Water Condensation and Protein Adsorption on Hybrid Superhydrophobic-Hydrophilic Surfaces

This thesis describes the study of protein adsorption and water condensation on hybrid superhydrophobic-hydrophilic surfaces for various technological applications such as diagnostics, artificial organs and medical devices, water collection, and heat transfer. In the chapter 1, a general introduction to wetting theories, superhydrophobic surface, and hybrid surfaces is given. In chapter 2, design and fabrication of a hybrid superhydrophobic surface for studying dropwise condensation and heat transfer is discussed. Effect of surface chemistry and wettability on protein adsorption is discussed in the chapter 3. Finally, in chapter 4, the protein adsorption study on hybrid superhydrophobic surfaces made by 3D-printing and subsequent coating of the surface with modified silica nanoparticles to understand the effect of surface roughness and wettability on protein adsorption is described. Condensation of water vapor is an essential process in power generation, water collection, and thermal management. Because of the high surface energy of the metal surfaces, filmwise condensation of water vapor occurs, forming a static, thermally insulating film. Numerous efforts have been made to create surfaces that promote dropwise condensation; however these efforts result in thermally insulating layers or degrade over time. Nature provides an alternative approach. The Namib beetle (Stenocara gracilipes) has a carapace that collects water by promoting dropwise condensation on raised hydrophilic regions which then roll off and slide along the hydrophobic surface. We designed and fabricated a hybrid superhydrophobic-hydrophilic surface to mimic, and improve upon, this behavior. An array of hydrophilic needles, thermally connected to a heat sink, was forced through a robust superhydrophobic polymer film. Condensation occurs preferentially on the needle surface due to differences in wettability and temperature. As the droplet grows, the liquid drop on the needle remains in the Cassie state and does not wet the underlying superhydrophobic surface after 5 days of testing. The water collection rate on this surface was studied using different surface tilt angles, needle array pitch values and needle heights. Water condensation rates on the hybrid surface were shown to be 4 times greater than for a planar copper surface and twice as large for hydrophobic silicon or superhydrophobic surfaces without hydrophilic features. A convection-conduction heat transfer model was developed; predicted water condensation rates were in good agreement with experimental observations. This type of hybrid superhydrophobic-hydrophilic surface with a larger array of needles could be used for heat transfer and water collection applications. In chapter 3, we study the effect of surface chemistry and wettability on the adsorption of proteins with the goal of designing protein repellent, biocompatible, surfaces for medical devices, diagnostics, pharmaceutical and food processing applications. To this purpose oxidized silicon wafers were modified to render them either hydrophilic or hydrophobic. Hydrophilic surfaces with different surface chemistry were prepared by attaching: a) polyethylene glycol silane (PEG) or b) a zwitterionic siloxane (sulfobetaine siloxane; SBS) to the oxide surface. Hydrophobic surfaces were prepared by coating the silicon oxide surface with: a) methyl terminated polydimethyl siloxane (PDMS), or b) a chemical vapor deposition of dimethyl dichlorosilane (DMDCS). Prepared surfaces were characterized by contact angle goniometry and X-ray photoelectron spectroscopy (XPS). Surfaces were exposed to protein solutions of bovine serum albumin (BSA), fibrinogen, and lysozyme. The protein adsorption on the prepared surfaces were studied as a function of time using confocal fluorescence microscopy (CFM), XPS and contact angle (CA) measurement techniques. Maximum protein adsorption was observed on clean, unmodified hydrophilic silica surfaces (CA ~ 4°). Almost no protein was observed on PEG- and SBS-coated hydrophilic surfaces as indicated by CFM and XPS. Intermediate amounts of protein adsorption were observed on hydrophobic surfaces. Protein absorption was shown to change the wettability of the surface as measured by changes in CA. PEG- and SBS-modified surfaces showed almost no change in CA, which indicated little or no protein adsorption. Coating of a hydrophilic silicon dioxide surface with PEG or SBS was shown to be an effective approach to designing protein repellent surfaces. This study examines the idea how the surface chemistry and wettability affect the protein adsorption on a flat surface (without any roughness). In the next chapter (Chapter 4), these findings and techniques are applied to study protein adsorption in a complex rough surface to study the effect of surface roughness and wettability on protein adsorption. Hopefully, that will help us to design an effective protein repellent surface for application in diagnostics and other applications where less non-specific protein adsorption is desired. Superhydrophobic surfaces that show high water contact angles (˃150°)and low slip angles (˂10°)have been explored for various applications due to their excellent self-cleaning and low adhesion properties.Proteins and cells can adhere to hydrophobic surfaces, however, due to interactions between the hydrophobic portion of the protein and the hydrophobic surface, resulting in surface fouling. As a result of this change in surface wetting, the hydrophobic properties of the surfaces are lost. In the previous chapter, the hydrophilic coating with polyethylene glycol or zwitterionic molecules on the flat surfaces has been shown to be especially effective at preventing protein adsorption. In this chapter I have prepared superhydrophobic surfaces using hydrophilic nanoparticles to make protein-resistant surfaces. The effect of surface chemistry and roughness on the wetting behavior of superhydrophobic silica/silicone hybrid surfaces was also studied. In addition, the absorption of proteins on these surfaces was investigated with BSA as model protein with the goal of designing biocompatible super repellent surfaces for biomedical applications. Superhydrophobic surfaces made with TS530 were shown to adsorb minimum amount of protein

