Systematic review and network meta-analysis of efficacy and safety of interventions for preventing anti-tuberculosis drug induced liver injury.

Anti-tuberculosis drug induced liver injury (Anti-TB DILI) is the most common adverse events (AEs) necessitating therapy interruption but there is no preventing regimen. This study aimed to examine the efficacy and safety of herbs/alternative medicines for preventing anti-TB DILI. Relevant articles were identified through a systematic search in 5 international databases from inception till March 2022. All randomized controlled trials (RCT) assessing the effects of herbal or alternative medicines against anti-TB DILI were included. The network meta-analysis (NMA) was used to synthesize the evidence for preventing hepatotoxicity using a random-effects model. A total of 3423 patients from 14 RCTs were included. The NMA indicated that supplementation of Turmeric plus Tinospora cordifolia (RR 0.07; 95% CI 0.02 to 0.28), and N-acetyl cysteine (NAC) (RR 0.09; 95% CI 0.01 to 0.75) significantly reduced the incidence of anti-TB DILI compared with placebo. In addition, poly herbal product significantly reduced alkaline phosphatase (ALP) (MD - 21.80; 95% CI - 33.80 to - 9.80) and total bilirubin (Tbil) compared with placebo (MD - 0.51; 95% CI - 0.76 to - 0.26). There was no statistically significant difference in the occurrence of AEs in any intervention. In conclusion, Turmeric plus Tinospora cordifolia, NAC and poly-herbal product may provide benefit for preventing anti-TB DILI in TB patients. However, these findings are based on a small number of studies. Additional studies are warranted to confirm the findings.

Sodium caseinate-magnesium aluminum silicate nanocomposite films for modified-release tablets.

The aim of this study was to investigate the effect of clay, magnesium aluminum silicate (MAS), on the properties of sodium caseinate (SC) dispersions and films. Moreover, the SC-MAS dispersions were evaluated for film coating of modified-release tablets. The results showed that MAS addition led to particle flocculation and viscosity synergism in the SC-MAS dispersions. Exfoliated or intercalated nanocomposites of the SC-MAS films could be formed because of the molecular interaction of both components via hydrogen bonding. The puncture strength and elongation of the dry SC films decreased with increasing MAS ratios. However, MAS added enhanced the puncture strength of the wet films and reduced drug permeability and diffusivity across the films in acidic medium because of lower water uptake and denser matrix structure of the films. The SC-MAS dispersions showed strong potential for use as a film coating material with few defects in the coated acetaminophen (ACT) tablets. The ACT release of the coated tablets in acidic medium was modified by varying the MAS ratios and film coating levels. In addition, the SC-MAS coated tablets possessed sustained-release behavior for the drug under simulated gastrointestinal conditions. This finding indicates that the SC-MAS nanocomposite films can be applied as a tablet coating material to modify drug release.

Modification of gellan gum films by halloysite: physicochemical evaluation and drug permeation properties.

The aim of this study was to determine the potential of gellan gum (GG) and halloysite (HS) dispersions at different mixing ratios and to investigate the potential of GG-HS dispersions in film formation. To this end, the dispersions and films were characterized. The dispersions formed films with large particles ranging from 3 to 4 µm in size, with a zeta potential of ∼-35 mV. The GG-HS films were fabricated using a solvent-casting technique, which generated films with a white opaque appearance and rough surface. The GG-HS films were formed via hydrogen bonding and electrostatic interactions at the inner cavity and outer surface, as confirmed by ATR-FTIR spectroscopy and X-ray diffractometry. The %water uptake and erosion of the GG-HS film decreased with increasing HS content, whereas both puncture strength and elongation were increased in the GG-HS ratios of 1:0.4 and 1:1.2. Moreover, addition of HS into the GG films could possibly decrease drug permeability coefficient when using higher HS ratio in acidic and neutral media. These results suggested that HS modifies the characteristics of the GG used to coat modified-release tablets.

Chitosan-gum arabic polyelectrolyte complex films: physicochemical, mechanical and mucoadhesive properties.

