Stages That Lead to Drop Depinning and Onset of Motion.

In this paper, we consider drops that are subjected to a gradually increasing lateral force and follow the stages of the motion of the drops. We show that the first time a drop slides as a whole is when the receding edge of the drop is pulled by the advancing edge (the advancing edge drags the receding edge). The generality of this phenomenon includes sessile and pendant drops and spans over various chemically and topographically different cases. Because this observation is true for both pendant and sessile cases, we exclude hydrostatic pressure as its reason. Instead, we explain it in terms of the wetting adaptation and interfacial modulus, that is, the difference in the energies of the solid interface at the advancing and receding edges. At the receding edge, a slight motion exposes to the air a recently wetted solid surface whose molecules had reoriented to the liquid and will take time to reorient back to the air. This results in a high surface energy at the solid-air interface which pulls on the triple line, that is, inhibits the motion of the receding edge. On the other hand, at the advancing edge, a slight advancement does not change the nature of the solid interfacial molecules outside the drop, and the advancing side's sliding can continue. Moreover, the solid molecules under the drop at the advancing edge take time to reorient, and hence, their configuration is not yet adapted for the liquid and therefore not adapted for retention of the advancing edge. Therefore, in sliding-drop experiments, the advancing edge moves before the receding one, typically a few times before the receding edge moves. For the same reason, the last motion of the receding edge usually happens as a result of the advancing edge pulling on it.

Prospects and application of nanobiotechnology in food preservation: molecular perspectives.

Applications of biotechnological tools in food preservation have shown promising results in minimizing food spoilage. Design and development of highly efficient food preservatives are one of the key success factors in this application field. However, due to the inherent shortcomings of the bulk forms of such preservatives, research was in progress to find suitable alternatives to replace conventional modalities. The intervention of nanotechnology has made this approach feasible in almost every aspect of food preservation. This interface domain of nanobiotechnology has been very well explored in the last few decades and vast literature has been reported. Researchers have developed efficient nanopreservatives (NPRs) for diverse applications. However, the literature available on nano-based food preservation is not inclusive of molecular perspectives involved in food preservation. There is a large knowledge gap in the interface domain concerning the physics of intermolecular and interfacial forces and nanotechnology which play decisive roles in designing edible coatings (ECs). There is an urgent need for identifying the nano and molecular level contributing factors for developing efficient NPRs. Moreover, it is imperative to understand the possible health impact of NPRs in public interest and concern. This review revisits the fundamental aspects of food preservation and navigates through the applicability, safety, molecular aspects and future direction of NPRs.

The Influence of Gravity on Contact Angle and Circumference of Sessile and Pendant Drops has a Crucial Historic Aspect.

Normally, pendant drops adapt contact angles that are closer to 90° than their sessile analogues. This is due to the drop's weight that pulls the pendant drop and straightens its contact angles. In this paper, we show a case in which the opposite happens: sessile drops that adapt contact angles that are closer to 90° than their pendant analogues. To achieve these peculiar states, one needs to increase the effective gravity on the drops and then relax it again to 1 g. Apparently, this and other phenomena depend not only on the direction of the gravitational force but also on the drop's history. We show that the drop's contact angle (and resultant area) is affected by two types of histories: short-term history and long-term history. For example, if we gradually increase the effective gravity on the drop, decrease it back to 1 g, and then repeat this cycle again and again, we see that the first cycle is drastically different, whereas other cycles approach a plateau in their behavior. In addition to drop's history, we explain these observations in terms of volume conservation, drop contact area, and pinning effect. This study may be generalized for other body forces such as electrical and magnetic or accelerating systems.

Droplets Sliding down a Vertical Surface under Increasing Horizontal Forces.

We have investigated the retention forces of liquid drops on rotating, vertical surfaces. We considered two scenarios: in one, a horizontal, centrifugal force pushes the drop toward the surface (?pushed drop? case), and in the other, a horizontal, centrifugal force pulls the drop away from the surface (?pulled drop? case). Both drops slide down as the centrifugal force increases, although one expects that the pushed drop should remain stuck to the surface. Even more surprising, when the centrifugal force is low, the pushed drop moves faster than the pulled drop, but when the centrifugal force is high, the pushed drop moves much slower than the pulled drop. We explain these results in terms of interfacial modulus between the drop and the surface.

