Overestimation of rifampicin during colorimetric analysis of anti-tuberculosis products containing isoniazid due to formation of isonicotinyl hydrazone

State of the Art on Developments of (Bio)Sensors and Analytical Methods for Rifamycin Antibiotics Determination

This review summarizes the literature data reported from 2000 up to the present on the development of various electrochemical (voltammetric, amperometric, potentiometric and photoelectrochemical), optical (UV-Vis and IR) and luminescence (chemiluminescence and fluorescence) methods and the corresponding sensors for rifamycin antibiotics analysis. The discussion is focused mainly on the foremost compound of this class of macrocyclic drugs, namely rifampicin (RIF), which is a first-line antituberculosis agent derived from rifampicin SV (RSV). RIF and RSV also have excellent therapeutic action in the treatment of other bacterial infectious diseases. Due to the side-effects (e.g., prevalence of drug-resistant bacteria, hepatotoxicity) of long-term RIF intake, drug monitoring in patients is of real importance in establishing the optimum RIF dose, and therefore, reliable, rapid and simple methods of analysis are required. Based on the studies published on this topic in the last two decades, the sensing principles, some examples of sensors preparation procedures, as well as the performance characteristics (linear range, limits of detection and quantification) of analytical methods for RIF determination, are compared and correlated, critically emphasizing their benefits and limitations. Examples of spectrometric and electrochemical investigations of RIF interaction with biologically important molecules are also presented.

Monomer Release from Dental Resins: The Current Status on Study Setup, Detection and Quantification for In Vitro Testing

Improvements in mechanical properties and a shift of focus towards esthetic dentistry led to the application of dental resins in various areas of dentistry. However, dental resins are not inert in the oral environment and may release monomers and other substances such as Bisphenol-A (BPA) due to incomplete polymerization and intraoral degradation. Current research shows that various monomers present cytotoxic, genotoxic, proinflammatory, and even mutagenic effects. Of these eluting substances, the elution of BPA in the oral environment is of particular interest due to its role as an endocrine disruptor. For this reason, the release of residual monomers and especially BPA from dental resins has been a cause for public concern. The assessment of patient exposure and potential health risks of dental monomers require a reliable experimental and analytical setup. However, the heterogeneous study design applied in current research hinders biocompatibility testing by impeding comparative analysis of different studies and transfer to the clinical situation. Therefore, this review aims to provide information on each step of a robust experimental and analytical in vitro setup that allows the collection of clinically relevant data and future meta-analytical evaluations.

A comparative in vitro study on monomer release from bisphenol A-free and conventional temporary crown and bridge materials

This study aimed to investigate the release of common monomers from two conventional and two bisphenol A (BPA)-free temporary crown and bridge materials. Cylindrical samples of all materials were prepared (N = 90; five samples for each material and cycle of analysis). All samples were immersed in high-performance liquid chromatography (HPLC)-grade water and incubated for 1 h, 12 h, 24 h, and 7 days in an incubation shaker at 37°C and 112 rpm. Extraction was performed in accordance with ISO 10993-12. Eluted monomers were detected and quantified by HPLC coupled with ultraviolet-visible spectroscopy and mass spectrometry (HPLC-UV/Vis-MS). Analysis of BPA was performed by HPLC coupled with ultraviolet-visible spectroscopy (HPLC-UV/Vis) and positive results were verified by HPLC-tandem mass spectrometry (HPLC-MS/MS). Neither bisphenol A-glycidyl methacrylate (Bis-GMA) nor BPA was quantifiable in any of the crown and bridge samples investigated in the present study. However, all samples contained triethylene glycol dimethacrylate (TEGDMA) and/or urethane dimethacrylate (UDMA) after 24 h of incubation. Statistical analysis showed that significantly more UDMA was released from the BPA-free materials than from the conventional materials. All concentrations of UDMA measured were below the effective cytotoxic concentrations previously reported. However, for a few materials, especially BPA-free temporary crown and bridge materials, the levels of UDMA were above previously reported potentially harmful concentrations for local cells. As BPA-free materials were introduced as being more biocompatible than materials containing BPA, substitution of Bis-GMA with UDMA should be further investigated.

