Development and Validation of Stability-indicating HPLC Method for Simultaneous Estimation of Cefixime and Linezolid

A stability-indicating reverse phase high performance liquid chromatography method was developed and validated for cefixime and linezolid. The wavelength selected for quantitation was 276 nm. The method has been validated for linearity, accuracy, precision, robustness, limit of detection and limit of quantitation. Linearity was observed in the concentration range of 2-12 μg/ml for cefixime and 6-36 μg/ml for linezolid. For RP-HPLC, the separation was achieved by Phenomenex Luna C₁₈ (250×4.6 mm) 5 μm column using phosphate buffer (pH 7):methanol (60:40 v/v) as mobile phase with flow rate 1 ml/min. The retention time of cefixime and linezolid were found to be 3.127 min and 11.986 min, respectively. During force degradation, drug product was exposed to hydrolysis (acid and base hydrolysis), H₂O₂, thermal degradation and photo degradation. The % degradation was found to be 10 to 20% for both cefixime and linezolid in the given condition. The method specifically estimates both the drugs in presence of all the degradants generated during forced degradation study. The developed methods were simple, specific and economic, which can be used for simultaneous estimation of cefixime and linezolid in tablet dosage form.     

Selective Laser Sintering 3-Dimensional Printing as a Single Step Process to Prepare Amorphous Solid Dispersion Dosage Forms for Improved Solubility and Dissolution Rate

This study reports the development of ritonavir-copovidone amorphous solid dispersions (ASDs) and dosage forms thereof using selective laser sintering (SLS) 3-dimensional (3-D) printing in a single step, circumventing the post-processing steps required in common techniques employed to make ASDs. For this study, different drug loads of ritonavir with copovidone were processed at varying processing conditions to understand the impact, range, and correlation of these parameters for successful ASD formation. Further, ASDs characterized using conventional and advanced solid-state techniques including wide-angle X-ray scattering (WAXS), solid-state nuclear magnetic resonance (ssNMR), revealed the full conversion of the crystalline drug to its amorphous form as a function of laser-assisted selective fusion in a layer-by-layer manner. It was observed that an optimum combination of the powder flow properties, surface temperature, chamber temperature, laser speed, and hatch spacing was crucial for successful ASD formation, any deviations resulted in print failures or only partial amorphous conversion. Moreover, a 21-fold increase in solubility was demonstrated by the SLS 3-D printed tablets. The results confirmed that SLS 3-D printing can be used as a single-step platform for creating ASD-based pharmaceutical dosage forms with a solubility advantage.     

Modification of nano-silver bioactivity by adsorption on carbon nanotubes and graphene oxide

Abstract

Objective: The toxicity of silver nanomaterials in various forms has been extensively evaluated, but the toxicity of silver nanocarbon composites is less well understood. Therefore, silver-carbon nanotube composites (Ag-MWCNT-COOH) and silver-graphene oxide composites (Ag-GO) were synthesized by microwave irradiation and evaluated in two in vitro cell models.

Materials/Methods: Toxicity of silver nanosphere (Ag), Ag-MWCNT-COOH and Ag-GO were analyzed by MTS assay and LDH assay in primary C57BL/6 murine alveolar macrophages and human THP-1 cells. Activation of NLRP3 inflammasome by particle variants in these models was done by proxy using LPS co-culture and IL-1β release.

Results: The results depended on the model, as the amount of Ag on the modified carbon resulted in slightly increased toxicity for the murine cells, but did not appear to affect toxicity in the human cell model. IL-1β release from carbon particle-exposures was decreased by the presence of Ag in both cell models. Suspensions of Ag-MWCNT-COOH, Ag-GO and Ag in artificial lysosomal fluid were prepared and ICP-MS was used to detect Ag ions concentration in three silver suspension/solutions. The amount of Ag ions released from Ag-MWCNT-COOH and Ag-GO were similar, which were both lower than that of Ag nanospheres.

Conclusions: The results suggest the bioactivity of silver composites may be related to the amount of Ag ions released, which can be dependent on the cell model under investigation.     

