Quantum Dots-Based Nano-Coatings for Inhibition of Microbial Biofilms: A Mini Review

Infection of implants by microbial biofilm is chiefly caused by Staphylococci, Pseudomonas and Candida species. The growth of microbes by forming biofilms offers them protection from antibiotics, drugs and host defense mechanisms. The eradication of biofilms from implants and medical devices is difficult because of the protection by the biofilm forming pathogenic microbes. Hence, researches are focused on development of antibiofilm materials, which are basically constituted of antimicrobial substances or antimicrobial coatings. Nanomaterial-based coatings offer a promising solution in this regard. Quantum dots (QDs) are the group of semiconductor nanoparticles with high photoluminescent properties compared to conventional organic fluorophores. Thus, drug-conjugated QDs can be a promising alternative for biofilm treatment, and these can serve as excellent alternatives for the mitigation of recalcitrant biomaterial-associated infections caused by resistant strains. Furthermore, their use as antibiofilm coating would avoid the dispersion of antimicrobial agents in the surrounding cells and tissues, thereby minimizing the risks of developing microbial resistivity

Idiopathic Hypertrophy of the Masseter Muscle

A short summary of the literature on masseter hypertrophy has been given along with the findings from our own series of eight cases. The salient features of our findings are that the condition is perhaps related to some type of work hypertrophy, in our cases bitel-nut chewing; that only for marked cosmetic deformity is surgical interference indicated; we prefer the extraoral appre ach with excision of the external portion of the muscle, which may be combined with excision of the hyperostotic bone where necessary; ordinary histological examination does not reveal any changes in the muscle histology but special technique like silver staining could help. Radiology of the mandible shows definite changes in the form of abnormal bone growth at the mandibular angle and reduction in the angulation of the angle from an average of 120° to an average 90°

Universal Charge Quenching and Stability of Proteins in 1‑Methyl-3-alkyl (Hexyl/Octyl) Imidazolium Chloride Ionic Liquid Solutions

This study reports pH dependent stability of protein dispersions of five common proteins, bovine serum albumin (BSA), human serum albumin (HSA), immunoglobulin (IgG), β-lactoglobulin (β-Lg), and gelatin-B (Gel-B), all having isoelectric pH, p<i>I</i> ≈ 5, in room temperature ionic liquid solutions of 1-methyl-3-alkyl (hexyl/octyl) imidazolium chloride (concentration 0–0.2% <i>w</i>/<i>v</i>). Molecular hydrophobicity index, (H-index = hydrophobicity/hydrophilicity) of these molecules spanned the range 0.43–0.87. Electrophoretic characteristics, surface tension data and hydrodynamic size information revealed that IL solutions provide dispersion stability owing to specific protein-IL binding which did not alter their pI values though their surface charge was considerably screened. Change in maximum (ζ_max) and minimum (ζ_min) zeta potential values observed at pH ∼3 (maximum protonated state) and pH ∼8 (maximum deprotonated state) could be described universally as function of IL concentration, <i>c</i> as Δζ_<i>x</i> = [1 – exp­(−<i>ac</i>)] where Δζ_<i>x</i> is either |(ζ_max – ζ_w)|/ζ_w or |(ζ_min – ζ_w)|/ζ_w, and ζ_w is the corresponding value in water. Tensiometry data showed two major stages of protein-IL interactions: (i) for <i>c</i> < cmc of IL, the IL molecules selectively bind with imidazolium cation through electrostatic forces forming protein-IL _complex and (ii) for c> cmc free IL-aggregates begin to form. Similarly, we can define Δγ_<i>x</i> as either |(γ_max – γ_w)|/γ_w at pH 3 or |(γ_min – γ_w)|/γ_w at pH 8. Both Δζ_<i>x</i> and Δγ_<i>x</i> showed linear dependence with <i>c</i>, Δγ_min, max (or Δζ_min, max) = (1 – <i>K</i>_γ (or <i>K</i>_ζ) H-index), where the slopes <i>K</i>_ζ and <i>K</i>_γ defined intermolecular interactions. Hydrodynamic radii data revealed protein stabilization, circular dichroism spectra implied retention of secondary structures, and Raman spectra confirmed a marginal increase in water structure. Results concluded that selective binding of IL molecules to protein surface in the form of bilayer screen protein surface charge, thereby, contributing to its dispersion stability