Alternatives to antibiotics in poultry feed: molecular perspectives.

The discovery of the growth promoting property of antibiotics led to their use as antibiotic feed additives (AFAs) in animal feed at sub-therapeutic doses. Although this has been beneficial for animal health and productivity, it has been, essentially, a double-edged sword. The continued and non-judicious use of AFAs has led to the selection and dissemination of antibiotic-resistant strains of poultry pathogens such as Salmonella, Campylobacter and Escherichia coli. The rapid spread of drug-resistant pathogens as well as emergence of antibiotic-related environmental pollutants is of global concern. Hence, the identification and development of new and effective alternatives to antibiotics that do not hinder productivity is imperative. For this, it is essential to understand not only the molecular basis of development of resistance to AFAs but also the mechanisms of action of AFA alternatives and how they differ from AFAs. This review provides a molecular perspective on the alternatives to antibiotics that have been proposed till date and their current trends, as well as novel approaches such as development of improved delivery systems.

Why Drops Bounce on Smooth Surfaces.

It is shown that introducing gravity in the energy minimization of drops on surfaces results in different expressions when minimized with respect to volume or with respect to contact angle. This phenomenon correlates with the probability of drops to bounce on smooth surfaces on which they otherwise form a very small contact angle or wet them completely. Theoretically, none of the two minima is stable: the drop should oscillate from one minimum to the other as long as no other force or friction will dissipate the energy. Experimentally, smooth surfaces indeed show drops that bounce on them. In some cases, they bounce after touching the solid surface, and in some cases they bounce from a nanometric air, or vacuum film. The bouncing energy can be stored in the interfaces: liquid-air, liquid-solid, and solid-air. The lack of a single energy minimum prevents a simple convergence of the drop's shape on the solid surface, and supports its bouncing back to the air. Therefore, the lack of a simple minimum described here supports drop bouncing on hydrophilic surfaces such as that reported by Kolinski et al. Our calculation shows that the smaller the surface tension, the bigger the difference between the contact angles calculated based on the two minima. This agrees with experimental finding where reducing the surface tension, for example, by adding surfactants, increases the probability for bouncing of the drops on smooth surfaces.

Solid-Liquid Work of Adhesion.

We establish a tool for direct measurements of the work needed to separate a liquid from a solid. This method mimics a pendant drop that is subjected to a gravitational force that is slowly increasing until the solid-liquid contact area starts to shrink spontaneously. The work of separation is then calculated in analogy to Tate's law. The values obtained for the work of separation are independent of drop size and are in agreement with Dupré's theory, showing that they are equal to the work of adhesion.

A review on the important aspects of lipase immobilization on nanomaterials.

Lipase is one of the most widely used enzymes and plays an important role in biotechnological and industrial processes including food, paper, and oleochemical industries, as well as in pharmaceutical applications. However, its aqueous solubility and instability make its application relatively difficult and expensive. The immobilization technique is often used to improve lipase performance, and the strategy has turned out to be a promising method. Immobilized lipase on nanomaterials (NMs) has shown superiority to the free lipase, such as improved thermal and pH stability, longer stable time, and the capacity of being reused. However, immobilization of lipase on NMs also sometimes causes activity loss and protein loading is relatively lowered under some conditions. The overall performance of immobilized lipase on NMs is influenced by mechanisms of immobilization, type of NMs being used, and physicochemical features of the used NMs (such as particle size, aggregation behavior, NM dimension, and type of coupling/modifying agents being used). Based on the specific features of lipase and NMs, this review discusses the recent developments, some mechanisms, and influence of NMs on lipase immobilization and their activity. Multiple application potential of the immobilized lipases has also been considered.

The microbial growth potential of antiscalants used in seawater desalination.