Goggle Augmented Imaging and Navigation System for Fluorescence-Guided Surgery

Surgery remains the only curative option for most solid tumors. The standard-of-care usually involves tumor resection and sentinel lymph node biopsy for cancer staging. Surgeons rely on their vision and touch to distinguish healthy from cancer tissue during surgery, often leading to incomplete tumor resection that necessitates repeat surgery. Sentinel lymph node biopsy by conventional radioactive tracking exposes patients and caregivers to ionizing radiation, while blue dye tracking stains the tissue highlighting only superficial lymph nodes. Improper identification of sentinel lymph nodes may misdiagnose the stage of the cancer. Therefore there is a clinical need for accurate intraoperative tumor and sentinel lymph node visualization. Conventional imaging modalities such as x-ray computed tomography, positron emission tomography, magnetic resonance imaging, and ultrasound are excellent for preoperative cancer diagnosis and surgical planning. However, they are not suitable for intraoperative use, due to bulky complicated hardware, high cost, non-real-time imaging, severe restrictions to the surgical workflow and lack of sufficient resolution for tumor boundary assessment. This has propelled interest in fluorescence-guided surgery, due to availability of simple hardware that can achieve real-time, high resolution and sensitive imaging. Near-infrared fluorescence imaging is of particular interest due to low background absorbance by photoactive biomolecules, enabling thick tissue assessment. As a result several near-infrared fluorescence-guided surgery systems have been developed. However, they are limited by bulky hardware, disruptive information display and non-matched field of view to the user. To address these limitations we have developed a compact, light-weight and wearable goggle augmented imaging and navigation system (GAINS). It detects the near-infrared fluorescence from a tumor accumulated contrast agent, along with the normal color view and displays accurately aligned, color-fluorescence images via a head-mounted display worn by the surgeon, in real-time. GAINS is a platform technology and capable of very sensitive fluorescence detection. Image display options include both video see-through and optical see-through head-mounted displays for high-contrast image guidance as well as direct visual access to the surgical bed. Image capture options from large field of view camera as well high magnification handheld microscope, ensures macroscopic as well as microscopic assessment of the tumor bed. Aided by tumor targeted near-infrared contrast agents, GAINS guided complete tumor resection in subcutaneous, metastatic and spontaneous mouse models of cancer with high sensitivity and specificity, in real-time. Using a clinically-approved near-infrared contrast agent, GAINS provided real-time image guidance for accurate visualization of lymph nodes in a porcine model and sentinel lymph nodes in human breast cancer and melanoma patients with high sensitivity. This work has addressed issues that have limited clinical adoption of fluorescence-guided surgery and paved the way for research into developing this approach towards standard-of-care practice that can potentially improve surgical outcomes in cancer

Optimisation using central composite design (CCD) and the desirability function for sorption of methylene blue from aqueous solution onto Lemna major

