Development of Competitive ELISA and CLEIA for Quantitative Analysis of Polymyxin B

Determination of polymyxin B in human plasma and epithelial lining fluid using LC-MS/MS and its clinical application in therapeutic drug monitoring

Polymyxin B (PB) is currently one of the last resort treatment options against carbapenem-resistant gram-negative bacterial pathogens. Pharmacokinetics/pharmacodynamics (PK/PD) guided therapeutic drug monitoring (TDM) of antibiotics is critical for optimizing dosage regimens to maximize efficacy, minimize toxicity, and delay the emergence of resistance. Currently, methods for determining PB in human plasma and epithelial lining fluid (ELF) are limited. In this study, we developed and validated a simple method for PB determination in human plasma and ELF using LC-MS/MS. Protein precipitation of the sample was conducted with 0.1% formic acid-acetonitrile. Polymyxin B1 and B2 were separated on a C₁₈ column and detected within 4 min by the mass spectrometer in the positive mode coupled with multiple reaction monitoring. The calibration curve range was 0.156-10.0 and 0.0156-1.00 μg/mL in the plasma for polymyxin B1 and B2, respectively, and was 0.0625-2.00 and 0.00625-0.200 μg/mL for polymyxin B1 and B2, respectively in bronchoalveolar lavage fluid. The accuracy of the intra- and inter-assay studies ranged from 80.6% to 114.9%, and the coefficients of variation for intra- and inter-day assays were less than 14.8%. Among a considerable number of patients, the average steady-state plasma concentration of PB was suboptimal. Moreover, the exposure to PB in patients with acute kidney injury (AKI) was considerably higher than that in patients without AKI. Meanwhile, a higher concentration of PB in ELF could be achieved than that in plasma after PB nebulization treatment. The established method was proven to be rapid, simple, and suitable for TDM of PB and PK/PD studies in human plasma and ELF.

Development of Indirect Competitive ELISA and Colloidal Gold Immunochromatographic Strip for Endosulfan Detection Based on a Monoclonal Antibody

Endosulfan, as an effective broad-spectrum insecticide, has been banned in agricultural areas because of the potential harmful effects on human health. This study aimed to develop an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and colloidal gold immunochromatographic (ICA) strip based on a prepared monoclonal antibody (mAb) for quantitative and qualitative detection of endosulfan. A new mAb with high sensitivity and affinity was designed and screened. The ic-ELISA showed a 50% inhibition concentration (IC₅₀) value of 5.16 ng/mL for endosulfan. Under optimum conditions, the limit of detection (LOD) was determined to be 1.14 ng/mL. The average recoveries of endosulfan in spiked pear and apple samples ranged from 91.48-113.45% and 92.39-106.12% with an average coefficient of variation (CV) of less than 7%, respectively. The analysis of colloidal gold ICA strip could be completed within 15 min by naked eye and the visual limit of detection (vLOD) was both 40 ng/mL in pear and apple samples. In conclusion, both developed immunological methods were suitable and reliable for the on-site detection of endosulfan in real samples at trace levels.

Ratiometric detection of polymyxin B based on the disaggregation of pyrenyl nanoassemblies in 100% aqueous media

Polymyxin B (PMB) was an antibiotic with highly effective antibacterial effect but narrow safety interval, and its residues in food had attracted widespread attention. It was important to develop an accurate method for the rapid detection of PMB in animal foods. In this work, we had established a ratiometric sensing system based on the formation of supramolecular assemblies of pyrenyl probes, which were driven by the synergy of noncovalent forces such as multiple-electrostatic and π-π stacking interactions. Compared with the traditional fluorescence detection based on the single wavelength change, the present approach showing two-wavelength fluorescence response could reduce the interference of other factors making the experimental results more accurate. The sensor exhibited high sensitivity and selectivity with a low detection limit (28.3 nM). This method could be used to realize visual detection and had a visual detection limit of 1 μM. As we had learned yet, this was the first ratiometric sensor for PMB detection in aqueous solution. We believed all our preliminary would not only provide a complementary strategy for the detection of PMB, but also develop some new ideas for the construction of sensors for rapid antibiotic detection.