Sugar-Grafted Cyclodextrin Nanocarrier as a "Trojan Horse" for Potentiating Antibiotic Activity

PURPOSE

The use of "Trojan Horse" nanocarriers for antibiotics to enhance the activity of antibiotics against susceptible and resistant bacteria is investigated.

METHODS

Antibiotic carriers (CD-MAN and CD-GLU) are prepared from β-cyclodextrin grafted with sugar molecules (D-mannose and D-glucose, respectively) via azide-alkyne click reaction. The sugar molecules serve as a chemoattractant enticing the bacteria to take in higher amounts of the antibiotic, resulting in rapid killing of the bacteria.

RESULTS

Three types of hydrophobic antibiotics, erythromycin, rifampicin and ciprofloxacin, are used as model drugs and loaded into the carriers. The minimum inhibitory concentration of the antibiotics in the CD-MAN-antibiotic and CD-GLU-antibiotic complexes for Gram-negative Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii strains, and a number of Gram-positive Staphylococcus aureus strains, including the methicillin-resistant strains (MRSA), are reduced by a factor ranging from 3 to >100. The CD-MAN-antibiotic complex is also able to prolong the stability of the loaded antibiotic and inhibit development of intrinsic antibiotic resistance in the bacteria.

CONCLUSIONS

These non-cytotoxic sugar-modfied nanocarriers can potentiate the activity of existing antibiotics, especially against multidrug-resistant bacteria, which is highly advantageous in view of the paucity of new antibiotics in the pipeline.

Halide ion-driven self-assembly of Zn(ii) compounds derived from an asymmetrical hydrazone building block: a combined experimental and theoretical study

Self-assembly of Zn(ii) compounds is influenced by a counter ion and non-covalent interactions.

Using rifapentine - hen egg lipoprotein conjugate as macrophage-targeted drug delivery carrier against intracellular Staphylococcus aureus

CONTEXT

Hen egg low-density lipoprotein (heLDL), which is present in large quantities in egg yolk, share a high identity with human apolipoprotein B-100 precursor.

OBJECTIVE

This study investigated the use of heLDL as a macrophage-targeted drug delivery carrier against intracellular Staphylococcus aureus.

METHODS

Rifapentine (RPT) was incorporated into heLDL (RPT-heLDL). Staphylococcus aureus ATCC 29740 and human U937 macrophage were used as intracellular infection models.

RESULTS AND CONCLUSION

The loading efficiency of RPT into the heLDL was 66.10 ± 2.28 μg RPT/mg heLDL. Fluorescence microscopy and oil red O staining results indicated RPT-heLDL can be taken up by U937 macrophages. The cell viability (MTT assay) was increased when the concentration of heLDL was <150 μg/mL. Unloaded heLDL (100 μg/mL) can inhibit the growth of intracellular S. aureus compared with the untreated control group after 18 h incubation. RPT-heLDL (6.6 μg/mL RPT, 100 μg/mL heLDL) eliminated 94% of intracellular S. aureus, whereas the corresponding dose of free RPT (6.6 μg/mL) induced an 87% reduction. The in vitro results of the current study indicated that heLDL might be used as a suitable drug carrier for targeting human macrophages.

LC-MS/TOF and UHPLC-MS/MS study of in vivo fate of rifamycin isonicotinyl hydrazone formed on oral co-administration of rifampicin and isoniazid