AbstractWater pollution due to contamination of dye containing effluents is a great threat to water body. A study on the biosorption of methylene blue (MB) onto low-cost Lemna major biomass was conducted and the process parameters were optimized by response surface methodology (RSM). A two-level, four-factor central composite design (CCD) has been employed to determine the effect of various process parameters namely initial concentration (600–1000 mg L−1), bioadsorbent dose (0.20–1.50 g/100 mL), pH (5–12) and stirring rate (250–800 rpm) on MB uptake from aqueous solution. By using this design a total of 30 biosorption experimental data were fitted. The regression analysis showed good fit of the experimental data to the second-order polynomial model with coefficient of determination (R2) value of 0.9978 and model F-value of 953.48. The optimum conditions of initial concentration (1000 mg L−1), adsorbent dose (0.2 g), pH (5) and stirring rate (251.51 rpm) were recorded from desirability function. The adsorption isotherm data were best described by both Freundlich and Langmuir models with a maximum adsorption capacity of 488 mg MB g−1 L. major biomass at 30 °C which is higher than that available with adsorbents used by past researchers. Finally the pseudo second order kinetic model described the MB biosorption process with a good fitting (R2 = 0.999). The adsorbent was characterised by scanning electron micrograph (SEM) and Fourier transform infrared spectroscopy (FTIR)

The beneficial role of N-acetylcysteine as an adjunctive drug in treatment of COVID-19 patients in a tertiary care hospital in India: an observational study

Background: N-acetyl cysteine, a mucolytic agent, demonstrates free radical scavenging and anti-inflammatory properties, and prevents endothelial dysfunction by inhibition of NF-KB and formation of no adducts. This has a potential role to tackle cytokine storms, endothelial dysfunction and prothrombotic state observed in COVID-19 manifestations like ARDS and Multi organ dysfunction.Methods: Institution based descriptive cross sectional study, 164 patients from laboratory confirmed RT PCR positive COVID-19 patients, in the study period from 27th May 2020 to 10th August 2020, were assessed, in medical college Kolkata, a dedicated COVID-19 care facility.Results: It was observed that moderate-severe patients who received N-acetyl cysteine along with standard therapy had average hospital stay duration of 12 days, higher rate of discharge, average duration of oxygen therapy of 8 days, less number of deaths and reduced transfer to critical care facilities.Conclusions: N-acetyl cysteine can be considered as an adjunctive therapy with standard protocol driven care, due to its beneficial anti-inflammatory and free radical scavenging properties

Thermodynamic and kinetic characteristics of an a-amylase from Bacillus licheniformis SKB4

An amylolytic bacterial strain, Bacillus licheniformis SKB4 produced maximum amylase at pH 6.5 at 42 °C, and at late stationary phase (24 h) of growth. Starch and peptone were found the best supporting carbon and nitrogen source with C:N ratio of 1:2 for amylase production. The purified enzyme was non-responsive to most of the metal ions except K+ and Mg++ (1.0 mM). The enzyme was stable and active at pH 6.5. The enzyme showed optimum temperature at 90 °C with 10 min of half life (t½) at 100 °C. The Q10 of the enzyme was 1.0. The thermodynamic principles like activation energy, free energy for substrate binding and transition state of the enzyme were found 31.53, 5.53 and -17.4 KJ/Mol of starch, respectively. The kinetic constant like Vmax, Km, K catand catalytic efficiency (Kcat/Km)for starch were found to be 1.04 μmol mg-1 min-1, 6.2 mg ml-1,2 × 103 S-1 and 3.22 × 102 ml mg-1 S-1,respectively. All these findings suggested that this amylase has unique characteristics for starch hydrolysis in respect to thermostability and kinetic properties

Cutaneous Leishmaniasis in an Immigrant Saudi Worker: A Case Report

Cutaneous leishmaniasis (CL), an uncommon disorder in South-East Asia, including Bangladesh, often presents as granulomatous plaque on the exposed areas, with a high index of suspicion required for diagnosis. Here we report the first imported case of CL caused by Leishmania tropica in a migrant Bangladeshi worker in the Kingdom of Saudi Arabia (KSA). The case, initially suspected as a case of cutaneous tuberculosis, arrived at specimens reception unit (SRU) of diagnostic labs of icddr,b being referred by the physician for ALS testing for tuberculosis. At his arrival in the SRU, one of the health personnel of the unit who used to work in KSA suspected him as a case of CL. The diagnosis was confirmed by smear microscopy which revealed plenty of amastigotes within macrophages. PCR was performed to confirm the species. He was treated with sodium stibogluconate at Shahid Suhrawardy Medical College Hospital, Dhaka