Biocompatible laponite ionogels based non-enzymatic oxalic acid sensor

An enzyme-free oxalic acid (OA) electrochemical sensor was assembled on indium tin oxide (ITO) plate on which a film of laponite ionogel was coated that resulted in an L/IL/ITO electrode. This ionogel electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and UV–Vis spectroscopy techniques. Electrochemical oxidation of OA on the electrode surface was investigated by cyclic voltammetry. Further this electrode exhibited high electrochemical activity that yielded well-defined peaks of OA oxidation, and a notably suppressed over-potential compared to the laponite–ITO (L/ITO) electrode. Under optimized conditions, a good linear response (anodic current) was observed for the OA concentration in the 1–20 mM range with a detection limit of 3 μM. Furthermore, this electrochemical strip sensor presented good characteristics in terms of stability, and reproducibility offering promise of applicability of this green sensor platform. Keywords: Ionogels, Enzyme-free, Oxalic acid, Biosensor, Cyclic voltammetr

DNA–Gelatin Complex Coacervation, UCST and First-Order Phase Transition of Coacervate to Anisotropic ion gel in 1‑Methyl-3-octylimidazolium Chloride Ionic Liquid Solutions

Study of kinetics of complex coacervation occurring in aqueous 1-octyl-3-methylimidazolium chloride ionic liquid solution of low charge density polypeptide (gelatin A) and 200 base pair DNA, and thermally activated coacervate into anisotropic gel transition, is reported here. Associative interaction between DNA and gelatin A (GA) having charge ratio (DNA:GA = 16:1) and persistence length ratio (5:1) was studied at fixed DNA (0.005% (w/v)) and varying GA concentration (<i>C</i>_GA = 0–0.25% (w/v)). The interaction profile was found to be strongly hierarchical and revealed three distinct binding regions: (i) Region I showed DNA-condensation (primary binding) for <i>C</i>_GA < 0.10% (w/v), the DNA ζ potential decrease from −80 to −5 mV (95%) (partial charge neutralization), and a size decrease by ≈60%. (ii) Region II (0.10 < <i>C</i>_GA < 0.15% (w/v)) indicated secondary binding, a 4-fold turbidity increase, a ζ potential decrease from −5 to 0 mV (complete charge neutralization), which resulted in the appearance of soluble complexes and initiation of coacervation. (iii) Region III (0.15 < <i>C</i>_GA < 0.25% (w/v)) revealed growth of insoluble complexes followed by precipitation. The hydration of coacervate was found to be protein concentration specific in Raman studies. The binding profile of DNA-GA complex with IL concentration revealed optimum IL concentration (=0.05% (w/v)) was required to maximize the interactions. Small angle neutron scattering (SANS) data of coacervates gave static structure factor profiles, <i>I</i>(<i>q</i>) versus wave vector <i>q</i>, that were remarkably similar and invariant of protein concentration. This data could be split into two distinct regions: (i) for 0.0173 < <i>q</i> < 0.0353 Å^–1, <i>I</i>(<i>q</i>) ∼ <i>q</i>^–α with α = 1.35–1.67, and (ii) for 0.0353 < <i>q</i> < 0.35 Å^–1, <i>I</i>(<i>q</i>) = <i>I</i>(0)/(1 + <i>q</i>²ξ²). The correlation length found was ξ = 2 ± 0.1 nm independent of protein concentration. The viscoelastic length (≈8 nm) was found to have value close to the persistence length of the protein (≈10 nm). Rheology data indicated that the coacervate phase resided close to the gelation state of the protein. Thus, on a heating–cooling cycle (heating to 50 °C followed by cooling to 20 °C), the heterogeneous coacervate exhibited an irreversible first-order phase transition to an anisotropic ion gel. This established a coacervate–ion gel phase diagram having a well-defined UCST

Hierarchical Surface Charge Dependent Phase States of Gelatin–Bovine Serum Albumin Dispersions Close to Their Common pI

