Mahantesh Jadhav

Solid lipid nanoparticles of clotrimazole silver complex: An efficient nano antibacterial against Staphylococcus aureus and MRSA.

New and effective strategies to transform current antimicrobials are required to address the increasing issue of microbial resistance and declining introduction of new antibiotic drugs. In this context, metal complexes of known drugs and nano delivery systems for antibiotics are proving to be promising strategies. The aim of the study was therefore to synthesize a silver complex of clotrimazole and formulate it into a nano delivery system for enhanced and sustained antibacterial activity against susceptible and resistant Staphylococcus aureus. A silver complex of clotrimazole was synthesized, characterized and further encapsulated into solid lipid nanoparticles to evaluate its antibacterial activity against S. aureus and methicillin-resistant S. aureus (MRSA). An in vitro cytotoxicity study was performed on HepG2 cell lines to assess the overall biosafety of the synthesized clotrimazole silver complex to mammalian cells, and was found to be non-toxic to mammalian cells (cell viability >80%). The minimum inhibitory concentrations (MIC) of clotrimazole and clotrimazole-silver were 31.25 and 9.76 μg/mL against S. aureus, and 31.25 and 15.62 against MRSA, respectively. Clotrimazole SLNs exhibited MIC values of 104 and 208 μg/mL against both MSSA and MRSA at the end of 18 and 36 h, respectively, but thereafter completely lost its antibacterial activity. Clotrimazole-silver SLNs had an MIC value of 52 μg/mL up to 54 h, after which the MIC value was 104 μg/mL against both strains at the end of 72 h. Thus, clotrimazole-silver SLNs was found to be an efficient nanoantibiotic.

Co-encapsulation of multi-lipids and polymers enhances the performance of vancomycin in lipid–polymer hybrid nanoparticles: In vitro and in silico studies

Nano-drug delivery systems are being widely explored to overcome the challenges with existing antibiotics to treat bacterial infections [1]. Lipid-polymer hybrid nanoparticles (LPNs) display unique advantages of both liposomes and polymeric nanoparticles while excluding some of their limitations, particularly the structural integrity of the polymeric particles and the biomimetic properties of the liposome [1]. The use of helper lipids and polymers in LPNs has not been investigated, but has shown potential in other nano-drug delivery systems to improve drug encapsulation, antibacterial activity and drug release. Therefore, LPNs using co-excipients were prepared using vancomycin (VCM), glyceryl triplamitate and Eudragit RS100 as the drug, lipid and polymer respectively. Oleic acid (OA), Chitosan (CHT) and Sodium alginate (ALG) were explored as co-excipients. Results indicated rod-shaped LPNs with suitable size, PDI and zeta potential, while encapsulation efficiency (%EE) increased from 27.8% to 41.5%, 54.3% and 69.3% with the addition of OA, CHT and ALG respectively. Drug release indicated that VCM-CHT had the best performance in sustained drug release of 36.1 ± 5.35% after 24h. The EE and drug release were further corroborated by in silico and release kinetics data. In vitro antibacterial studies of all formulations exhibited better activity against bare VCM and sustained activity up to day 5 against both Staphylococcus aureus and MRSA, with VCM-OA and VCM-CHT showing better activity against MRSA. Therefore, this LPN proves to be a promising system for delivery of VCM as well as other antibiotics.

Pegylated oleic acid: A promising amphiphilic polymer for nano-antibiotic delivery

