Adsorption and sensing of CO and NH3 on chemically modified graphene surfaces

We have studied the electronic structure and adsorption characteristics of environmentally potent gaseous molecules like carbon monoxide (CO) and ammonia (NH₃) on chemically modified surfaces of graphene, employing ab initio density functional methods. An insight into the changes made in the electronic band structure due to intrinsic and extrinsic doping and through a combined effect of both is discussed. With this regard, the adsorption of these gaseous moieties is investigated on substitutionally p- and n- doped graphene surfaces, doped with various mole fractions and having different configurational patterns on the surface. Even though the electronic properties are modified with various mole fractions of doping they do not show a methodical increase with the increase in the dopant concentration. This is attributed to the sub-lattice induced symmetry breaking for the dopant configurations where equivalent lattice sites are occupied on the surface. An appreciable band gap opening of around 0.63 eV is observed on doping, due to sub-lattice symmetry breaking. This is further improved on molecular doping, with CO and NH₃, where an increase up to 0.83 eV is noted with adsorption of ammonia. While both the molecules are physisorbed on nitrogen doped surfaces, carbon monoxide is strongly physisorbed and ammonia molecules are chemisorbed on a few boron doped surfaces resulting in notable changes in the adsorption energy. Therefore, it is clear that changes in the transport properties can be brought about by adsorption of these molecules on such surfaces and this study clearly indicates the invaluable prospects of such doped surfaces as potential sensors for these molecules.

We have studied the electronic structure and adsorption characteristics of environmentally potent gaseous molecules like carbon monoxide (CO) and ammonia (NH₃) on chemically modified surfaces of graphene, employing ab initio density functional methods.     

Kinetics and Characterization of Non-enzymatic Fragmentation of Monoclonal Antibody Therapeutics

Purpose

To understand non-enzymatic hydrolytic fragmentation of a monoclonal antibody therapeutic under temperature stressed conditions and investigating possible mechanism for the same.

Methods

The mAb therapeutic was incubated at 50°C in phosphate buffer at pH 6.5 and fragmentation was monitored at different ionic strengths under stressed conditions. The incubated mAb was sampled at regular time intervals by analytical Size Exclusion Chromatography (SEC).

Results

It was observed that 57% of the mAb product fragmented over 4 days into two fragment species – Fc-Fab and Fab with molecular weights of 97 KDa and 47 KDa, respectively, as measured by mass spectrometry (MS) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The fragmentation rate was slow initially and then accelerated with time. No change in % aggregate level was observed in this duration, implying that degradation was primarily via fragmentation at high temperature. Kinetics of hydrolytic fragmentation was hypothesized and SEC data was fitted to estimate the kinetic rate constants. While degradation of the monomer into fragment species was non-Arrhenius with a negative activation energy, further degradation of Fab-Fc fragments into Fab or Fc fragments followed Arrhenius Law with an activation energy of 2.1 and 15.38 kcal/mol, respectively.

Conclusion

High temperature (50°C) causes mAb to cleave at the hinge region to form Fab-Fc and Fab/Fc, as confirmed by dynamic light scattering, SDS-PAGE, SEC, and MS. A kinetic model for hydrolytic fragmentation has been proposed. The results are expected to assist end users in formulation development as well as in monitoring stability of biotherapeutic products.

     

Intravesical botulinum toxin A injections in the treatment of painful bladder syndrome/interstitial cystitis: a systematic review

Introduction and hypothesis  

Intravesical botulinum toxin A (BTX-A) is emerging as a potential new treatment for refractory interstitial cystitis (IC). However, there has been conflicting evidence on this treatment's effectiveness. The aim of our systematic review was to assess the effectiveness and adverse effects of intravesical BTX-A in IC.     

