Degradation and detoxification of ribavirin by UV/chlorine/Fe(II) process in water treatment system.

Ribavirin (RBV), which is extensively used to treat viral diseases such as COVID-19, is considered one of the major emerging contaminants due to its long-term existence and health risk in the aqueous environmental system. However, research on effective removal of RBV still remains insufficient. In this study, we investigated the RBV degradation kinetics and mechanism in UV/chlorine/Fe(II) process. The degradation rate constant kobs-RBV of RBV was 2.52 × 10-4 s-1 in UV/chlorine/Fe(II) process, which increased by 1.6 times and 1.3 times than that in chlorine alone and UV/chlorine process, respectively. Notably, trace amount Fe(II) promoted RBV degradation in UV/chlorine system through Fe2+/Fe3+ cycles, enhancing the yield of reactive species such as HO· and certain species reactive chlorine radicals (RCS). The contributions of HO· and RCS toward RBV degradation were 53.91% and 16.11%, respectively. Specifically, Cl·, ClO·, and Cl2·- were responsible for 8.59%, 2.69%, and 4.83% of RBV removal. The RBV degradation pathway indicated that the reactive species preferentially attacked the amide moiety of RBV, which cleaved the ether bond and the hydroxyl group. The toxicity evaluation of RBV degradation products elucidated that UV/chlorine/Fe(II) process was beneficial for RBV detoxification.

Positive profile of natural small molecule organic matters on emerging antivirus pharmaceutical elimination in advance reduction process: A deep dive into the photosensitive mechanism of triplet excited state compounds.

Natural small molecular organic matter (NSOM), ubiquitous in natural waters and distinct from humic acid or fulvic acid, is a special type of dissolved organic matter (DOM) which is characterized as strong photosensitivity and simple molecular structure. However, little study had been directed on the role of NSOM in eliminating emerging contaminants in advanced reduction process (ARP). This study took three small molecular isomeric organic acids (p-hydroxybenzoic acid, pHBA; salicylic acid, SA; m-hydroxybenzoic acid, mHBA) as the representative substances of NSOM to explore these mechanisms on promoting Ribavirin (RBV, an anti COVID-19 medicine) degradation in ultraviolet activated sulfite (UV/Sulfite) process. The results demonstrated that the observed degradation rate constant of RBV (kobs-RBV) was 7.56 × 10-6 s-1 in UV/Sulfite process, indicating that hydrated electron (eaq-) from UV/Sulfite process could not effectively degrade RBV, while it increased by 178 and 38 times when pHBA and SA were introduced into UV/Sulfite process respectively, suggesting that pHBA and SA strongly promoted RBV degradation while mHBA had no promotion on RBV abatement in UV/Sulfite process. Transient absorption spectra and reactive intermediates scavenging experiment indicated that the triplet excited state pHBA and SA (3pHBA* and 3SA*) contributed to the degradation of RBV through non-radical process. Notably, eaq- played the role of key initiator in transforming pHBA and SA into their triplet states. The difference of kobs-RBV in UV/Sulfite/pHBA and UV/Sulfite/SA process was attributed to different generation pathways of 3pHBA* and 3SA* (high molar absorptivity at the wavelength of 254 nm and photosensitive cycle, respectively) and their second order rate constants towards RBV (kRBV-3pHBA* = 8.60 × 108 M-1 s-1 and kRBV-3SA* = 6.81 × 107 M-1 s-1). mHBA could not degrade RBV for its lack of intramolecular hydrogen bond and low molar absorptivity at 254 nm to abundantly transform into its triplet state. kobs-RBV increased as pH increased from 5.0 to 11.0 in UV/Sulfite/SA process, due to the high yield of eaq- in alkaline condition which promoted the generation of 3SA* and the stable of the absorbance of SA at 254 nm. By contrast, kobs-RBV underwent a process of first increasing and then decreasing in UV/Sulfite/pHBA process as the increase of pH, and its highest value achieved in a neutral condition. This lied in the exposure of eaq- increased as the increase of pH which promoted the generation of 3pHBA*, while the molar absorptivity of pHBA at 254 nm decreased as the increase of pH in an alkaline condition which inhibited the yield of 3pHBA*. The RBV degradation pathways and products toxicity assessment indicated that UV/Sulfite/pHBA had better detoxification performance on RBV than UV/Sulfite/SA process. This study disclosed a novel mechanism of emerging contaminants abatement through non-radical process in NSOM mediated ARP, and provide a wide insight into positive profile of DOM in water treatment process, instead of only taking DOM as a quencher of reactive intermediates.

Role of trace TEMPO as electron shuttle in enhancing chloroquine phosphate elimination in UV-LED-driven persulfate activation process.