Graphical abstract Figure. No caption available. Abstract Vancomycin (VM), a last resort to control methicillin‐resistant S. aureus (MRSA) infections, is on the verge of becoming ineffective. Novel nano delivery systems of VM have the potential to combat MRSA. The search for novel materials for nanoantibiotic development is therefore an active research area. In this study, oleic acid (OA) was coupled with monomethoxy polyethylene glycol (mPEG) to obtain a novel bio‐safe amphiphilic polymer, mPEG‐OA. The critical micelle concentration of mPEG‐OA, was found to be 4.5 × 10−8 m/L. VM‐loaded polymersomes were prepared from mPEG‐OA and evaluated for size, polydispersity index (PDI), zeta potential (ZP), surface morphology, drug release, in vitro and in vivo antibacterial activity. The size, PDI and ZP of VM‐loaded polymersomes were 142.9 ± 7.5 nm, 0.228 ± 0.03 and −18.3 ± 3.55 mV respectively. Transmission electron microscopy images revealed the spherical shape of polymersomes. The encapsulation efficiency was 53.64 ± 1.86%. The drug release from polymersomes was sustained and in vitro antibacterial activity was 42‐ and 5‐fold more against S. aureus and MRSA, compared with plain VM. An in vivo BALB/c mice, skin infection models revealed that treatment with VM‐loaded polymersomes significantly reduced the MRSA burden compared with plain VM and blank polymersomes. There was a 183 and a 25‐fold reduction in the MRSA colony finding units load in mice skin treated with VM‐loaded polymersomes compared to that treated with blank polymersomes and bare VM respectively. In summary, the developed VM‐loaded polymersomes from novel mPEG‐OA polymer were found to be a promising nanoantibiotic against MRSA.

Transforming linoleic acid into a nanoemulsion for enhanced activity against methicillin susceptible and resistant Staphylococcus aureus

The activity of antibacterial agents can be enhanced by transforming them into the nano form. The aim of this study was therefore to enhance the antibacterial activity of linoleic acid (LA) against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) by formulating it as a nanoemulsion (NE). The mean globule diameter, polydispersity index and zeta potential of the optimized LA NE containing benzalkonium chloride (BAC) as a stabilizer were 75.14 ± 3 nm, 0.145 ± 0.01 and 45.7 ± 1.27 mV respectively. The turbidity absorbance, conductivity and viscosity were 1.773 ± 0.69, 0.0508 ± 0.006 mS cm−1 and 92.74 ± 2.17 mPas respectively, and the formulation was stable at 4 °C for 3 months. The LA NE was non-toxic and exhibited a 205-fold greater increase in the antibacterial activity than plain LA against S. aureus and MRSA. The fractional inhibitory concentration values indicated that the combination of LA and BAC had a synergistic effect. The molecular modeling studies revealed better stability of the LA–BAC system than LA with other surfactants. Bacterial protein degradation and cell morphology studies confirmed that the antibacterial activity of LA NE was due to cell membrane damage. These findings suggest that the developed LA NE could be a promising non-antibiotic drug containing antibacterial nano delivery system.

Synthesis of 11-(Piperazin-1-yl)-5H-dibenzo[b,e] [1,4]diazepine on Kilo Scale

A synthesis of 11-(piperazin-1yl)-5 H-dibenzo[b,e][1,4]diazepine on kilo scale without any chromatographic purification step is reported. Key steps involved are Ullmann condensation, catalytic hydrogenation, and catalyzed cyclization.

pH-responsive chitosan nanoparticles from a novel twin-chain anionic amphiphile for controlled and targeted delivery of vancomycin