By blending chitosan (CS) and gum arabic (GA), a powerful biomaterial complex might be obtained due to the unique properties of CS and the low viscosity and good emulsifying properties of GA. The objectives of this study were to prepare and examine the properties of dispersions and films of CS and GA as a function of the mixing weight ratio, pH value and molecular weight of CS. The dispersions were characterized by turbidity, zeta potential and cytotoxicity and then the dispersions were cast into films. Physicochemical properties of the film were performed. CS-GA dispersions exhibited higher turbidity and a lower zeta potential with an increase in the GA ratio. Continuous films of the CS-GA could be formed at all ratios. CS and GA could molecularly interact via electrostatic forces and intermolecular hydrogen bonding. The CS-GA (1:0.5) films exhibited relatively low water uptake, erosion, water vapor permeability and puncture strength compared to the CS films. Furthermore, the CS-GA films demonstrated good mucoadhesive properties, allowing for adhesion to the mucosal membrane. Based on these results, it could be advantageous to use CS-GA films as film formers for the formulation of coatings and drug delivery systems.

Combining two technologies: multifunctional polymers and self-nanoemulsifying drug delivery system (SNEDDS) for oral insulin administration.

The aim of the study is to develop a self-nanoemulsifying drug delivery system (SNEDDS) based on thiolated chitosan for oral insulin administration. The preparations were characterized by particle size, entrapment efficiency, stability and drug release. Serum insulin concentrations were determined after oral administration of all formulations. Insulin SNEDDS formulation was served as control. The optimized SNEDDS consists of 65% (w/w) miglyol 840, 25% (w/w) cremophor EL, 10% (w/w) co-solvents (a mixture of DMSO and glycerol). The formulations in the presence or absence of insulin (5mg/mL) were spherical with the size range between 80 and 160 nm. Entrapment efficiency of insulin increased significantly when the thiolated chitosan was employed (95.14±2.96%), in comparison to the insulin SNEDDS (80.38±1.22%). After 30 min, the in vitro release profile of insulin from the nanoemulsions was markedly increased compared to the control. In vivo results showed that insulin/thiolated chitosan SNEDDS displayed a significant increase in serum insulin (p-value=0.02) compared to oral insulin solution. A new strategy to combine SNEDDS and thiolated chitosan described in the study would therefore be a promising and innovative approach to improve oral bioavailability of insulin.

S-protected thiolated chitosan: synthesis and in vitro characterization.

Purpose of the present study was the generation and evaluation of novel thiolated chitosans, so-named S-protected thiolated chitosans as mucosal drug delivery systems. Stability of all conjugates concerning swelling and disintegration behavior as well as drug release was examined. Mucoadhesive properties were evaluated in vitro on intestinal mucosa. Different thiolated chitosans were generated displaying increasing amounts of attached free thiol groups on the polymer, whereby more than 50% of these thiol groups were linked with 6-mercaptonicotinamide. Based on the implementation of this hydrophobic residue, the swelling behavior was 2-fold decreased, whereas stability was essentially improved. Their mucoadhesive properties were 2- and 14-fold increased compared to corresponding thiolated and unmodified chitosans, respectively. Release studies out of matrix tablets comprising the novel conjugates revealed a controlled release of a model peptide. Accordingly, S-protected thiomers represent a promising type of mucoadhesive polymers for the development of various mucosal drug delivery systems.

In situ gelling properties of anionic thiomers.

The aim of this study was to investigate in situ crosslinking systems of anionic thiolated polymers. In order to accelerate the increase in dynamic viscosity of thiolated polymers (thiomers), they were combined with hydrogen peroxide, carbamide peroxide and ammonium persulfate. Thiomers (pectin-cysteine (Pec-Cys), sodium carboxymethylcellulose-cysteine (NaCMC-Cys) and poly(acrylic acid)-cysteine (PAA-Cys)) were synthesized via amide bond formation between the carboxylic acid group of polymers and the primary amino group of l-cysteine. The rheological properties of 1% (m/v) thiomer solutions with oxidizing agents were compared by oscillatory measurements over time (120 min). Pec-Cys and NaCMC-Cys with hydrogen and carbamide peroxide showed a sol-gel phase transition within a few minutes and scored up to 13,000-fold increase in dynamic viscosity. Furthermore, only thiomers exhibiting a polysaccharide backbone (Pec-Cys and NaCMC-Cys) showed a significant increase in viscosity (p < 0.05). In contrast, measurements of carbohydrate thiomers in combination with ammonium persulfate showed an initial increase in viscosity. Afterwards, a decrease in viscosity was observed likely caused by chain scission. According to these results, carbohydrate thiomer/oxidizing agent systems might be useful for various pharmaceutical applications such as for in situ gelling liquid/semisolid formulations or in tissue engineering.

