Suresh B. Vepuri

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.

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.

Adenosine Monophosphate-Activated Protein Kinase (AMPK) as a Diverse Therapeutic Target: A Computational Perspective.

AbstractAdenosine monophosphate-activated protein kinase (AMPK) is viewed as a privileged therapeutic target for several diseases such as cancer, diabetes, inflammation, obesity, etc. In addition, AMPK has entered the limelight of current drug discovery with its evolution as a key metabolic regulator. AMPK also plays a key role in the maintenance of cellular energy homeostasis. Structurally, AMPK is a heterotrimeric protein, which consists of three protein subunits (α, β, and γ). The crystal structure of AMPK was solved, and several computational studies including homology modeling, molecular docking, molecular dynamics, and QSAR have been reported in order to explore the structure and function of this diverse therapeutic target. In this review, we present a comprehensive up-to-date overview on the computational and molecular modeling approaches that have been carried out on AMPK in order to understand its structure, function, dynamics, and its drug binding landscape. Information provided in this review would be of great interest to a wide pool of researchers involved in the design of new molecules against various diseases where AMPK plays a predominant role. Graphical Abstractᅟ

An unexplored remarkable PNIPAM-osmolyte interaction study: An integrated experimental and simulation approach

We investigate the aggregation and collapse of water soluble amphiphilic polymer, poly(N-isopropylacrylamide) (PNIPAM), in aqueous solution containing variable amount of trehalose, sucrose and sorbitol. The effect of these osmolytes on the coil to globular transition of the PNIPAM is studied by the use of comprehensive biophysical techniques like UV-visible spectroscopy, fluorescence spectroscopy, dynamic light scattering and Fourier transform infrared spectroscopy (FTIR). The polarization induced by these additives promotes the collapsed state of PNIPAM at much lower temperature as compared to the pure PNIPAM in aqueous solution. The decrease in the lower critical solution temperature (LCST) of the polymer with increase in the concentration of osmolyte is due to the significant changes in the interactions among polymer, osmolyte and water. The high affinity of these additives toward water destabilize the hydrated macromolecular structure via preferential interactions. To investigate the molecular mechanism behind the decrease in the LCST of the polymer in presence of the osmolytes, a molecular dynamics (MD) study was performed. The MD simulation has clearly shown the reduction in hydration shell of the polymer after interacting with the osmolyte. MD study revealed significant changes in polymer conformation because of osmolyte interaction and strongly supports the experimental observation of polymer phase transition at temperature lower than typical LCST. The driving force for concomitant sharp configurational transition has been attributed to the rupture of hydrogen bonds between water and polymer and to the hydrophobic association of the polymer. The results of the present study can be used in the bioresponsive smart PNIPAM-based devices as its LCST is close to body temperature. This study provides an alternative method to tune the LCST of the widely accepted model PNIPAM polymer.

Nicotinaldehyde [2,8-bis-(trifluoro-meth-yl)quinolin-4-yl]hydrazone monohydrate.

In the title compound, C17H10F6N4·H2O, the pyridine ring is not coplanar with the quinoline ring system; the dihedral angle between the two planes is 21.3 (1)°. One of the trifluoromethyl group is disordered over two orientations with occupancies of 0.70 (1) and 0.30 (1). The water molecule is disordered over two positions with occupancies of 0.76 (1) and 0.24 (1). In the crystal, the water molecule is linked to the main molecule via N—H⋯O and C—H⋯O hydrogen bonds, and inversion-related pairs are linked via O—H⋯N hydrogen bonds. In addition, a weak π–π interaction is observed between the pyridine ring and the pyridine ring of the quinoline unit, with a centroid–centroid distance of 3.650 (2) Å.

Comprehensive Computational and Experimental Analysis of Biomaterial toward the Behavior of Imidazolium-Based Ionic Liquids: An Interplay between Hydrophilic and Hydrophobic Interactions

