Sanjeev Rambharose

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.

Monolayered multipolymeric buccal films with drug and polymers of opposing solubilities for ARV therapy: physico-mechanical evaluation and molecular mechanics modelling.

Although buccal permeation investigations with antiretroviral drug solutions have confirmed their transbuccal delivery potential, studies on their formulation into delivery systems are lacking. Multipolymeric monolayered films (MMFs) with drugs and polymers of opposing solubilities will offer several advantages for the controlled release delivery of didanosine (DDI) via the buccal route. The aim of this study was to employ a co-blending-co-plasticization technique for preparation of MMFs containing Eudragit(®) RS 100 (EUD) and Hydroxypropyl methylcellulose (HPMC) and to undertake molecular modelling and in vitro characterizations. Uniform drug content (91-105%) with low variability was obtained for all films. Co-blending of DDI:HPMC:EUD (1:1:10) was required to achieve controlled drug release. The buccal permeability potential of DDI from the MMFs was successfully demonstrated with a permeability coefficient of 0.72±0.14×10(-2) cm/h and a steady state flux of 71.63±13.54 μg/cm(2) h. Films had acceptable mucoadhesivity (2184 mN), mechanical strength (0.698 N/mm(2)) and surface pH (6.63). The mechanism inherent to the mucoadhesive and drug release profile performance of the MMFs was elucidated via static lattice molecular mechanics simulations wherein a close corroboration among the in vitro-in silico (IVIS) data was observed. These extensive physico-mechanical and molecular atomistic studies have confirmed the use of MMFs containing DDI, HPMC and EUD as a buccal delivery system.

Ultra-small lipid-dendrimer hybrid nanoparticles as a promising strategy for antibiotic delivery: In vitro and in silico studies

The purpose of this study was to explore the preparation of a new lipid-dendrimer hybrid nanoparticle (LDHN) system to effectively deliver vancomycin against methicillin-resistant Staphylococcus aureus (MRSA) infections. Spherical LDHNs with particle size, polydispersity index and zeta potential of 52.21±0.22 nm, 0.105±0.01, and -14.2±1.49 mV respectively were prepared by hot stirring and ultrasonication using Compritol 888 ATO, G4 PAMAM- succinamic acid dendrimer, and Kolliphor RH-40. Vancomycin encapsulation efficiency (%) in LDHNs was almost 4.5-fold greater than in lipid-polymer hybrid nanoparticles formulated using Eudragit RS 100. Differential scanning calorimetry and Fourier transform-infrared studies confirmed the formation of LDHNs. The interactions between the drug-dendrimer complex and lipid molecules using in silico modeling revealed the molecular mechanism behind the enhanced encapsulation and stability. Vancomycin was released from LDHNs over the period of 72 h with zero order kinetics and super case II transport mechanism. The minimum inhibitory concentration (MIC) against S. aureus and MRSA were 15.62 μg/ml and 7.81 μg/ml respectively. Formulation showed sustained activity with MIC of 62.5 μg/ml against S. aureus and 500 μg/ml against MRSA at the end of 72 and 54 h period respectively. The results suggest that the LDHN system can be an effective strategy to combat resistant infections.

Silver salts of carboxylic acid terminated generation 1 poly (propyl ether imine) (PETIM) dendron and dendrimers as antimicrobial agents against S. aureus and MRSA

Novel therapeutic strategies are essential to address the current global antimicrobial resistance crisis. Branched molecules with multiple peripheral functionalities, known as dendrimers, have gained interest as antimicrobials and have varying levels of toxicity. Silver displays activity against several micro-organisms only in its positively charged form. In this study, silver salts of generation 1 (G1) poly (propyl ether imine) (PETIM) dendron and dendrimers were synthesised and evaluated for their antimicrobial potential against sensitive and resistant bacteria. The purpose was to exploit the multiple peripheral functionalities of G1 PETIM dendron and dendrimers for the formation of silver salts containing multiple silver ions in a single molecule for enhanced antimicrobial activity at the lowest possible concentration. G1 PETIM dendron, dendrimers and their silver salts were synthesised and characterised by FT-IR, 1H NMR and 13C NMR. PETIM silver salts were evaluated against Hep G2, SKBR-3 and HT-29 cell lines for their cytotoxicity using the MTT assay. The G1 PETIM dendron/dendrimers, silver nitrate and silver salts of the G1 dendron (compound 13), G1 dendrimer with an aromatic core (compound 14) and an oxygen core (compound 15) were evaluated for activity against S. aureus and methicillin-resistant S. aureus (MRSA) by the broth dilution method. PETIM silver salts were found to be non-cytotoxic even up to 100 μg ml−1. Minimum inhibitory concentration values of compounds 13, 14 and 15 against S. aureus were 52.1, 41.7 and 20.8 μg ml−1 while against MRSA they were 125.0, 26.0 and 62.5 μg ml−1, respectively. The calculated fractional inhibitory concentration index further indicated that compound 14 specifically displayed additive effects against S. aureus and synergism against MRSA. The enhanced antimicrobial activities of the PETIM dendron/dendrimer-silver salts against both sensitive and resistant bacterial strains widen the pool of available pharmaceutical materials for optimizing treatment of bacterial infections.