The design and synthesis of novel pH-responsive nanoantibiotics is an emerging research area to address the antibiotic resistance crisis. The purpose of this study was therefore to synthesize a new anionic gemini surfactant (AGS) that could result in the formulation of pH-responsive chitosan nanoparticles (CSNPs) to treat methicillin-resistant Staphylococcus aureus (MRSA) infections. The coupling of oleic acid with 2,2-dimethyl-5,5-bis(hydroxymethyl)-1,3-dioxane and subsequent deprotection followed by a reaction with succinic anhydride and sodium bicarbonate yielded AGS. Critical micelle concentration (CMC) was determined using conductometry and in vitro cytotoxicity was performed using a MTT assay. Vancomycin loaded CSNPs containing AGS (DL_CSSNPs) were prepared by ionotropic gelation of chitosan with pentasodium tripolyphosphate. CSNPs were characterized for size, polydispersity index (PDI), zeta potential (ZP), entrapment efficiency, surface morphology, in vitro drug release and in vitro antibacterial activity (at pH 6.5 and 7.4). Results from the in vitro antibacterial activity were further supported by an in vivo study using a mice skin infection model. The CMC of AGS was found to be 1.3mM/L and it was non-toxic. The DL_CSSNPs were spherical with size, PDI and ZP of 220.57±5.9nm, 0.299±0.004 and 21.9±0.9mV respectively. An increase in the vancomycin release from the DL_CSSNPs was observed at pH 6.5 compared to pH 7.4. The minimum inhibitory concentration values at pH 6.5 and 7.4 against MRSA were 7.81 and 62.5μg/ml respectively. In vivo antibacterial activity showed that the MRSA burden in mice treated with DL_CSSNPs was reduced by almost 8-fold compared to those treated with pure vancomycin.

Direct and Indirect Drug Design Approaches for the Development of Novel Tricyclic Antipsychotics: Potential 5-HT2A Antagonist

Schizophrenia is a mental disorder manifested largely by disintegration of thought processes and emotional responsiveness. Given the therapeutic and toxic limitations of clinically available drugs, it is clear that there is still a need for the development of new generation antipsychotic agents with an improved clinical profile. Development of novel hybrid atypical tricyclic antipsychotic pharmacophore was achieved using direct (by measuring docking score of designed molecules on modelled 5- receptor) and indirect (current, clinically available therapeutic agents’ data) drug design approaches.

Non-ionic self-assembling amphiphilic polyester dendrimers as new drug delivery excipients

Solubility enhancement of poorly soluble antibiotics via self-assembling nano systems could be a promising approach to effectively treat bacterial infections in the current scenario of evolving resistant species. The study in this paper reports the synthesis of novel biocompatible G2 and G3 polyester amphiphilic dendrimers (ADs) (GMOA-G2-OH, GMOA-G3-OH, GMS-G2-OH and GMS-G3-OH) and their application as: (i) solubility enhancers for fusidic acid (FSD) as a model antibiotic with poor aqueous solubility and (ii) as stearic stabilizers in the preparation of solid lipid nanoparticles (SLNs). Two different series of ADs from glycerol monostearate (GMS) and glycerol monooleate (GMOA) were synthesized and their structures were confirmed employing FT-IR, NMR (1H and 13C) and HR-MS. The MTT assay confirmed their non-toxicity to mammalian cells. The critical aggregation concentration value order for ADs was GMS-G3-OH (5 × 10−6 mol l−1) < GMOA-G3-OH (7 × 10−6 mol l−1) < GMOA-G2-OH = GMS-G2-OH (5 × 10−5 mol l−1). All ADs formed micelles in the size range of 6.48 ± 0.04 nm to 12.38 ± 0.36 nm. At 1% w/w concentration FSD solubility enhancement in GMOA-G2-OH, GMOA-G3-OH, GMS-G2-OH and GMS-G3-OH was 43, 11, 9.1 and 6.8-fold respectively compared to water. As GMOA-G2-OH enabled the highest solubility of FSD, it was further evaluated for its antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). The minimum inhibitory concentration values for FSD with and without GMOA-G2-OH against S. aureus were 0.23 μg ml−1 and 0.53 μg ml−1 respectively whereas the values were 0.23 μg ml−1 and 0.39 μg ml−1 against MRSA respectively. These results suggested that GM-OA-G2 not only enhanced the solubility but also enhanced antibacterial potency of FSD. Furthermore, these ADs showed their potential as promising pharmaceutical excipients as they acted as stearic stabilizers in the preparation of SLNs. Using these ADs stable SLNs with zeta potential value in the range of −15.30 ± 1.44 to −38.46 ± 3.04 were formed.

