures is not the best option to develop these processes, due to solubility and/or inhibition issues, requiring biocatalyzed redox procedures to circumvent these drawbacks, by developing novel green non-conventional media, including the use of biobased solvents, reactions conducted in neat conditions and the application of neoteric solvents such as deep eutectic solvents.

Efficient Biocatalytic Preparation of Optically Pure (R)-1-[4-(Trifluoromethyl)phenyl]ethanol by Recombinant Whole-Cell-Mediated Reduction

(R)-1-[4-(Trifluoromethyl)phenyl]ethanol is an important pharmaceutical intermediate of a chemokine CCR5 antagonist. In the present study, a bioprocess for the asymmetric reduction of 4-(trifluoromethyl)acetophenone to (R)-1-[4-(trifluoromethyl)phenyl]ethanol was developed by recombinant Escherichia coli cells with excellent enantioselectivity. In order to overcome the conversion limitation performed in the conventional buffer medium resulting from poor solubility of non-natural substrate, we subsequently established a polar organic solvent-aqueous medium to improve the efficacy. Isopropanol was selected as the most suitable cosolvent candidate, based on the investigation on a substrate solubility test and cell membrane permeability assay in different organic solvent-buffer media. Under the optimum conditions, the preparative-scale asymmetric reduction generated a 99.1% yield with >99.9% product enantiomeric excess (ee) in a 15% (v/v) isopropanol proportion, at 100 mM of 4-(trifluoromethyl)acetophenone within 3 h. Compared to bioconversion in the buffer medium, the developed isopropanol-aqueous system enhanced the substrate concentration by 2-fold with a remarkably improved yield (from 62.5% to 99.1%), and shortened the reaction time by 21 h. Our study gave the first example for a highly enantioselective production of (R)-1-[4-(trifluoromethyl)phenyl]ethanol by a biological method, and the bioreduction of 4-(trifluoromethyl)acetophenone in a polar organic solvent-aqueous system was more efficient than that in the buffer solution only. This process is also scalable and has potential in application.

H/D Isotope Effects on Redox-Switching of DNA Self-Assembled Monolayers Observed by EQCM and Cyclic Voltammetry

An electrochemical quartz crystal microbalance (EQCM) was employed to study the interactions of hexammine ruthenium(III) (RuHex) and hexammine cobalt(III) (CoHex) with a mixed self-assembled monolayer of single-stranded DNA and 6-mercapto-1-hexanol (ssDNA/MCH SAM) immobilized on gold electrodes. When the buffer medium was switched to deuterium oxide (D₂O) from normal water (H₂O), we observed a pronounced H/D kinetic isotope effect where a consistent shift of up to 400 mV was seen for the reduction peak potential of CoHex but not with RuHex. This was attributed to a 2400-fold change of the apparent reaction rate constant. Though there was a dramatic increase in the EQCM frequency response at a millisecond time scale in the presence of both redox indicators, compared to the signal observed in a low ionic strength buffer (10 mM tris(hydroxymethyl)aminomethane (Tris)/H₂SO₄at pH 7.5), a 10 Hz decrease in the frequency shift was observed upon switching from H₂O to D₂O-based buffer medium. The hydrogen bond network within the ssDNA layer seems to amplify the H/D isotope effect with CoHex. Amplified isotope effects may play a role in living systems. The mechanisms of recently reported H/D isotope effects in medicinal and biochemistry are still widely unclear. Voltammetric and EQCM studies of H/D isotope effects can provide a platform to investigate amplified isotope effects not only with DNA layers, but probably also with proteins and small organic molecules and may be useful for studies of cell proliferation, as well as drug testing.

H/D Isotope Effects on Redox-Switching of DNA Self-Assembled Monolayers Observed by EQCM and Cyclic Voltammetry

An electrochemical quartz crystal microbalance (EQCM) was employed to study the interactions of hexammine ruthenium(III) (RuHex) and hexammine cobalt(III) (CoHex) with a mixed self-assembled monolayer of single-stranded DNA and 6-mercapto-1-hexanol (ssDNA/MCH SAM) immobilized on gold electrodes. When the buffer medium was switched to deuterium oxide (D₂O) from normal water (H₂O), we observed a pronounced H/D kinetic isotope effect where a consistent shift of up to 400 mV was seen for the reduction peak potential of CoHex but not with RuHex. This was attributed to a 2400-fold change of the apparent reaction rate constant. Though there was a dramatic increase in the EQCM frequency response at a millisecond time scale in the presence of both redox indicators, compared to the signal observed in a low ionic strength buffer (10 mM tris(hydroxymethyl)aminomethane (Tris)/H₂SO₄at pH 7.5), a 10 Hz decrease in the frequency shift was observed upon switching from H₂O to D₂O-based buffer medium. The hydrogen bond network within the ssDNA layer seems to amplify the H/D isotope effect with CoHex. Amplified isotope effects may play a role in living systems. The mechanisms of recently reported H/D isotope effects in medicinal and biochemistry are still widely unclear. Voltammetric and EQCM studies of H/D isotope effects can provide a platform to investigate amplified isotope effects not only with DNA layers, but probably also with proteins and small organic molecules and may be useful for studies of cell proliferation, as well as drug testing.

Kinetics and mechanism of the reduction of n-(2-hydroxyethyl)ethylenediaminetriacetatoiron(III) complex by thioglycol in bicarbonate buffer medium

The kinetics and mechanism of reduction of N-(2-hydroxyethyl) ethylenediaminetriacetatoiron (III) complex (hereafter [Fe(III)HEDTAOH2]) by thioglycol (hereafter RSH) has been studied spectrophotometrically in a bicarbonate buffer medium. The study was carried out under pseudo-first order conditions of an excess of thioglycol concentration at 28 ± 1℃, I = 0.44 mol dm-3 (KNO3) and λmax = 490 nm. The reaction is first order in [Fe(III)HEDTAOH2] and half order in [RSH] and a stoichiometric mole ratio of [Fe(III)HEDTAOH2]: RSH is 2:1. Reaction rates increased with increase in ionic strength (I) and dielectric constant (D) of the reaction medium of the reaction. The reaction displayed positive primary salt effect, which suggests the composition of activated complex are likely charged reactants ions. Test for possibility of an intermediate complex formation shows negative as Michaelis-Menten plot was linear with very negligible intercept. Based on the findings, outer-sphere mechanism is proposed for the reaction. The experimental rate law obtained is; - = k2 [Fe(III)HEDTAOH2][RSH]½

Improving Vaccine Safety by Using an Algorithmic Model as a Replacement for a Physical Thermal Buffer

Conventional practice in vaccine storage is to insert a temperature probe into a bottle of glycol, or another equivalent thermal buffer medium, to simulate the temperature experience of the stored vaccine, rather than just the air temperature. Such a thermal buffer is intended to reduce false alarms so that the drug manager will know with higher confidence that a temperature alert is an event requiring action. While necessary and appropriate to correctly monitor the storage conditions, it is a practice that is messy, inconvenient, and costly, and can result in reports that diverge from the actual experience of the stored inventory. This paper explores the use of a mathematical algorithm to reproduce the behavior of a physical thermal buffer medium. The paper describes the algorithm and reports the degree to which it accurately simulates the experience of a 20-ml glycol container. The algorithm is shown to be highly predictive of the temperatures measured inside a container containing glycol.