HEC-cysteamine conjugates: influence of degree of thiolation on efflux pump inhibitory and permeation enhancing properties.

Within the present study hydroxyethyl cellulose-cysteamine conjugates are investigated regarding biocompatibility, in situ gelling, permeation enhancing and efflux pump inhibitory properties. For this purpose, a series of concentrations of sodium periodate was prepared to oxidize HEC leading to ring opening of glucose subunits. The resulting polymers showing varying degrees of oxidation (DO) were then conjugated with cysteamine stabilized via reductive amination. Consequently, HEC-cysteamine conjugates with increasing degree in thiolation were obtained. Since the conjugates are positively charged, potency of cytotoxicity was tested by resazurin assay. In situ gelling properties of the conjugates were studied to investigate change of their viscosity due to inter- and/or intramolecular crosslinking via disulfide bonds. The influence of the presence of the conjugates on transport of rhodamine 123 and fluoresceinisothiocyanate-dextran 4 (FD4) representing model compounds for P-glycoprotein (P-gp) inhibition and permeation enhancing studies, respectively, across Caco-2 cell monolayers was determined. The conjugates showed a degree of thiolation in the range of 316-2158 µmol/g. Within 30 min, dynamic viscosity of the conjugate with the lowest degree of thiolation 0.5% (m/v) increased up to 300-fold. The conjugates showed a degree of thiolation-dependent increase in cytotoxicity but they all were found comparatively low cytotoxic. The addition of the conjugate with thiol group content of 1670 µmol/g resulted in the highest improvement in the transport of both rhodamine 123 and FD4 as compared to buffer control. Accordingly, the degree of thiolation strongly influences the properties of the conjugates and the modulation of the degree of thiolation could be exploited for development of various drug delivery systems.

Synergistic effects of conjugating cell penetrating peptides and thiomers on non-viral transfection efficiency.

Nanoparticles generated by complex coacervation of plasmid DNA (pDNA) and modified chitosans namely chitosan-thioglycolic acid (TGA) conjugate and chitosan-HIV-1 Tat peptide conjugate were evaluated as gene delivery systems. In order to optimize transfection efficiency, chitosan-HIV-1 Tat peptide conjugate was combined with chitosan-TGA before its complexation with pDNA. Particle size and zeta potential measurements were performed to characterize the generated nanoparticles. The nanoparticles transfection efficiencies were assessed by exploitation of the green fluorescent protein (GFP) reporter gene. HEK293 cells were incubated for 24 h with the nanoparticles and the GFP positive cells were observed by fluorescence microscopy. The nanoparticles in the size range of 200-300 nm could transfect HEK293 cells as a model cell line with different transfection efficiencies. Unlike chitosan-TGA, chitosan-HIV-1 Tat peptide led to increased zeta potential of nanoparticles as compared to unmodified chitosan. The transfection efficiency of the nanoparticles generated by combination of chitosan-HIV-1 Tat peptide with chitosan-TGA was comparatively higher than that of the nanoparticles generated by either chitosan-TGA or the combination of chitosan-HIV-1 Tat peptide with unmodified chitosan. After 72 h of incubation, the combination of chitosan-HIV-1 Tat peptide with chitosan-TGA was found to be 7.12- and 67.37 times more efficient than unmodified chitosan and pDNA alone, respectively and showed a synergistic effect in transfection of pDNA into the cells. Moreover, none of the nanoparticles showed any severe cytotoxicity. Accordingly, this strategy might result in a potent carrier for gene delivery.