A hybrid of mPEG-b-PCL and G1-PEA dendrimer for enhancing delivery of antibiotics

&NA; The development of novel materials is essential for the efficient delivery of drugs. Therefore, the aim of the study was to synthesize a linear polymer dendrimer hybrid star polymer (3‐mPEA) comprising of a generation one poly (ester‐amine) dendrimer (G1‐PEA) and a diblock copolymer of methoxy poly (ethylene glycol)‐b‐poly(&egr;‐caprolactone) (mPEG‐b‐PCL) for formulation of nanovesicles for efficient drug delivery. The synthesized star polymer was characterized by FTIR, 1H and 13C NMR, HRMS, GPC and its biosafety was confirmed by MTT assays. Thereafter it was evaluated as a nanovesicle forming polymer. Vancomycin loaded nanovesicles were characterized using in vitro, molecular dynamics (MD) simulations and in vivo techniques. MTT assays confirmed the nontoxic nature of the synthesized polymer, the cell viability was 77.23 to 118.6%. The nanovesicles were prepared with size, polydispersity index and zeta potential of 52.48 ± 2.6 nm, 0.103 ± 0.047, −7.3 ± 1.3 mV respectively, with the encapsulation efficiency being 76.49 ± 2.4%. MD simulations showed spontaneous self‐aggregation of the dendritic star polymer and the interaction energy between the two monomers was −146.07 ± 4.92, Van der Waals interactions playing major role for the aggregates stability. Human serum albumin (HSA) binding studies with Microscale Thermophoresis (MST) showed that the 3‐mPEA did not have any binding affinity to the HSA, which showed potential for long systemic circulation. The vancomycin (VCM) release from the drug loaded nanovesicles was found to be slower than bare VCM, with an 65.8% release over a period of 48 h. The in vitro antibacterial test revealed that the drug loaded nanovesicles had 8‐ and 16‐fold lower minimum inhibitory concentration (MIC) against methicillin sensitive Staphylococcus aureus and methicillin‐resistant S. aureus strains (MRSA) compared to free drug. The flow cytometry study showed 3.9‐fold more dead cells of MRSA in the population when samples were treated with the drug loaded nanovesicles than the bare VCM at concentration 0.488 &mgr;g/mL. An in vivo skin infection mice model showed a 20‐fold reduction in the MRSA load in the drug loaded nanovesicles treated groups compared to bare VCM. These findings confirmed the potential of 3‐mPEA as a promising biocompatible effective nanocarrier for antibiotic delivery. Graphical abstract Figure. No caption available.

Synthesis of an oleic acid based pH-responsive lipid and its application in nanodelivery of vancomycin

Graphical abstract Figure. No Caption available. Abstract Stimuli‐responsive nano‐drug delivery systems can optimize antibiotic delivery to infection sites. Identifying novel lipids for pH responsive delivery to acidic conditions of infection sites will enhance the performance of nano‐drug delivery systems. The aim of the present investigation was to synthesize and characterize a biosafe novel pH‐responsive lipid for vancomycin delivery to acidic conditions of infection sites. A pH‐responsive solid lipid, N‐(2‐morpholinoethyl) oleamide (NMEO) was synthesized and used to prepare vancomycin (VCM)‐loaded solid lipid nanoparticles (VCM_NMEO SLNs). The particle size (PS), polydispersity index (PDI), zeta potential (ZP) and entrapment efficiency (EE) of the formulation were 302.8 ± 0.12 nm, 0.23 ± 0.03, −6.27 ± 0.017 mV and 81.18 ± 0.57% respectively. The study revealed that drug release and antibacterial activity were significantly greater at pH 6.0 than at pH 7.4, while the in silico studies exposed the molecular mechanisms for improved stability and drug release. Moreover, the reduction of MRSA load was 4.14 times greater (p < 0.05) in the skin of VCM_NMEO SLNs treated mice than that of bare VCM treated specimens. Thus, this study confirmed that NMEO can successfully be used to formulate pH‐responsive SLNs with potential to enhance the treatment of bacterial infections.