Chloroquine Phosphate (CP) is an antiviral drug used for treatment of COVID-19. It is released into wastewater and eventually contaminates natural water. This study reports an effective homogeneous catalysis way for CP degradation by the 2,2,6,6-Tetramethylpiperidine-N-oxyl (TEMPO) enhanced persulfate (PDS) activation under UVB-LEDs irradiation at 305 nm. TEMPO at a low concentration (0.1 µM) enhanced CP degradation in UV305/PDS process in deionized water at different pHs, in different anions and different molecular weight dissolved organic matter solutions and in real surface water. The enhancement was verified to be attributed to the electron shuttle role of TEMPO, which promoted the yield of SO4 •- by enhancing electron donating capacity of the reacting system. The degradation products of CP and their acute toxicities suggested that UV305/PDS/TEMPO process has better performance on CP detoxification than UV305/PDS process. This study provides a new way to tackle the challenge of pharmaceutical pollutions in homogeneous photocatalysis process for natural water and sewage restoration.

The role of trace N-Oxyl compounds as redox mediator in enhancing antiviral ribavirin elimination in UV/Chlorine process.

Ribavirin (RBV) is an antiviral drug used for treating COVID-19 infection. Its release into natural waters would threaten the health of aquatic ecosystem. This study reports an effective approach to degrade RBV by the trace N-oxyl compounds (2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) and N-Hydroxyphthalimide (NHPI)) enhanced UV activated free chlorine (UV/Chlorine) process. The results indicated that TEMPO and NHPI at low concentrations (0.1 µM and 1 µM, respectively) could strongly enhance RBV degradation in both deionized water with different pHs and practical surface water. The enhancement was verified to be attributed to the transformation of TEMPO and NHPI into their reactive forms (i.e., TEMPO+ and PINO), which generations deeply relied on radicals. The two N-oxyl compounds inhibit ClO• yield by hindering the reaction of free chlorine vs. HO• and Cl•. The analyses on acute toxicities of RBV degradation products indicate that UV/Chlorine/N-oxyl compounds process can detoxify RBV more efficiently than UV/Chlorine process.

In vitro drug permeation enhancement potential of aloe gel materials.

Aloe vera gel previously showed the ability to increase the bioavailability of vitamins and to enhance the in vitro transport of a macromolecular drug across intestinal epithelial cell monolayers. The purpose of this study is to investigate the potential of other species of aloe to act as drug absorption enhancement agents. The effect of gel materials from three South African aloes; Aloe ferox, A. marlothii and A. speciosa on the transepithelial electrical resistance and permeability of atenolol across excised intestinal tissue of the rat as well as the transport of FITC-dextran across Caco-2 cell monolayers was investigated. The aloe gel materials exhibited the ability to statistically significantly reduce the transepithelial electrical resistance of excised rat intestinal tissue but did not significantly increase the transport of atenolol across this in vitro tissue model at the concentrations tested. At least one concentration of each aloe gel material enhanced the transport of FITC-dextran statistically significantly across Caco-2 cell monolayers. The aloe gel materials showed potential to act as drug absorption enhancing agents across intestinal epithelia. The absorption enhancement effect was dependent on the type of in vitro model and type of drug was investigated.

Chitosan-polycarbophil interpolyelectrolyte complex as a matrix former for controlled release of poorly water-soluble drugs I: in vitro evaluation.

PURPOSE: It was previously shown in our laboratories that the interpolyelectrolyte complex between chitosan and polycarbophil has promise as a matrix former to control the release of water-soluble drugs. This study further investigates the applications of this polymeric complex to produce controlled release matrices for poorly water-soluble drugs. METHODS: The swelling, erosion, and drug release performance of matrix-type tablets containing the chitosan-polycarbophil complex as matrix former was compared to those consisting of hydroxypropylmethylcellulose and a simple mixture of chitosan and polycarbophil powders. RESULTS: The chitosan-polycarbophil complex matrices showed good swelling with relatively low erosion and slower drug release compared to those prepared from other polymeric materials. They also exhibited release exponent (n) values closer to unity and therefore to zero-order release compared to the other matrices. CONCLUSIONS: The chitosan-polycarbophil complex formed matrix-type tablets that controlled the release of poorly water-soluble drugs approaching zero-order kinetics. The mechanism of drug release was mainly diffusion from swollen systems.

Effect of sinomenine on the in vitro intestinal epithelial transport of selected compounds.