PEGylation of a High-Affinity Anti-(+)Methamphetamine Single Chain Antibody Fragment Extends Functional Half-Life by Reducing Clearance

Purpose

Methamphetamine (METH) abuse is a worldwide drug problem, yet no FDA-approved pharmacological treatments are available for METH abuse. Therefore, we produced an anti-METH single chain antibody fragment (scFv7F9Cys) as a pharmacological treatment for METH abuse. ScFv’s have a short half-life due to their small size, limiting their clinical use. Thus, we examined the pharmacokinetic effects of conjugating poly(ethylene) glycol (-PEG) to scFv7F9Cys to extend its functional half-life.

Methods

The affinity of scFv7F9Cys and PEG conjugates to METH was determined in vitro via equilibrium dialysis saturation binding. Pharmacokinetic and parameters of scFv7F9Cys and scFv7F9Cys-PEG20K (30 mg/kg i.v. each) and their ability to bind METH in vivo were determined in male Sprague-Dawley rats receiving a subcutaneous infusion of METH (3.2 mg/kg/day).

Results

Of three PEGylated conjugates, scFv7F9Cys-PEG20K was determined the most viable therapeutic candidate. PEGylation of scFv7F9Cys did not alter METH binding functionality in vitro, and produced a 27-fold increase in the in vivo half-life of the antibody fragment. Furthermore, total METH serum concentrations increased following scFv7F9Cys or scFv7F9Cys-PEG20K administration, with scFv7F9Cys-PEG20K producing significantly longer changes in METH distribution than scFv7F9Cys.

Conclusions

PEGylation of scFv7F9Cys significantly increase the functional half-life of scFv7F9Cys, suggesting it may be a long-lasting pharmacological treatment option for METH abuse.

     

Beta-carotene micellarization during in vitro digestion and uptake by Caco-2 cells is directly proportional to beta-carotene content in different genotypes of cassava

Cassava, a staple food in sub-Saharan Africa, does not provide adequate amounts of pro-vitamin A (VA) carotenoids and has been targeted for biofortification (i.e. selectively breeding cultivars of increased nutrient density with agroeconomically acceptable characteristics). However, the accessibility of pro-VA carotenoids for absorption in different cultivars of cassava remains unknown. Here, we used the coupled in vitro digestion/Caco-2 cell uptake model to screen the relative accessibility of beta-carotene (betaC) in 10 cultivars of cassava with varying concentrations of betaC. After cooking (boiled for 30 min), the betaC concentration in tubers from different cultivars ranged from less than detectable to 6.9 microg betaC/g cassava. Samples were subjected to simulated oral, gastric, and small intestinal digestion to determine stability and micellarization of betaC. All-trans betaC, 9-cis betaC, and 13-cis betaC were the most abundant carotenoids in cooked cassava and recoveries after digestion exceeded 70%. Efficiency of micellarization of total betaC was 30 +/- 2% for various cultivars with no significant difference in isomers and linearly proportional to concentration in cooked cassava (r = 0.87; P < 0.001). Accumulation of all-trans betaC by Caco-2 cells incubated with the diluted micelle fraction for 4 h was proportional (R(2) = 0.99; P < 0.001) to the quantity present in micelles. These results suggest that all-trans betaC content appears to provide the key selection marker for breeding cassava to improve VA status and that the more complicated screening procedure using in vitro digestion coupled to cell uptake does not provide additional information on potential bioavailability.     

