Antimicrobial Property of Silver Nanoparticles: Effects of Concentration and Temperature on Bacterial Isolates

Importance of hospital environment in patient-care has been recognized widely in infection prevention and control. Inappropriate antibiotic use led to emergence of resistant strains that are difficult to treat with the available antibiotics. Progress in nanotechnology led to enhancement of nanoparticles with physicochemical characteristics and functionality that overcomes the constraints of common antimicrobials. Aim was to investigate effective antimicrobial role of Silver nanoparticle (Ag-NPs) against clinically important bacterial strains and observe effects of varying storage temperatures on Ag-NPs antimicrobial activity. Different concentrations of Ag-NPs were tested against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Acinetobacter baumannii using diffusion method. Zone of inhibition (ZOI) for each organism was directly proportional to concentration of Ag-NPs used. Mean ZOI values at different concentrations were significantly different for all organisms with p-value <0.001 for E. coli, S. aureus, P. aeruginosa and 0.004 for A. baumannii. Variation in storage temperature hardly showed any effects on the antimicrobial property of the Ag-NPs. Scanning electron microscopy (SEM) showed morphological and size variations in Ag-NPs exposed cells when compared to control strains, especially for S. aureus, E. coli and P. aeruginosa. Damaged cell membrane areas can be clearly distinguished in E. coli and P. aeruginosa thus suggesting bacterial membrane disruption. These finding can help design a larger study where Ag-NPs can be used in various medical instruments which are usually kept at room temperatures. Also, outcomes of this study may help in designing proper implants, prosthesis and equipment coated with minimum concentration of nanoparticles that might be considered safe for medical applications

Effect of Storage Time and Temperature on Digestibility, Thermal, and Rheological Properties of Retrograded Rice

Retrogradation is defined as the recrystallization or realignment of amylose and amylopectin chains upon cooling of gelatinization starch gels. The storage conditions such as the storage time and temperature are crucial factors that influence and govern the degree of retrogradation and in turn, affect the formation of resistant starch and alteration of thermal and rheological properties. This article investigates the effect of storage time and temperature on the properties of retrograded rice starch. Rice kernels of five different indigenous varieties, namely Diasang lahi, Khaju lahi, Dhusuri bao, Omkar, and Bili rajamudi were cooked by boiling in water and stored at 4 °C and −20 °C for 6 and 12 h, respectively. Differential scanning calorimetry (DSC) studies revealed in raw form that Bili rajamudi exhibited the highest peak gelatinization temperature (Tp, °C) at 79.05 °C whereas Diasang lahi showed the least Tp at 56.12 °C. Further, it was indicated that the Tp and degree of retrogradation (DR%) also increase with increasing time and decreasing temperature of storage. All samples stored at −20 °C for 12 h exhibited the highest degree of retrogradation DR%. Amongst all five varieties stored at −20 °C for 12 h, Omkar exhibited the highest %DR, followed by Bili rajamudi, Khaju lahi, Dhusuri bao, and Diasang lahi. A negative correlation was also established between Tp and resistant starch content (RS%). It was also observed that the resistant starch (RS%) content increased with the increasing time and decreasing temperature of storage. A strong negative correlation was observed between RS% and non-resistant starch (NRS%). Further, rheological studies indicated that retrogradation also affects the viscosity and dynamic rheological properties of starch. In this study, it was evident that extending storage duration from 6 to 12 h and lowering temperature from 4 to −20 °C impact retrogradation of rice starch, which in turn affects the starch’s gelatinization, digestibility, and rheology. Rice starch retrograded at lower temperatures for a longer period could prove to be extremely beneficial for development of food products with better textural properties and high RS content or low glycemic index

Comparison of conventional drilling and helical milling for hole making in Ti6Al4V titanium alloy under sustainable dry condition

Hole drilling in Ti6Al4V titanium alloy is challenging due to its poor machinability resulting from high-temperature strength and low thermal conductivity. Therefore, an evaluation of the helical milling process is carried out by comparing the thrust force, surface roughness, machining temperature, burr size, and hole diametrical accuracy with the conventional drilling process. The results indicate the advantage of the helical milling in terms of the lower magnitude of thrust force. The holes generated using helical milling displayed a superior surface finish at lower axial feed conditions, while higher axial feed conditions result in chatter due to the tool deformation. Also, the absence of a heat-affected zone (HAZ) under dry helical milling conditions indicates the work surface formation without thermal damage. Besides, a significant reduction in the size of the burrs is noted during helical milling due to lower machining temperature. Analysis of the hole diameter reinforces the capability of the helical milling process for processing H7 quality holes. Consequently, helical milling can be considered a sustainable alternative to mechanical drilling, considering its ability to machine quality holes under dry machining conditions

Nosocomial Infections and Role of Nanotechnology

Nosocomial infections, termed hospital-acquired infections (HAIs), are acquired from a healthcare or hospital setting. HAI is mainly caused by bacteria, such as Acinetobacter baumannii, Klebsiella pneumoniae, Escherichia coli, Enterococci spp., Methicillin-resistant Staphylococcus aureus (MRSA), and many more. Due to growing antibacterial resistance, nanotechnology has paved the way for more potent and sensitive methods of detecting and treating bacterial infections. Nanoparticles have been used with molecular beacons for identifying bactericidal activities, targeting drug delivery, and anti-fouling coatings, etc. This review addresses the looming threat of nosocomial infections, with a focus on the Indian scenario, and major initiatives taken by medical bodies and hospitals in spreading awareness and training. Further, this review focuses on the potential role nanotechnology can play in combating the spread of these infections

Fostering Κ-carrageenan Hydrogels with the Power of Natural Crosslinkers: A Comparison between Tender Coconut Water and Potassium Chloride for Antibacterial Therapy

Hydrogels have emerged as a promising solution to combat infections in various biomedical applications by acting as antibacterial drug carriers, but they lack mechanical strength and must be crosslinked before use. Herein, we investigated whether tender coconut water can be used as a natural alternative to KCl to crosslink κ-carrageenan hydrogels for antibacterial therapy. Κ-carrageenan hydrogels crosslinked with tender coconut water, KCl, and their combination were fabricated, and their morphology, chemical bonding, compressive strength, water uptake capacity, degradation resistance, and cytotoxicity were assessed. The results showed that crosslinking with tender coconut water and KCl increased the compressive strength of κ-carrageenan hydrogels by 450%, rendered an excellent water retention capacity, and degraded by just about 5% after 20 days! The scanning electron micrographs show that crosslinking with tender coconut water and KCl compacted the hydrogel morphology with narrow cracks for efficient diffusion, and such were biocompatible when tested against 3T3 cells. The infrared analysis confirmed that diclofenac sodium remained inert when introduced into the hydrogel matrices. Also, the in-vitro release behavior and antibacterial activity of the hydrogels were assessed by loading them with diclofenac sodium nanoemulsified to increase hydrophilicity, in which the release of the hydrogels crosslinked with tender coconut water and KCl was steady and sustained. Such hydrogels also showed a unique antibacterial activity against Staphylococcus aureus and Escherichia coli, with the latter much more prominent than the former. These results confirm that crosslinking with tender coconut water and KCl is a superior alternative to KCl for κ-carrageenan hydrogels