Thiolated chitosans: influence of various sulfhydryl ligands on permeation-enhancing and P-gp inhibitory properties.

PURPOSE: The influence of various sulfhydryl ligands on permeation-enhancing and P-glycoprotein (P-gp) inhibitory properties of the six established thiolated chitosan conjugates was investigated using Rhodamine-123 (Rho-123) and fluorescein isothiocyanate-dextran 4 (FD4) as model compounds. METHODS: Permeation of these compounds was tested on freshly excised rat intestine in Ussing-type chambers. Apparent permeability coefficients (Papp) were calculated and compared to values obtained from the buffer only control. RESULTS: The lyophilized polymers had a thiol group content in the range of 230-520 µmol/g. Results of this study led to the following rank order in permeation enhancement: chitosan-6-mercaptonicotinic acid (chitosan-6MNA) > chitosan-cysteine (chitosan-Cys) > chitosan-glutathione (chitosan-GSH) > chitosan-4-thiobutylamidine (chitosan-TBA) > chitosan-thioglycolic acid (chitosan-TGA) > chitosan-N-acetyl cysteine (chitosan-NAC). In P-gp inhibition studies, 0.5% (m/v) chitosan-NAC showed the highest inhibitory effect on P-gp, where the Papp was determined to be 3.78-fold increased compared with the buffer control. Among these thiolated chitosans, chitosan-NAC and chitosan-6MNA are the most effective polymers being responsible for P-gp inhibition and permeation enhancement, respectively. CONCLUSION: These thiolated chitosans would therefore be advantageous tools for enhancing the noninvasive bioavailability of active pharmaceutical ingredients.

Thiomers: Inhibition of cytochrome P450 activity.

The aim of the present study was to investigate the potential of different thiolated polymers (thiomers) on the catalytic activity of CYP450s on one hand and to explore new inhibitors for CYP activity on the other hand. Several thiolated polymers including poly(acrylic acid)-cysteine (PAA-cysteine), chitosan-thioglycolic acid (chitosan-TGA), and thiolated PEG-g-PEI copolymer along with brij 35, myrj 52 and the well-established CYPP450 inhibitor verapamil were screened for their CYP3A4 and CYP2A6 inhibitory activity, and their IC(50) values were determined. Both enzyme inhibition assays were performed in 96-well microtiter plates. 7-Benzyloxy-4-(trifluoromethyl)-coumarin (BFC) and 7-hydroxycoumarin (7-HC) were used as fluorescent substrates in order to determine CYP3A4 and CYP2A6 catalytic activity, respectively. All investigated compounds inhibited CYP3A4 as well as CYP2A6 activity. All tested (thiolated) polymers were found to be more potent inhibitors of CYP3A4 than of CYP2A6 catalytic activity. Apart from verapamil that is a known CYP3A4 inhibitor, brij 35 and myrj 52 were explored as potent inhibitors of CYP3A4 and CYP2A6 catalytic activity. Among the tested polymers, the rank order for CYP3A4 inhibition was PAA-cysteine (100 kDa)>brij 35>thiolated PEG-g-PEI copolymer (16 kDa)>myrj 52>PAA (100 kDa)>PAA-cysteine (450 kDa)>verapamil>PAA (450 kDa)>chitosan-TGA (150 kDa)>chitosan (150 kDa). On the other hand, the rank order of CYP2A6 inhibition was brij 35>PAA-cysteine (100kDa)>chitosan-TGA (150 kDa)>PAA (100 kDa)>thiolated PEG-g-PEI copolymer (16 kDa)>PAA-cysteine (450 kDa)>chitosan (150 kDa)>verapamil>PAA (450 kDa)>myrj 52. Thus, this study suggests that (thiolated) polymers display a promising potential to inhibit cytochrome P450s activity and might turn out to be potentially valuable tools for improving the oral bioavailability of actively secreted compounds by avoiding intestinal metabolism.

Design and synthesis of a novel cationic thiolated polymer.