20 years since the first report on the biofouling potential of chemicals used for scale control, still, antiscalants with high bacterial growth potential are used in practice. Evaluating the bacterial growth potential of commercially available antiscalants is therefore essential for a rational selection of these chemicals. Previous antiscalant growth potential tests were conducted in drinking water or seawater inoculated with model bacterial species which do not represent natural bacterial communities. To reflect better on the conditions of desalination systems, we investigated the bacterial growth potential of eight different antiscalants in natural seawater and an autochthonous bacterial population as inoculum. The antiscalants differed strongly in their bacterial growth potential varying from ≤ 1 to 6 µg easily biodegradable C equivalents/mg antiscalant. The six phosphonate-based antiscalants investigated showed a broad range of growth potential, which depended on their chemical composition, whilst the biopolymer and the synthetic carboxylated polymers-based antiscalants showed limited or no significant bacterial growth. Moreover, nuclear magnetic resonance (NMR) scans enabled antiscalant fingerprinting, identifying components and contaminants, providing a rapid and sensitive characterization, and opening opportunities for rational selection of antiscalants for biofouling control.

Seawater Reverse Osmosis Performance Decline Caused by Short-Term Elevated Feed Water Temperature.

The shortage of fresh water resources has made the desalination of seawater a widely adopted technology. Seawater reverse osmosis (SWRO) is the most commonly used method for desalination. The SWRO process is energy-intensive, and most of the energy in SWRO is spent on pressurizing the seawater to overcome the osmotic barrier for producing fresh water. The pressure needed depends on the salinity of the seawater, its temperature, and the membrane surface properties. Membrane compaction occurs in SWRO due to hydraulic pressure application for long-term operations and operating temperature fluctuations due to seasonal seawater changes. This study investigates the effects of short-term feed water temperature increase on the SWRO process in a full-scale pilot with pretreatment and a SWRO installation consisting of a pressure vessel which contains seven industrial-scale 8" diameter spiral wound membrane elements. A SWRO feed water temperature of 40 °C, even for a short period of 7 days, caused a permanent performance decline illustrated by a strong specific energy consumption increase of 7.5%. This study highlights the need for membrane manufacturer data that account for the water temperature effect on membrane performance over a broad temperature range. There is a need to develop new membranes that are more tolerant to temperature fluctuations.

Green synthesis of gold nanoparticles using Nyctanthes arbortristis flower extract.

The present study explores the reducing and capping potentials of ethanolic flower extract of the plant Nyctanthes arbortristis for the synthesis of gold nanoparticles. The extract at different volume fractions were stirred with HAuCl4 aqueous solution at 80 °C for 30 min. The UV-Vis spectroscopic analysis of the reaction products confirmed successful reduction of Au(3+) ions to gold nanoparticles. Transmission electron microscope (TEM) revealed dominant spherical morphology of the gold nanoparticles with an average diameter of 19.8 ± 5.0 nm. X-ray diffraction (XRD) study confirmed crystalline nature of the synthesized particles. Fourier transform infra-red (FTIR) and nuclear magnetic resonance (NMR) analysis of the purified and lyophilized gold nanoparticles confirmed the surface adsorption of biomolecules during preparation and caused long-term (6 months) stability. Low reaction temperature (25 °C) favored anisotropy. The strong reducing power of the flower extract can also be tested in the green synthesis of other metallic nanoparticles.

Science-society-policy interface for microplastic and nanoplastic: Environmental and biomedical aspects.

The global concern over the possible consequences of the downsizing of plastic to microplastics (MPs) and nano plastics (NPs) needs to be addressed with a new conceptual framework. The transformation of plastics to MPs and NPs can be discussed in terms of fundamental physics principles applicable to micro and nanophase matter and colloidal science principles. Further, accurate and reliable detection and characterization of MPs and NPs are crucial for an extensive understanding of their environmental and ecological impacts. The other decisive factor that can classify MPs and NPs as hazardous to existing nanomaterials is discussing the cytotoxicity study on human cell lines. The human health risk assessment that might arise from the ingestion of MPs and NPs can be addressed about contrast agents used for medical imaging. However, the lack of standard analytical techniques for MPs and NPs measurement is an emerging challenge for analytical scientists due to their complex physicochemical properties, especially in environmental samples. This review article navigates readers through the point of origin of MPs and NPs and their interdisciplinary aspects. Biomedical applications of plastics and concerns over the toxicity of MPs and NPs are further analyzed. Moreover, the analytical challenges of MPs and NPs have been discussed with critical inputs. Finally, the worldwide efforts being made for creating a common platform of discussion on a different aspect of plastic pollution were taken into account.