To provide insights into the aggregation behavior, hydration tendency and variation in phase transition temperature produced by the addition of ionic liquids (ILs) to poly(N-isopropylacrylamide) (PNIPAM) aqueous solution, systematic physicochemical studies, and molecular dynamic simulations were carried out. The influence of ILs possessing the same [Cl]- anion and a set of cations [Cnmim]+ with increasing alkyl chain length such as 1-ethyl-3-methylimidazolium ([Emim]+), 1-allyl-3-methylimidazolium ([Amim]+), 1-butyl-3-methylimidazolium ([Bmim]+), 1-hexyl-3-methylimidazolium ([Hmim]+), 1-benzyl-3-methylimidazolium ([Bzmim]+), and 1-decyl-3-methylimidazolium ([Dmim]+) on the phase transition of PNIPAM was monitored by the aid of UV-visible absorption spectra, fluorescence intensity spectra, viscosity (η), dynamic light scattering (DLS), and Fourier transform infrared (FTIR) spectroscopy. Furthermore, to interpret the direct images and surface morphologies of the PNIPAM-IL aggregates, we performed field emission scanning electron microscopy (FESEM). The overall specific ranking of ILs in preserving the hydration layer around the PNIPAM aqueous solution was [Emim][Cl] > [Amim][Cl] > [Bmim][Cl] > [Hmim][Cl] > [Bzmim][Cl] > [Dmim][Cl]. Moreover, to investigate the molecular mechanism behind the change in the lower critical solution temperature (LCST) of the polymer in the presence of the ILs, a molecular dynamics (MD) study was performed. The MD simulation has clearly shown the reduction in hydration shell of the polymer after interacting with the ILs at their respective LCST. MD study revealed significant changes in polymer conformation because of IL interactions and strongly supports the experimental observation of polymer phase transition at a temperature lower than typical LCST for all the studied ILs. The driving force for concomitant sharp configurational transition has been attributed to the displacement of water molecules on the polymer surface by the ILs because of their hydrophobic interaction with the polymer.

(2E)-1-(5-Bromothiophen-2-yl)-3-(4-chloro-phen-yl)prop-2-en-1-one.

In the title compound, C13H8BrClOS, the thiophene and phenyl rings are inclined by 40.69 (11)° to each other. The crystal structure is characterized by C—H⋯π interactions, which link the molecules into broad layers parallel to (100). Short Br⋯Cl contacts [3.698 (1) Å] link these layers along [100].

(2E)-3-(2-Bromo­phen­yl)-1-(5-bromo­thio­phen-2-yl)prop-2-en-1-one

The asymmetric unit of the title compound, C13H8Br2OS, contains two molecules, in which the dihedral angles between the thiophene and benzene rings are 10.5 (3) and 33.2 (4)°. There are no significant directional interactions in the crystal.

(E)-1-(5-Bromo­thio­phen-2-yl)-3-(3,4,5-trimeth­oxy­phen­yl)prop-2-en-1-one

In the title compound, C16H15BrO4S, the dihedral angle between the thiophene and benzene rings is 13.08 (16)°. The C atoms of the meta methoxy groups of the substituted benzene ring lie close to the plane of the ring [displacements = 0.049 (5) and −0.022 (4) Å], whereas the para-C atom is significantly displaced [−1.052 (4) Å]. In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds, forming C(11) chains propagating in [100].

Polyelectrolyte complex of vancomycin as a nanoantibiotic: Preparation, in vitro and in silico studies.

Delivery of antibiotics by various nanosized carriers is proving to be a promising strategy to combat limitations associated with conventional dosage forms and the ever-increasing drug resistance problem. This method entails improving the pharmacokinetic parameters for accumulation at the target infection site and reducing their adverse effects. It has been proposed that antibiotic nanoparticles themselves are more effective delivery system than encapsulating the antibiotic in a nanosystem. In this study, we report on nanoparticles of vancomycin (VCM) by self-assembled amphiphilic-polyelectrolyte complexation between VCM hydrochloride and polyacrylic acid sodium (PAA). The size, polydispersity index and zeta potential of the developed nanoplexes were 229.7 ± 47.76 nm, 0.442 ± 0.075, -30.4 ± 5.3 mV respectively, whereas complexation efficiency, drug loading and percentage yield were 75.22 ± 1.02%, 58.40 ± 1.03% and 60.60 ± 2.62% respectively. An in vitro cytotoxicity study on three mammalian cell lines using MTT assays confirmed the biosafety of the newly formulated nanoplexes. Morphological investigations using scanning electron microscope showed cube shaped hexagonal-like particles. In vitro drug release studies revealed that the drug was completely released from the nanoplexes within 12h. In silico studies revealed that the nano-aggregation was facilitated by means of self-association of VCM in the presence of the polymer. The supramolecular pattern of the drug self-association was found to be similar to that of the VCM dimer observed in the crystal structure of the VCM available in Protein Data Bank. In vitro antibacterial activity against susceptible and resistant Staphylococcus aureus proved that the potency of VCM was retained after being formulated as the nanoplex. In conclusion, VCM nanoplexes could be a promising nanodrug delivery system to treat infections of S. aureus origin.