The purpose of this study was to design and characterize a novel cationic thiolated polymer. In this regard a hydroxyethylcellulose-cysteamine conjugate (HEC-cysteamine) was synthesized. Oxidative ring opening with periodate and reductive amination with cysteamine were performed in order to immobilize free thiol groups to HEC. The resulting HEC-cysteamine displayed 2035 ± 162 µmol immobilized free thiol groups and 185 ± 64 µmol disulfide bonds per gram of polymer being soluble in both acidic and basic conditions. Unlike the unmodified HEC, in case of HEC-cysteamine, a three-fold increase in the viscosity was observed when equal volumes of the polymer were mixed with mucin solution. Tablets based on HEC-cysteamine remained attached on freshly excised porcine mucosa for 8 0h and displayed increased disintegration time of 2h. Swelling behavior of HEC-cysteamine tablets in 0.1M phosphate buffer pH 6.8 indicated swelling ratio of 19 within 8h. In contrast, tablets comprising unmodified HEC detached from the mucosa within few seconds and immediately disintegrated. In addition, they did not exhibit swelling behavior. The transport of rhodamine 123 across freshly excised rat intestine enhanced by a value of approximately 1.6-fold (p-value = 0.0024) in the presence of 0.5% (m/v) HEC-cysteamine as compared to buffer control. Result from cytotoxicity test of HEC-cysteamine applied to Caco-2 cells in concentration of 0.5% (m/v) revealed 82.4 ± 4.60% cell viability. According to these results, HEC-cysteamine seems to be a promising polymer for various pharmaceutical applications especially for intestinal drug delivery.

Distribution of thiolated mucoadhesive nanoparticles on intestinal mucosa.

It was the aim of the present study to evaluate and compare the distribution of thiolated mucoadhesive anionic poly(acrylic acid) (PAA) and cationic chitosan (CS) nanoparticles on intestinal mucosa. Modifications of these polymers were achieved by conjugation with cysteine (PAA-Cys) and 2-iminothiolane (CS-TBA). Nanoparticles (NP) were prepared by ionic gelation and labelled with the strong hydrophilic fluorescent dye Alexa Fluor 488 (AF 488) and hydrophobic fluorescein diacetate (FDA). Unmodified and modified CS and PAA NP were examined in vitro in terms of their mucoadhesive and mucus penetrating properties on the mucosa of rat small intestine. To investigate the transport of NP across the mucus layer, their diffusion behaviour through natural porcine intestinal mucus was studied through a new diffusion method developed by our group. Lyophilised particles displayed 526 µmol/g (CS) and 513 µmol/g (PAA) of free thiol groups and a zeta potential of 20 mV (CS) and -14 mV for PAA NP. Nanoparticle distribution on rat intestine suggested that mucoadhesion of thiolated NP is higher than the diffusion into the intestinal mucosa. Modified particles displayed more than a 6-fold increase in mucoadhesion compared to unmodified ones. The rank order with regard to mucoadhesion of all particles was: CS-TBA>PAA-Cys>CS>PAA, whereas CS-TBA showed 2-fold higher mucoadhesive properties compared to PAA-Cys NP. Diffusion through intestinal mucus was much higher for unmodified than for thiolated as well as for anionic compared to cationic particles. Overall, it was shown that thiolated particles of both anionic and cationic polymers have improved mucoadhesive properties and could be promising carriers for mucosal drug delivery.

Thiolated hydroxyethylcellulose: synthesis and in vitro evaluation.