The formation and fate of 3-formylrifamycin isonicotinyl hydrazone (HYD) was investigated following oral co-administration of rifampicin (RIF) and isoniazid (INH) in Sprague-Dawley (SD) rats (n=5) using advanced analytical modalities. The study was carried out with 20 and 5mg/kg doses of RIF and INH, respectively. The plasma, urine and faeces samples were collected at different time points up to 48h, which were qualitatively and quantitatively evaluated for the presence of HYD after proper sample preparation. For the same, initially liquid chromatography-mass spectrometry/time-of-flight (LC-MS/TOF) method was developed in electrospray ionization (ESI) positive mode, wherein separation was achieved on a C18 column (4.6mmx250mm, 5microm), using a volatile mobile phase in a gradient mode. The presence of HYD was confirmed by accurate mass study, spiking with the standard and UV-visible spectra matching. For quantitative evaluation of HYD, a selective and sensitive ultra high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed for all the three matrices. In this case, elution of HYD was achieved on a small C18 column (4.6mmx50mm, 1.8microm) using a short gradient method. The quantitation was done by selective reaction monitoring (SRM) in ESI positive mode. The validation parameters like linearity, accuracy, precision, selectivity, matrix effect, recovery and stability were assessed as per regulatory guidelines. The calibration range was established between 1 and 200ng/ml, with r(2)>0.99 in all the cases. The back calculated values for three quality control (QC) samples, and at lower limit of quantitation (LLOQ) were within 15 and 20%, respectively, of the nominal values. Similarly, the intra- and inter-day precisions were found within 15% at the four tested levels. The HYD was found to be stable for the duration of sample preparation and analysis in the controlled experimental conditions. The analysis of in vivo samples showed a significant extent of HYD in faeces, however, the interaction product was not found in plasma and urine. To verify the results, 5mg/kg oral dose of HYD standard was given to rats separately, and its presence was studied in all the three matrices. Further, in vitro plasma stability of HYD was also carried out to explain its absence in plasma and urine, which showed approximately 55% disappearance of HYD in 2h.

Formulation and Statistical Optimization of a Novel Crosslinked Polymeric Anti‐Tuberculosis Drug Delivery System

The crux of this research was the pragmatic investigation into the formulation of a reconstitutable multiparticulate anti-tuberculosis drug delivery system for facilitated administration for the attainment of segregated gastrointestinal (GI) delivery of rifampicin (RIF) and isoniazid (INH) in order to address issues of unacceptable RIF bioavailability on coadministration with INH. Ionotropically crosslinked polymeric enterospheres for delivery of INH to the small intestine were developed via a response surface methodology for the design and optimization of the formulation and processing variables. A 3(4) Box-Behnken statistical design was constructed. The concentration of zinc sulfate salting-out and crosslinking electrolyte, the crosslinking reaction time, the drying temperature (DT), and the concentration of triethyl citrate plasticizer were varied for determination of their effect on the molar amount of zinc (n(Zn)) incorporated in the crosslinked enterosphere, drug entrapment efficiency (DEE), and mean dissolution time (MDT) at t(2h) in acidic media (0.1 M HCl). Complexometric determination of zinc cations (Zn(2+)) revealed that 23.70-287.89 mol of Zn(2+) per mole of polymer were implicated in crosslink formation. DEE of 27.92% to 99.77% were obtained. Drug release at t(2h) ranged from 1.67% to 73.04%. The salting-out and crosslinking agent significantly affected n(Zn) (p = 0.034) and the DEE (p = 0.000), as did the concentration of plasticizer employed (p = 0.000 and 0.002, respectively). High DTs (>42.5 degrees C) also significantly improved DEE (p = 0.029). ZnSO(4) had a significant effect on the MDT (p = 0.000). A dry dispersible multiparticulate system incorporating the optimally designed INH-loaded enterospheres and RIF was developed. Bivariate regression analysis of UV spectrophotometric absorbance data allowed in vitro resolution of RIF and INH release at simulated gastric pH.

Tuberculosis chemotherapy: current drug delivery approaches

Tuberculosis is a leading killer of young adults worldwide and the global scourge of multi-drug resistant tuberculosis is reaching epidemic proportions. It is endemic in most developing countries and resurgent in developed and developing countries with high rates of human immunodeficiency virus infection. This article reviews the current situation in terms of drug delivery approaches for tuberculosis chemotherapy. A number of novel implant-, microparticulate-, and various other carrier-based drug delivery systems incorporating the principal anti-tuberculosis agents have been fabricated that either target the site of tuberculosis infection or reduce the dosing frequency with the aim of improving patient outcomes. These developments in drug delivery represent attractive options with significant merit, however, there is a requisite to manufacture an oral system, which directly addresses issues of unacceptable rifampicin bioavailability in fixed-dose combinations. This is fostered by the need to deliver medications to patients more efficiently and with fewer side effects, especially in developing countries. The fabrication of a polymeric once-daily oral multiparticulate fixed-dose combination of the principal anti-tuberculosis drugs, which attains segregated delivery of rifampicin and isoniazid for improved rifampicin bioavailability, could be a step in the right direction in addressing issues of treatment failure due to patient non-compliance.