Encapsulation of curcumin in alginate-chitosan-pluronic composite nanoparticles for delivery to cancer cells.

We report a nanoformulation of curcumin with a tripolymeric composite for delivery to cancer cells. The composite nanoparticles (NPs) were prepared by using three biocompatible polymers-alginate (ALG), chitosan (CS), and pluronic-by ionotropic pre-gelation followed by polycationic cross-linking. Pluronic F127 was used to enhance the solubility of curcumin in the ALG-CS NPs. Atomic force and scanning electron microscopic analysis showed that the particles were nearly spherical in shape with an average size of 100 +/- 20 nm. Fourier transform-infrared analysis revealed potential interactions among the constituents in the composite NPs. Encapsulation efficiency (%) of curcumin in composite NPs showed considerable increase over ALG-CS NPs without pluronic. The in vitro drug release profile along with release kinetics and mechanism from the composite NPs were studied under simulated physiological conditions for different incubation periods. A cytotoxicity assay showed that composite NPs at a concentration of 500 microg/mL were nontoxic to HeLa cells. Cellular internalization of curcumin-loaded composite NPs was confirmed from green fluorescence inside the HeLa cells. The half-maximal inhibitory concentrations for free curcumin and encapsulated curcumin were found to be 13.28 and 14.34 muM, respectively. FROM THE CLINICAL EDITOR: A nanoformulation of curcumin with a tri-component polymeric composite for delivery to cancer cells is reported in this paper. Cellular internalization of curcumin loaded composite nanoparticles was confirmed from green fluorescence inside the HeLa cells.

Biomimetic Coating-free Superomniphobicity.

Superomniphobic surfaces, which repel droplets of  polar and apolar liquids, are used for reducing frictional drag, packaging electronics and foods, and separation processes, among other applications. These surfaces exploit perfluorocarbons that are expensive, vulnurable to physical damage, and have a long persistence in the environment. Thus, new approaches for achieving superomniphobicity from common materials are desirable. In this context, microtextures comprising "mushroom-shaped" doubly reentrant pillars (DRPs) have been shown to repel drops of polar and apolar liquids in air irrespective of the surface make-up. However, it was recently demonstrated that DRPs get instantaneously infiltrated by the same liquids on submersion because while they can robustly prevent liquid imbibition from the top, they are vulnerable to lateral imbibition. Here, we remedy this weakness through bio-inspiration derived from cuticles of Dicyrtomina ornata, soil-dwelling bugs, that contain cuboidal secondary granules with mushroom-shaped caps on each face. Towards a proof-of-concept demonstration, we created a perimeter of biomimicking pillars around arrays of DRPs using a two-photon polymerization technique; another variation of this design with a short wall passing below the side caps was investigated. The resulting gas-entrapping microtextured surfaces (GEMS) robustly entrap air on submersion in wetting liquids, while also exhibiting superomniphobicity in air. To our knowledge, this is the first-ever microtexture that confers upon intrinsically wetting materials the ability to simultaneously exhibit superomniphobicity in air and robust entrapment of air on submersion. These findings should advance the rational design of coating-free surfaces that exhibit ultra-repellence (or superomniphobicity) towards liquids.

Proof-of-Concept for Gas-Entrapping Membranes Derived from Water-Loving SiO2/Si/SiO2 Wafers for Green Desalination.

