Saima Shabbir

Synthesis, morphology, and properties of self-assembled nanostructured aramid and polystyrene blends.

Aramid (Ar), produced from the reaction of aromatic diamines and diacid chloride, was reactively compatibilized with amino-functionalized polystyrene (APS) to explore blend morphology and interfacial cohesion. Two blend systems, Ar/PS and Ar/APS, were investigated over a range of pristine polystyrene (PS) or modified APS ratios. Morphology and thermal and mechanical properties were probed to evaluate the effect of amine units of APS on the compatibility with Ar. π-π stacking interactions in tandem with the random distribution of graft attachment locations and polydispersity of graft length in Ar-g-APS copolymer, aided merger of unreacted chains to drive molecular self-assembly process thus fortifying the nanostructured blends. Considerable augmentation of the blend morphology and thermal stability was achieved by incorporation of reactivity into Ar/APS system. A 20 wt % APS-containing blend was found to demonstrate optimum mechanical reinforcement, complemented by the optimal, thermal, and morphological profiles of the same blend. Future prospects are envisaged.

Metal distribution in Pakistani and foreign brands of cigarette tobacco.

No abstract available.

Polyionic hybrid nano-engineered systems comprising alginate and chitosan for antihypertensive therapeutics.

Hydrophobic nature of virtually all antihypertensive (AHT) drugs is the major hindrance towards their oral administration. Current study focuses on the development of polyionic hybrid nano drug delivery systems comprising sodium alginate and chitosan, loaded with distinct AHT drugs (captopril, amlodipine and valsartan). Encapsulation efficiency of hybrid NCS increased in the order of amlodipine>valsartan>captopril with average value of 42±0.9%, 91±1.5% and 96±1.9%, respectively. Scanning electron microscopy revealed hybrid NCS with smooth topography and round appearance in case of captopril. FTIR analysis confirmed the cross-linking between amino and carboxylate group of chitosan and alginate to form polyionic structures at nano-scale. Zeta-sizer experiments revealed that particle size distribution had increased from 197±12nm to 341±15nm for void and captopril loaded NCS. However, highly positive zeta potential of +32±1.6mV was not decreased significantly. In vitro sustained release assays reflected excellent retention of AHT drug in hybrid nanoparticles at 4°C and 37°C in physiological buffer, as less than 8% of the total drug was released in first 24h. Thus, carbohydrate-based hybrid NCS offering high loading capacity, stability and sustained release of hydrophobic drugs can be excellent alternative to current AHT therapeutics.

Polyelectrolyte Multicomponent Colloidosomes Loaded with Nisin Z for Enhanced Antimicrobial Activity against Foodborne Resistant Pathogens

Food grade micro- or nano-carrier systems (NCS) are being developed to improve the controlled release of antimicrobial agents. To augment the stability of liposomal NCS and to overcome the limitations associated with the use of free bacteriocin (nisin) in the food system, multi-component colloidosomes (MCCS) were developed by electrostatic interactions between anionic alginate and cationic chitosan (multilayer) around phospholipids based liposomes (core). Zeta-sizer results revealed the average diameter of 145 ± 2 nm, 596 ± 3 nm, and 643 ± 5 nm for nano-liposome (NL), chitosomes (chitosan coated NL) and MCCS, respectively. Zeta potential values of NCS varied from −4.37 ± 0.16 mV to 33.3 ± 6 mV, thus both chitosomes (CS) and MCCS were positively charged. Microstructure analysis by scanning electron microscope (SEM) revealed relatively higher size of MCCS with smooth and round morphology. TGA and DSC based experiments revealed that MCCS were thermally more stable than uncoated liposomes. Encapsulation efficiency of nisin in MCCS was observed to be 82.9 ± 4.1%, which was significantly higher than NL (56.5 ± 2.5%). FTIR analyses confirmed the cross-linking between sodium alginate and chitosan layer. Both qualitative (growth kinetics) and quantitative (colony forming unit) antimicrobial assays revealed that nisin loaded MCCS have superior potential to control resistant foodborne pathogens including Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis, (5.8, 5.4, and 6.1 Log CFUmL−1 reduction, respectively) as compared to free nisin, loaded NL or CS. Controlled release kinetics data fitted with Korsmeyer–Peppas model suggested that nisin release from MCCS followed Fickian diffusion. Cytotoxic studies on human blood cells and HepG2 cell lines revealed hemocompatibility and non-toxicity of MCCS. Thus, due to enhanced controlled release, stability and biocompatibility; these multi-component colloidosomes can be useful for incorporating antimicrobial agents into functional foods, beverages and pharmaceutical products to combat pathogenic and spoilage bacteria.