Comparative buccal permeability enhancement of didanosine and tenofovir by potential multifunctional polymeric excipients and their effects on porcine buccal histology

Abstract This study identified and compared the buccal permeability properties of antiretroviral drugs, didanosine (ddI) and tenofovir (TNF), and the permeability effects of polymeric excipients – i.e. carboxymethylcellulose (CMC), sodium alginate (SA), polyacrylic acid (PAA) and polyethylene glycol (PEG) – as potential multifunctional excipients for buccal drug delivery. Permeation studies across porcine buccal mucosa were performed and the drug was quantified using UV spectrophotometry. The mean flux for both ddI (113–181 µg/cm2h) and TNF (40–102 µg/cm2h) increased linearly with increasing donor concentration. All polymeric excipients improved permeability of TNF while only PEG was effective for ddI. Permeability enhancement ratios at 20 mg/mL for ddI and TNF were 1.63 and 1.74, respectively, using PEG (0.5% w/v) and CMC (0.5% w/v), respectively. The maximum enhancement ratio of 2.13 for TNF was achieved with 4% w/v PEG. Light and transmission electron microscopy revealed no significant loss in cellular integrity of mucosa treated with either TNF or ddI alone or when coupled with PEG as a polymeric enhancer. Histomorphological observations correlated with flux values obtained for TNF and ddI alone, as well as with PEG’s effects on drug mass flux. TNF and ddI have demonstrated buccal delivery potential. Selective polymeric excipients provide an effective means to increase their penetration and may serve as potential formulation multifunctional excipients in a delivery system for delivery via the buccal route.

Novel dendritic derivatives of unsaturated fatty acids as promising transdermal permeation enhancers for tenofovir

This study was aimed at exploring the potential of unsaturated fatty acids (UFAs) [palmitoleic (PA), linoleic (LA), linolenic (LLA) and arachidonic acid (AA)], and their newly synthesized dendritic esters [PA1E, LA1E, LLA1E and AA1E] having basic tertiary nitrogen as the branching element as transdermal permeation enhancers for the delivery of tenofovir. The structures of the derivatives were confirmed by FTIR, NMR (1H and 13C) and HRMS. The in vitro cytotoxicity study revealed their biocompatibility. Amongst the UFAs, only PA and LLA exhibited transdermal enhancer potential [enhancement ratio (ER) of 1.35 and 2.9 respectively]. All synthesized derivatives at 1% w/w were found to be more effective enhancers as compared to their parent UFAs, with LLA1E being identified as the most superior (ER = 5.31). Further, the concentration effect study revealed that at 2% w/w LLA1E had a greater ER (6.11) as compared to its parent (ER = 3.85). The permeability data correlated with the observations made in the histomorphological and transepithelial electrical resistance (TEER) evaluations. There was no significant loss in the integrity of the epidermis, transcellular and intercellular route of transport across the epidermis, with drug and enhancer treatment having no permanent damage on the epidermis. The novel dendritic ester derivatives of the UFAs therefore can be considered as effective transdermal permeation enhancers.

High-energy ball milling of saquinavir increases permeability across the buccal mucosa

Abstract Saquinavir (SQV), a candidate for buccal drug delivery, is limited by poor solubility. This study identified the effects of high-energy ball milling on the buccal permeability of SQV and compared it to the effects of chemical enhancers, i.e. ethylenediaminetetraacetic acid (EDTA), sodium lauryl sulfate (SLS), polyethylene glycol (PEG) and beta cyclodextrin (β-cyclodextrin). SQV was ball milled using a high energy planetary mill (1, 3, 15 and 30 h) and permeation studies across porcine buccal mucosa were performed using franz diffusion cells. Drug was quantified by UV spectrophotometry. Both unmilled and milled SQV samples were able to permeate the buccal mucosa. Milled samples of 15 h displayed the greatest flux of 10.40 ± 1.24 µg/cm2 h and an enhancement ratio of 2.61. All enhancers were able to increase the buccal permeability of unmilled SQV, with SLS achieving the greatest flux (6.99 ± 0.7 µg/cm2) and an enhancement ratio of 1.75. However, all the milled SQV samples displayed greater permeability than SLS, the best chemical enhancer for unmilled SQV. Enhanced permeability by ball milling was attributed to reduction in particle size, formation of solid dispersions and an increase in solubility of milled samples. Microscopical evaluation revealed no significant loss in mucosal cellular integrity treated with either unmilled or milled SQV. Histological studies suggest that SQV uses both the paracellular and transcellular route of transport across the mucosa, with drug treatment having no permanent affects. High-energy ball milling was superior to the chemical enhancers studied for enhancement of SQV buccal permeation.

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.

Enhancing targeted antibiotic therapy via pH responsive solid lipid nanoparticles from an acid cleavable lipid

An acid cleavable lipid (SA-3M) was synthesized and used to develop pH-responsive solid lipid nanoparticles (SLNs) to deliver vancomycin base (VM-FB) to acidic infection sites. The size, polydispersity index and zeta potential of VM-FB_SA-3M_SLNs were 132.9±9.1nm, 0.159±0.01 and -26±4.4mV respectively, with 57.80±1.1% encapsulation efficiency. VM-FB release was significantly faster at pH6.5 than pH7.4. In vitro antibacterial activity against methicillin-susceptible and resistant Staphylococcus aureus (MSSA and MRSA) revealed that SLNs had enhanced activity at pH6.5 than pH7.4. In vivo study showed that the amount of MRSA remaining in the skin of VM-FB_SA-3M_SLNs treated mice was approximately 22-fold lower than VM-FB treated mice. Histological investigations revealed that signs of inflammation in the skin treated with VM-FB_SA-3M_SLNs were minimal. In conclusion, this study confirmed that SA-3M can form pH-responsive SLNs capable of releasing antibiotic specifically at acidic infection sites.