Desalination through direct contact membrane distillation (DCMD) exploits water-repellent membranes to robustly separate counterflowing streams of hot and salty seawater from cold and pure water, thus allowing only pure water vapor to pass through. To achieve this feat, commercial DCMD membranes are derived from or coated with water-repellent perfluorocarbons such as polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF). However, the use of perfluorocarbons is limiting due to their high cost, non-biodegradability, and vulnerability to harsh operational conditions. Unveiled here is a new class of membranes referred to as gas-entrapping membranes (GEMs) that can robustly entrap air upon immersion in water. GEMs achieve this function by their microstructure rather than their chemical make-up. This work demonstrates a proof-of-concept for GEMs using intrinsically wetting SiO2/Si/SiO2 wafers as the model system; the contact angle of water on SiO2 is θo ≈ 40°. Silica-GEMs had 300 µm-long cylindrical pores whose diameters at the (2 µm-long) inlet and outlet regions were significantly smaller; this geometrically discontinuous structure, with 90° turns at the inlets and outlets, is known as the "reentrant microtexture". The microfabrication protocol for silica-GEMs entails designing, photolithography, chrome sputtering, and isotropic and anisotropic etching. Despite the water loving nature of silica, water does not intrude silica-GEMs on submersion. In fact, they robustly entrap air underwater and keep it intact even after six weeks (>106 seconds). On the other hand, silica membranes with simple cylindrical pores spontaneously imbibe water (< 1 s). These findings highlight the potential of the GEMs architecture for separation processes. While the choice of SiO2/Si/SiO2 wafers for GEMs is limited to demonstrating the proof-of-concept, it is expected that the protocols and concepts presented here will advance the rational design of scalable GEMs using inexpensive common materials for desalination and beyond.

Rendering SiO2/Si Surfaces Omniphobic by Carving Gas-Entrapping Microtextures Comprising Reentrant and Doubly Reentrant Cavities or Pillars.

We present microfabrication protocols for rendering intrinsically wetting materials repellent to liquids (omniphobic) by creating gas-entrapping microtextures (GEMs) on them comprising cavities and pillars with reentrant and doubly reentrant features. Specifically, we use SiO2/Si as the model system and share protocols for two-dimensional (2D) designing, photolithography, isotropic/anisotropic etching techniques, thermal oxide growth, piranha cleaning, and storage towards achieving those microtextures. Even though the conventional wisdom indicates that roughening intrinsically wetting surfaces (θo < 90°) renders them even more wetting (θr < θo < 90°), GEMs demonstrate liquid repellence despite the intrinsic wettability of the substrate. For instance, despite the intrinsic wettability of silica θo ≈ 40° for the water/air system, and θo ≈ 20° for the hexadecane/air system, GEMs comprising cavities entrap air robustly on immersion in those liquids, and the apparent contact angles for the droplets are θr > 90°. The reentrant and doubly reentrant features in the GEMs stabilize the intruding liquid meniscus thereby trapping the liquid-solid-vapor system in metastable air-filled states (Cassie states) and delaying wetting transitions to the thermodynamically-stable fully-filled state (Wenzel state) by, for instance, hours to months. Similarly, SiO2/Si surfaces with arrays of reentrant and doubly reentrant micropillars demonstrate extremely high contact angles (θr ≈ 150°-160°) and low contact angle hysteresis for the probe liquids, thus characterized as superomniphobic. However, on immersion in the same liquids, those surfaces dramatically lose their superomniphobicity and get fully-filled within <1 s. To address this challenge, we present protocols for hybrid designs that comprise arrays of doubly reentrant pillars surrounded by walls with doubly reentrant profiles. Indeed, hybrid microtextures entrap air on immersion in the probe liquids. To summarize, the protocols described here should enable the investigation of GEMs in the context of achieving omniphobicity without chemical coatings, such as perfluorocarbons, which might unlock the scope of inexpensive common materials for applications as omniphobic materials. Silica microtextures could also serve as templates for soft materials.

Dataset on the synthesis and physicochemical characterization of blank and curcumin encapsulated sericin nanoparticles obtained from Philosamia ricini silkworm cocoons.

The dataset presents the synthesis and physicochemical characterization of blank and curcumin encapsulated sericin protein nanoparticles obtained from Philosamia ricini (also known as Ahimsa silk or Peace silk or Eri). Reports on application of sericin protein obtained from P. ricini are scanty at best. Sericin was extracted from the cocoons by high temperature and high pressure method. Synthesis of sericin nanoparticles was carried out by desolvation method using acetone as the desolvating agent. Curcumin was used as a hydrophobic model drug and was encapsulated into the sericin nanoparticles. Physicochemical characterization of the blank and curcumin encapsulated sericin nanoparticles were carried out by different instrumental analyses. The size and surface charges of sericin nanoparticles changed with the variation of applied sericin concentration. Encapsulation efficiency and loading capacity of the encapsulated sericin nanoparticles showed variation with curcumin concentration. The obtained data indicated the applicative potentials of sericin protein extracted from Philosamia ricini silkworm cocoons.