Herbal products can interfere with allopathic medicinal treatment through pharmacokinetic and pharmacodynamic interactions. Although pharmacokinetic interactions that alter drug absorption may cause variable and unsatisfactory drug bioavailability, a drug absorption enhancement effect of a herb may be used to ensure sufficient absorption of poorly absorbable drugs. The effect of the hydrochloride salt of sinomenine, an alkaloid obtained from the plant Sinomenium acutum, on the transepithelial electrical resistance and transport of different compounds (including cimetidine, vitamin C, rutin, luteolin and insulin) across Caco-2 epithelial cell monolayers was investigated in this study. Sinomenine HCl induced a concentration dependent lowering effect on the transepithelial electrical resistance of Caco-2 cell monolayers, which was completely reversible. Sinomenine HCl significantly increased the transport of all the test compounds in the apical-to-basolateral direction compared with the control group and decreased the transport of cimetidine, a P-glycoprotein substrate, in the basolateral-to-apical direction. From these results it can be concluded that sinomenine HCl increases drug absorption across the intestinal epithelium by means of one or more mechanisms including a transient opening of the tight junctions (as indicated by a reduction in transepithelial electrical resistance) to allow for paracellular transport and/or inhibition of active drug efflux transport (as indicated by inhibition of basolateral-to-apical transport of cimetidine).

Intestinal drug transport enhancement by Aloe vera.

The effect of Aloe vera (L.) Burm. f. (Aloe barbadensis Miller) gel and whole leaf extract on the permeability of Caco-2 cell monolayers was determined. Solutions of gel and the whole leaf extract were applied to the cell monolayers, and the transepithelial electrical resistance was monitored for 2 hours, which was then continued for another 2 hours after removal of the test solutions to measure reversibility of the effect. The transport of insulin in the presence and absence of the A. vera gel and whole leaf extract solutions was also investigated. Both the A. vera gel and whole leaf extract were able to significantly reduce the transepithelial electrical resistance of the Caco-2 cell monolayers at concentrations above 0.5 % w/v and thereby showed the ability to open tight junctions between adjacent cells. This effect was fully reversible, as the electrical resistance of the cell monolayers returned to the original value upon removal of the test solutions. The A. vera gel and whole leaf extract solutions significantly enhanced the transport of insulin across the Caco-2 cell monolayers compared with the control. The results suggest that these plant products have a high potential to be used as absorption enhancers in novel dosage forms for drugs with poor bioavailabilities when administered orally. On the other hand, an uncontrolled increase in the bioavailability of drugs that are taken simultaneously with A. vera gel and whole leaf extract products may result in adverse effects, and the potential exists that toxic blood plasma levels may be reached.

Chitosan-polycarbophil interpolyelectrolyte complex as an excipient for bioadhesive matrix systems to control macromolecular drug delivery.

The in vitro performance of monolithic matrix systems containing the interpolyelectrolyte complex between chitosan and polycarbophil as excipient was evaluated in terms of their swelling, bioadhesive, and drug release properties. The different matrix systems showed excellent swelling properties without erosion, except for the formulation containing the highest quantity chitosan-polycarbophil complex that exhibited surface erosion in addition to swelling. All the different matrix systems exhibited significantly higher bioadhesive properties than the control group. Furthermore, they showed controlled insulin release without an initial burst release effect. However, only the matrix system that exhibited surface erosion in combination with swelling approached zero-order release.

Matrix polymeric excipients: comparing a novel interpolyelectrolyte complex with hydroxypropylmethylcellulose.

The in vitro dissolution, swelling, and erosion behavior of monolithic matrix systems containing the well-known hydrophilic polymer, hydroxypropylmethylcellulose, and a combination of chitosan and polycarbophil in the form of an interpolyelectrolyte complex were compared in this study. The two different types of matrix systems showed both a combination of swelling and erosion as the drug release mechanism. Kinetic analysis of the in vitro release profiles of water-soluble drugs from the matrix tablets illustrated that those containing the chitosan-polycarbophil complex exhibited higher mean dissolution time values and therefore slower drug release compared with the other matrix systems. The analysis also indicated that zero-order release kinetics were approached for some of the formulations containing the chitosan-polycarbophil complex, while this could not be achieved for those containing hydroxypropylmethylcellulose.

Cross-linked cationic polymer microparticles: effect of N-trimethyl chitosan chloride on the release and permeation of ibuprofen.

Microparticles made by cross-linking hydrophilic polymers, such as chitosan, have been used to modify the release rate of a loaded drug. In this study a polymer with fixed positive charges, N-trimethyl chitosan chloride (TMC), was used in combination with chitosan to formulate microparticles to investigate its effects on drug release rate and transport across intestinal epithelial cells. The microparticles were prepared by cross-linking these cationic polymer(s) using sodium citrate as the ionic cross-linker. This process was done under homogenization and ultrasonication to control the size of the particles. The addition of TMC to the chitosan microparticles resulted in an increase in particle size of the microparticles and an increase in ibuprofen release rate as compared to the microparticles containing chitosan alone. Permeation of ibuprofen across Caco-2 cell monolayers, after administration of a suspension of the microparticles to the apical side, was not significantly different for the microparticles containing TMC as compared to those consisting of chitosan alone. It was concluded that release of TMC molecules from the microparticles was probably not sufficient to interact with the intestinal epithelial cells in order to change the permeation of the released drug.