Discovery and Structure Optimization of a Series of Isatin Derivatives as Mycobacterium tuberculosis Chorismate Mutase Inhibitors

In this study, the crystal structure of the Mycobacterium tuberculosis (MTB) enzyme chorismate mutase (CM) bound to transition state analogue (PDB: 2FP2) was used as a framework for virtual screening of the BITS‐Pilani in‐house database (2500 compounds) to identify new scaffold. We identified isatin as novel small molecule MTB CM inhibitors; further twenty‐four isatin derivatives were synthesized and evaluated in vitro for their ability to inhibit MTB CM, and activity against M. tuberculosis as steps towards the derivation of structure–activity relationships (SAR) and lead optimization. Compound 3‐(4‐nitrobenzylidene)indolin‐2‐one, 24 emerged as the most promising lead with an IC₅₀ of 1.01 ± 0.22 μm for purified CM and MIC of 23.5 μm for M. tuberculosis, with little or no cytotoxicity.     

Spirulina attenuates cyclosporine-induced nephrotoxicity in rats

Cyclosporine (CsA) causes a dose-related decrease in renal function in experimental animals and humans. The generation of reactive oxygen species (ROS) has been implicated in CsA-induced nephrotoxicity. It was previously shown that Spirulina, a blue-green algae, with antioxidant properties effectively attenuated the doxorubicin-induced cardiotoxicity in mice and cisplatin-induced nephrotoxicity in rat. The present study investigated the nephroprotective role of Spirulina against CsA-induced nephrotoxicity in rats. Spirulina (500 mg kg(-1) b.w.) was administered orally for 3 days before and 14 days concurrently with CsA (50 mg kg-1 b.w.). Rats treated with CsA showed nephrotoxicity as evidenced from a significant elevation in plasma urea, creatinine, urinary N-acetyl-beta-D-glucosaminidase (beta-NAG) and a decrease in creatinine and lithium clearance. Pretreatment with Spirulina protected the rats from CsA-induced nephrotoxicity. The CsA-induced rise in plasma urea and creatinine and the decrease in creatinine and lithium clearance were attenuated by Spirulina. There was a significant increase in plasma and kidney tissue MDA with CsA. Spirulina prevented the rise in plasma and kidney tissue MDA. Histopathology of the kidney from CsA-treated rats showed severe isometric vacuolization and widening of the interstitium. However, pretreatment with Spirulina prevented such changes, and the kidney morphology was comparable to that of the control. Spirulina treatment did not alter the blood CsA levels. These results suggest that Spirulina has a protective effect against nephrotoxicity induced by CsA. This study further supports the crucial role of the antioxidant nature of Spirulina in protecting against CsA-induced oxidative stress.     

Protection against cisplatin-induced nephrotoxicity by Spirulina in rats

Purpose: Cisplatin (CP)-induced nephrotoxicity is associated with the increased generation of reactive oxygen metabolites and lipid peroxidation in kidney, caused by the decreased levels of antioxidants and antioxidant enzymes. The purpose of this study was to evaluate the role of Spirulina, blue–green alga with antioxidant properties, in the protection of cisplatin-induced nephrotoxicity in rat. Methods: Rats were treated with CP (6 mg/kg bw, single dose, intraperitoneally). Spirulina (1,000 mg/kg) was administered orally for 8 days and CP treatment was given on day 4. Nephrotoxicity was assessed, 6 days after the CP treatment, by measuring plasma urea, creatinine, urinary N-acetyl-(d-glucose-aminidase) (β-NAG) and histopathology of kidney. Results: Rats treated with CP showed marked nephrotoxicity as evidenced from the significant elevation in plasma urea, creatinine and urinary β-NAG. Histological assessment revealed marked proximal tubular necrosis and extensive epithelial vacuolization in the kidney of CP-treated rats. Superoxide dismutase, catalase and glutathione peroxidase were decreased and lipid peroxidation was increased in kidney tissue. Pretreatment with Spirulina protected the rats from CP-induced nephrotoxicity. The rise in plasma urea, creatinine, urinary β-NAG, plasma and kidney tissue MDA and histomorphological changes were significantly attenuated by Spirulina. In vitro studies using human ovarian cancer cells revealed that Spirulina did not interfere with the cytotoxic effects of CP on tumor cells. Conclusions: In summary, Spirulina significantly protected the CP-induced nephrotoxicity through its antioxidant properties.