A new method for biological synthesis of agriculturally relevant nanohydroxyapatite with elucidated effects on soil bacteria.

The study describes a novel and environment friendly route of biosynthesis of nanohydroxyapatite (nHAP). Bacillus licheniformis mediated synthesis of nHAP has been carried out with different phosphate concentrations (2%, 5%, 10% and 20% w/v) of potassium dihydrogen orthophosphate monobasic (K2HPO4). The synthesis is supported by a two-step mechanism - (i) solubilization of P by organic acids extracellularly secreted by the bacterial strain and (ii) gelation of P and Ca. The nHAP particles were characterized using electron microscopy and XRD analysis. Powdered crystalline particles with a size range of 30 ± 5 nm were obtained with shape and size dependent on phosphate concentrations. The particles showed no adverse effect on plant growth-promoting bacteria. Evaluation of nHAP prepared by this route with 2% P source provides scope for a wide range of applications, especially as a nano-fertilizer.

Assessing omniphobicity by immersion.

HYPOTHESIS: Coating-free approaches to achieve liquid repellent, or omniphobic, surfaces could exploit inexpensive intrinsically wetting materials, such as polyethylene terephthalate and nylon, for applications such as liquid-vapor extraction and drag reduction. However, it is not clear whether the existing criteria for assessing coating-based omniphobicity, based on contact angles, would be reliable for coating-free approaches, especially considering localized defects/damages during manufacturing and usage. EXPERIMENTS: We assessed the omniphobicity of silica surfaces adorned with arrays of doubly reentrant pillars, cavities, and hybrid designs with sessile drops and on immersion in water and hexadecane through contact angle goniometry and confocal microscopy. FINDINGS: We demonstrate that the assessment of omniphobicity of surfaces derived from intrinsically wetting materials can be misleading, if solely based on the measurement of contact angles. Specifically, localized defects in microtextures consisting of pillars may lead to the spontaneous loss of omniphobicity and detecting them through contact angles can be difficult. We also demonstrate that the immersion of those surfaces into probe liquids may serve as a simple and quick 'litmus' test for omniphobicity. Thus, immersion as the additional criterion for omniphobicity might prove itself useful in the context of large-scale manufacturing.

Vanillin mediated green synthesis and application of gold nanoparticles for reversal of antimicrobial resistance in Pseudomonas aeruginosa clinical isolates.

Antimicrobial resistance (AMR) is a serious concern in pathogenic bacteria. As a new approach to addressing AMR, we report here the green synthesis of vanillin capped gold nanoparticles (VAuNPs) using the popular flavouring molecule vanillin (C8H8O3) as a reducing and capping agent. Physicochemical characterization revealed that the synthesised VAuNPs were stable and crystalline in nature. VAuNPs were non-bactericidal even at high concentration (>2000 µg/ml). The antibiotic potentiation activity was studied in combination with seven widely used antibiotics against extremely drug resistant (XDR) Pseudomonas aeruginosa. Major reductions in minimum inhibitory concentrations (MIC, 10-14-folds) of the antibiotics meropenem (10 fold) and trimethoprim (14 fold) were observed in the presence of VAuNPs (50 µg/ml). Furthermore, it was found that VAuNPs in combination with meropenem or trimethoprim provided 1.5-3-fold better potentiation effects than that of vanillin alone. Use of an ethidium bromide agar cart wheel assay indicated that VAuNPs can block the activity of efflux pumps. High reduction in the MIC of antibiotics was therefore attributed to the efflux pump repression activity of VAuNPs. Further, RT-qPCR of clinically relevant MexAB-OprM efflux pump components showed down-regulation in mexB and OprM transcripts in VAuNPs treated P. aeruginosa clinical isolates. Our results reveal that VAuNPs impart susceptibility to the last line antibiotics meropenem, trimethoprim and few widely used antibiotics in XDR P. aeruginosa clinical isolates that display resistance to these antibiotics. Therefore, this study indicate the ability of VAuNPs and vanillin to be used as antibiotic adjuvants for inhibiting bacterial efflux pumps to potentiate antibiotics for addressing AMR problem affecting human health and environment.