The role of life events in obsessive-compulsive disorders

Background: A small number of studies are available to assess the role of stressful life events (SLEs) in obsessive-compulsive disorder (OCD). The previous studies have reported contradictory results and they have methodological limitations. Aims and Objectives: The objectives of our study are (i) to find out the frequency of life events in patients with OCD in comparison to their matched healthy controls and (ii) to find out the impact of life events on the severity of the disorder. Materials and Methods: Sixty patients fulfilling Diagnostic and Statistical Manual of Mental Disorder, 5th edition (DSM-V) criteria of OCD were rated with Yale-Brown Obsessive Compulsive Scale (Y-BOCS), Hamilton Rating Scale for Anxiety (HAM-A), Hamilton Rating Scale for Depression (HAM-D), and Presumptive Stressful Life Events Scale (PSLES). A group of 60 normal controls were also rated on PSLES. Finally, both groups were compared in terms of life events. Results: The frequency of life events, past 1 year (t=5.307, P=0.006) and lifetime (t=11.527, P<0.001), were significantly higher in the patient group in comparison to controls. PSLES scores showed a significant correlation with Y-BOCS total scores, Y-BOCS obsession scores, and HAM-A scores. There was a positive correlation between past 1 year PSLES score and HAM-D scores. Step-wise linear regression analysis showed PSLES scores significantly positively predicted Y-BOCS total score, Y-BOCS obsession score, and Y-BOCS compulsion score. Conclusion: Life events were significantly more frequent in OCD patients both past 1 year and lifetime, as compared to healthy controls. The severity of obsessive compulsive symptoms was found to be directly proportional to the number of SLEs experienced in the past 1 year and lifetime

Screening of antimicrobial peptides from hemolymph extract of tasar silkworm Antheraea mylitta against urinary tract and wound infecting multidrug-resistant bacteria

Antimicrobial peptides (AMPs) are an evolutionarily conserved component of the innate immune response and they were found among all classes of life forms. In the present study AMPs were extracted from the hemolymph of Antheraea mylitta and fractionated by High Performance Liquid Chromatography (HPLC). Antimicrobial activity was tested against three clinically isolated multidrug-resistant (MDR) bacteria, such as urinary tract infecting Escherichia coli, wound infecting Pseudomonas aeruginosa and Bacillus pumilus. Fraction I (comprised of three different peptides of varying mass) did not inhibit the growth of any of these clinical isolates, whereas, fraction III inhibited the growth of B. pumilus without affecting the growth of gram-negative isolates. Fraction II exhibited bactericidal effects against P. aeruginosa and E. coli, whereas, B. pumilus was not susceptible. Scanning electron microscopic study revealed that serious structural alterations of cell morphology and disruption of the outer membrane, that facilitates the release of cytoplasmic content through holes and channels in E. coli, treated with this isolated peptide. Our results indicate that the peptide from the isolated fraction could be used as potent alternative antimicrobial compounds for the treatment of MDR E. coli andP. aeruginosa infections

Ethnic Preparation of Haria, a Rice-Based Fermented Beverage, in the Province of Lateritic West Bengal, India

Haria is a rice-based fermented beverage that is popular among tribal and low income people in lateritic West Bengal and East-Central India. The principal ingredient of this beverage is low grade boiled rice (Oryza sativa L.), which is mixed with a traditional starter, called bakhar, and fermented within a heat-sterilized earthen pot for 3-4 days. The main aim of this study was to investigate the ethnobotanical importance and traditional process of haria preparation. The method adopted for this study was based on interactive questionnaires and laboratory experiments. It was found that the pH decreased during the course of fermentation with increased titratable acidity of 1.42%. The alcohol content was 2-3% (v/v) in the consumable beverages. This documentation will be useful for further exploitation of haria as a health drink