In recent years, thiomers have received considerable interest due to advantageous characteristics, such as improved mucoadhesive and permeation enhancing properties. Thiolated polymers, however, are characterized by an ionic charge which represents for various applications a great limitation. The aim of this study was therefore to synthesize a novel thiolated polymer not exhibiting ionizable groups. Hydroxyethylcellulose (HEC) was chosen as polymer backbone. The chemical modification was achieved by the replacement of hydroxyl groups on the carbohydrate structure with thiol moieties, using thiourea as thiolating reagent. The resulting thiolated hydroxyethylcellulose (HEC-SH) was characterized in vitro regarding its gelling properties, swelling behaviour, mucoadhesion on freshly excised porcine intestinal mucosa and permeation enhancing effect across rat intestinal mucosa. The new thiomer displayed up to 131.58 ± 11.17 µmol thiol groups per gram polymer, which are responsible for the observed in situ gelling capacity. The swelling behaviour and the mucoadhesive properties of tablets based on HEC-SH were 1.5-fold and 4-fold improved compared with unmodified HEC, respectively. The permeation enhancing effect of 0.5% (m/v) HEC-SH on rhodamine 123 (Rho-123) transport was 1.9-fold improved compared with buffer only. According to these results, HEC-SH seems to represent a promising tool for the development of in situ gelling, mucoadhesive delivery systems with permeation enhancing properties.

The impact of vehicles on the mucoadhesive properties of orally administrated nanoparticles: a case study with chitosan-4-thiobutylamidine conjugate.

The aim of this study was to evaluate the impact of various vehicles on mucoadhesive properties of thiolated chitosan nanoparticles both in vitro and in vivo. Nanoparticles (NPs) were prepared by in situ gelation technique followed by labeling with fluorescein diacetate. Comparative studies on mucoadhesion were done with these thiolated chitosan NPs and unmodified chitosan NPs (control). The obtained nanoparticles displayed a mean diameter of 164.2 ± 6.9 nm and a zeta potential of 21.5 ± 5 mV. In an in vitro adhesion study, unhydrated thiolated NPs adhered strongly to freshly excised porcine small intestine, which was more than threefold increase compared to the control. In contrast, in the presence of various vehicles (PEG 300, miglyol 840, PEG 6000, cremophor EL, and caprylic triglyceride), the mucoadhesive properties of thiolated NPs were comparatively weak. Thiolated NPs suspended in caprylic triglyceride, for example, had a percent mucoadhesion of 22.50 ± 5.35% on the mucosa. Furthermore, results from in vivo mucoadhesion studies revealed that the dry form of nanoparticles exhibits the strongest mucoadhesion, followed by nanoparticles suspended in PEG 300, miglyol, and 100 mM phosphate buffer, in that order. Three hours after administration, the gastrointestinal residence time of the dry form of thiolated NPs was up to 3.6-fold prolonged. These findings should contribute to the design of highly effective oral mucoadhesive nanoparticulate drug delivery systems.

In situ gelling properties of chitosan-thioglycolic acid conjugate in the presence of oxidizing agents.

The rheological behaviour of chitosan-thioglycolic acid conjugate (chitosan-TGA) in the presence of four oxidizing agents was investigated. Chitosan-TGA was synthesized via amide bond formation between the primary amino group of chitosan and the carboxylic acid group of thioglycolic acid. The sol-gel phase transition of the polymer was determined by rheological measurements. Moreover, cytotoxicity of the gel in combination with each oxidizing agent was evaluated utilizing LDH and MTT assay. The modified chitosan displayed 1053+/-44 micromol/g thiol groups. Results of rheological studies showed that 1% (m/v) chitosan-TGA without any oxidizing agents became gel within 40 min. In contrast, when the oxidizing agents hydrogen peroxide, sodium periodate, ammonium persulfate and sodium hypochlorite were added, respectively, gelation took place within a few minutes. Within 20 min, hydrogen peroxide having been added in a final concentration of 25.2 nmol/L increased dynamic viscosity of 1% (m/v) chitosan-TGA up to 16,500-fold. This can be explained by the formation of inter- and/or intramolecular disulfide bonds which were indirectly verified via the decrease in thiol groups. Additionally, evidence of an increase in cross-linking of thiolated chitosan as a function of time was provided by frequency sweep measurements. Furthermore, viability of Caco-2 cells having been incubated with chitosan-TGA/oxidizing agent systems assessed by MTT assay was 70-85% and the percentage of LDH release was only in case of the chitosan-TGA/ammonium persulfate system significantly (p<0.05) raising compared to the negative control. According to these results, chitosan-TGA/oxidizing agent combinations might be a promising novel in situ gelling system for various pharmaceutical applications such as a controlled drug release carrier or for tissue engineering.