Salvage Parenteral Antibiotics for Multidrug-Resistant (MDR) Gram-Negative Bacteria; A Fluorescamine-Based Technique for Ultrasensitive Spectrofluorimetric Measurement of Polymyxins; Human Plasma Application

Polymyxins (PMS), namely Colistin (CS) and Polymyxin B (Poly B), are antimicrobial drugs that recently used to treat multi-resistant gram-negative bacteria infections and their resurgence owing to a lack of new antibiotics. A speedy, simple, and ultrasensitive spectrofluorimetric screening of PMS in pharmaceutical formulations and biological fluids was urgently required from this point forward. A reaction between fluorescamine and the aliphatic amino moiety found in both drugs was performed in a slightly alkaline borate buffer (pH 8.5) resulted in highly fluorescent products measured at λ_em 460 (after λ_ex 390.5 nm). Linear calibration curves were constructed over the concentration range of 70 to 1800 ng mL^-1 and 100 to 1400 ng mL^-1 , with slope values of 0.273 and 0.286, correlation coefficients of 0.9998 and 0.9997, and determination coefficient of 0.9997 and 0.9994 for Poly B and CS, respectively. The ultra sensitivity of the proposed method was demonstrated by the very low limits of quantifications values of 67.56 ng mL^-1 and 94.89 ng mL^-1 for Poly B and CS, respectively. The cited drugs were successfully determined in their intravenous market preparations by the prescribed method. Moreover, due to the high sensitivity, the suggested method was employed to assay the investigated drugs in biological fluids.

Selective Spectrofluorimetric Protocol for Determination of Commonly Used Gram-negative Bactericidal Drug in Combined Pharmaceutical Dosage Forms and Human Plasma

Gram-negative bacteria cause infections such as skin infection, meningitis, and pneumonia in human being. Gram-negative bacteria are highly resistant to most availaible bactericidal drugs. One of the most commonly used Gram-negative bactericidal drug is Polymyxin B sulfate (PMS). In addition, it is used in cases of highly resistant Gram-negative bacterial infections. The widespread of PMS necessitate the development of an exceedingly sensitive and selective fluorimetric assay for its determination in pure form, different pharmaceutical dosage forms, and human plasma. The presented method is used to determine PMS in their dosage form (vials) and combined pharmaceutical formulations (skin and eye ointments) with a high degree of accuracy and selectivity. The described procedure relies on the structure of a derivative of a high degree of fluorescence called dihydropyridine, via the condensation of the amino moiety of PMS with two equivalents of acetylacetone in the presence of formaldehyde and Teorell buffer (pH = 3). The fluorescent product was measured at 471 nm (λ_ex = 402 nm). The linearity ranged from 100-3000 ng mL^-1 of PMS with an excellent r² of 0.9998. LOD and LOQ were 27.16 ng mL^-1 and 82.30 ng mL^-1, respectively. Owing to the developed method's high selectivity, it was successfully utilized for assay of PMS, in the ointment, in the presence of oxytetracycline as an active ingredient. Furthermore, the procedure applied for the estimation of parenteral PMS in human plasma with very good mean recovery 97.42 ± 1.46.

Polymyxin Delivery Systems: Recent Advances and Challenges

Polymyxins are vital antibiotics for the treatment of multiresistant Gram-negative ESKAPE pathogen infections. However, their clinical value is limited by their high nephrotoxicity and neurotoxicity, as well as their poor permeability and absorption in the gastrointestinal tract. This review focuses on various polymyxin delivery systems that improve polymyxin bioavailability and reduce drug toxicity through targeted and controlled release. Currently, the most suitable systems for improving oral, inhalation, and parenteral polymyxin delivery are polymer particles, liposomes, and conjugates, while gels, polymer fibers, and membranes are attractive materials for topical administration of polymyxin for the treatment of infected wounds and burns. In general, the application of these systems protects polymyxin molecules from the negative effects of both physiological and pathological factors while achieving higher concentrations at the target site and reducing dosage and toxicity. Improving the properties of polymyxin will be of great interest to researchers who are focused on developing antimicrobial drugs that show increased efficacy and safety.