Impact of Opiate–HIV-1 Interactions on Neurotoxic Signaling

Opiate drug abuse exacerbates the pathogenesis of human immunodeficiency virus-1 (HIV-1) in the central nervous system through direct actions on glia and neurons. Opiate abuse causes widespread disruption of astroglial and microglial function, and significant increases in astroglial-derived proinflammatory cytokines and chemokines, which likely contributes to neuronal dysfunction, death, and HIV encephalitis. Neurons are also directly affected by opiate–HIV-1 interactions. HIV-1 and the viral proteins gp120 and Tat activate multiple caspase-dependent and caspase-independent proapoptotic pathways in neurons involving phosphatidylinositol 3-kinase (PI3 kinase)/Akt, as well as p38, c-Jun N-terminal kinase (JNK) and/or other mitogen-activated protein kinases (MAPKs). Opiates appear to decrease the threshold for HIV-1-mediated neurotoxicity by sending convergent signals that exacerbate proapoptotic events induced by viral and cellular toxic products. The synergistic proinflammatory and neurotoxic effects of opiate drugs on glia and neurons are largely mediated through μ opioid receptors, which are expressed by subpopulations of astroglia, microglia, and neurons. Opiate abuse intrinsically modifies the host response to HIV-1. Identification of how this occurs is providing considerable insight toward understanding the mechanisms underlying HIV-1-associated dementia.     

Stabilization of turbidimetric immunoassay by covalent coupling of antibody to latex particles.

Turbidimetric immunoassay is commonly used to quantify serum proteins. Latex-particle enhancement of this type of assay has been primarily associated with increasing assay sensitivity. However, covalent coupling of an antibody to a latex particle can offer other advantages that are also pertinent in measurement of high concentrations of analytes. By using a common antibody with IgG as a model analyte, we describe the development of a nonenhanced and a latex-particle-enhanced turbidimetric assay for measuring serum IgG. Both assays show adequate analytical recovery and parallelism, and results compare well with those by rate nephelometry. The latex-enhanced assay has equivalent sensitivity, working range, and interassay precision, but much greater signal change and calibration stability than the nonenhanced assay. In addition, with latex particles, less antiserum is needed. Coupling antibodies to latex particles offers considerable advantages, even when an improved assay detection limit is not required.     

Chronic untreated tuberculous meningitis

Summary We describe a 34-year-old man who suffered from tuberculous meningitis for 2 years without receiving antituberculous medication. Our case is compared with other forms of indolent or benign variants of the disease.     

Bioengineering and regeneration of gastrointestinal tissue: where are we now and what comes next?

Introduction: The field of tissue engineering and regenerative medicine has been applied to the gastrointestinal (GI) tract for a couple decades. Several achievements have been accomplished that provide promising tools for treating diseases of the GI tract.

Areas covered: The work described in this review covers the traditional aspect of using cells and scaffolds to replace parts of the tract. Several studies investigated different types of biomaterials and different types of cells. A more recent approach involved the use of gut-derived organoid units that can differentiate into all gut cell layers. The most recent approach introduced the use of organ-on-a-chip concept to understand the physiology and pathophysiology of the GI system.

Expert opinion: The different approaches tackle the diseases of the GI tract from different perspectives. While all these different approaches provide a promising and encouraging future for this field, the translational aspect is yet to be studied.     

Effect of subinhibitory concentrations of ciprofloxacin on Mycobacterium fortuitum mutation rates

OBJECTIVES: Fluoroquinolones have found a place in the management of mycobacterial diseases including tuberculosis. It has been previously shown that subinhibitory concentrations of quinolones increase the mutation rate in Escherichia coli and staphylococci. The purpose of this study is to extend this observation to mycobacteria and to quantify mutation rates. METHODS: The mutation rate in Mycobacterium fortuitum to ciprofloxacin, levofloxacin, moxifloxacin, rifampicin, erythromycin and gentamicin resistance was determined when grown with and without various sub-MIC concentrations of ciprofloxacin. RESULTS: M. fortuitum exposed to 1/2 MIC ciprofloxacin had an increase in the mutation rate of between 72- and 120-fold when selected on quinolones or other antimycobacterial antibiotics. Smaller, but significant increases in mutation rate were seen when the organism was exposed to lower concentrations (1/4 MIC and 1/8 MIC). CONCLUSIONS: These data show that sub-MIC concentrations of fluoroquinolone significantly increase mutation rates and these data suggest that care must be taken to ensure that bacteria are not exposed to subinhibitory concentrations when adding quinolones to a regimen used to treat mycobacterial infection.