We report interaction between bovine serum albumin ([BSA] = 1% (w/v)) and gelatin B ([GB] = 0.25–3.5% (w/v)) occurring close to their common isoelectric pH (pI). This interaction generated distinguishable multiple soft matter phases like opaque coacervates (phase I) and transparent gels (phase II), where the former are composed of partially charge neutralized intermolecular complexes (zeta potential, ζ ≤ 0) and the latter of overcharged complexes (ζ ≥ 0) that organized into a network pervading the entire sample volume. These phase states were completely governed by the protein mixing ratio <i>r</i> = [GB]:[BSA]. Coacervates, when heated above 32 °C, produced thermoirreversible turbid gels (phase III), stable in the region 32 ≥ <i>T</i> ≤ 50 °C. When the transparent gels were heated to <i>T</i> ≥ 34 °C, these turned into turbid solutions that did form a turbid fragile gel (phase IV) upon cooling. Mechanical and thermal behaviors of aforesaid coacervates (phase I) and gels (phase II) were examined; coacervates had lower storage modulus and melting temperature compared to gels. Cole–Cole plots attributed considerable heterogeneity to coacervate phase, but gels were relatively homogeneous. Raman spectroscopy data suggested differential microenvironment for these phases. Coacervates were mostly hydrated by partially structured water with degree of hydration dependent on gelatin concentration whereas for gels hydration was invariant of [GB]. Small-angle neutron scattering (SANS) data gave static structure factor profiles, <i>I</i>(<i>q</i>), versus wavevector <i>q</i>, that were remarkably different. For transparent gels, data could be split into two distinct regions: (i) 0.01 < <i>q</i> < 0.1 Å^–1, <i>I</i>(<i>q</i>) = <i>I</i>_OZ(0)/(1 + <i>q</i>²ζ_gel²)² (Debye–Bueche function) with ζ_gel = 9–13 nm, and (ii) 0.1 < <i>q</i> < 0.35 Å^–1, <i>I</i>(<i>q</i>) = <i>I</i>_OZ(0)/(1 + <i>q</i>²ξ_gel²) (Ornstein–Zernike function) with ξ_gel = 3.1 ± 0.6 nm. Similarly, for coacervate, the aforesaid two <i>q</i>-regions were described by (i) <i>I</i>(<i>q</i>) = <i>I</i>_PL(0)<i>q</i>^–α with α = 1.7 ± 0.1 and (ii) <i>I</i>(<i>q</i>) = <i>I</i>_OZ(0)/(1 + <i>q</i>²ξ_coac²) with ξ_coac = 1.6 ± 0.2 nm, a value close to the persistence length of gelatin chain (<i>l</i>_p ≈ 2 nm). Phase transition from one equilibrium state to another, i.e., phase I to II, was hierarchical in the charge state of the protein–protein complex. Within the same charge state, transition from phase I to III and from phase II to IV was thermally activated. The aforesaid mechanisms are captured in a unique ζ–<i>T</i> phase diagram

Single electron transfer-driven multi-dimensional signal read-out function of TCNQ as an ``off-the-shelf'' detector for cyanide

Herein we report the first applications of TCNQ as a rapid and highly sensitive off-the-shelf cyanide detector. As a proof-of-concept, we have applied a kinetically selective single-electron transfer (SET) from cyanide to deep-lying LUMO orbitals of TCNQ to generate a persistently stable radical anion (TCNQ(center dot-)), under ambient condition. In contrast to the known cyanide sensors that operate with limited signal outputs, TCNQ(center dot-) offers a unique multiple signaling platform. The signal readability is facilitated through multichannel absorption in the UV-vis-NIR region and scattering-based spectroscopic methods like Raman spectroscopy and hyper Rayleigh scattering techniques. Particularly notable is the application of the intense 840 nm NIR absorption band to detect cyanide. This can be useful for avoiding background interference in the UV-vis region predominant in biological samples. We also demonstrate the fabrication of a practical electronic device with TCNQ as a detector. The device generates multiorder enhancement in current with cyanide because of the formation of the conductive TCNQ(center dot-)

Bioaccumulation of CdSe Quantum Dots Show Biochemical and Oxidative Damage in Wistar Rats

Cadmium selenium quantum dots (CdSe QDs) with modified surfaces exhibit superior dispersion stability and high fluorescence yield, making them desirable biological probes. The knowledge of cellular and biochemical toxicity has been lacking, and there is little information on the correlation between in vitro and in vivo data. The current study was carried out to assess the toxicity of CdSe QDs after intravenous injection in Wistar male rats (230 g). The rats were given a single dose of QDs of 10, 20, 40, and 80 mg/kg and were kept for 30 days. Following that, various biochemical assays, hematological parameters, and bioaccumulation studies were carried out. Functional as well as clinically significant changes were observed. There was a significant increase in WBC while the RBC decreased. This suggested that CdSe quantum dots had inflammatory effects on the treated rats. The various biochemical assays clearly showed that high dose induced hepatic injury. At a dose of 80 mg/kg, bioaccumulation studies revealed that the spleen (120 g/g), liver (78 g/g), and lungs (38 g/g) accumulated the most. In treated Wistar rats, the bioretention profile of QDs was in the following order: the spleen, liver, kidney, lungs, heart, brain, and testis. The accumulation of these QDs induced the generation of intracellular reactive oxygen species, resulting in an alteration in antioxidant activity. It is concluded that these QDs caused oxidative stress, which harmed cellular functions and, under certain conditions, caused partial brain, kidney, spleen, and liver dysfunction. This is one of the most comprehensive in vivo studies on the nanotoxicity of CdSe quantum dots

Divergent Responses of Hydrophilic CdSe and CdSe@CdS Core–Shell Nanocrystals in Apoptosis and In Vitro Cancer Cell Imaging: A Comparative Analysis

With their distinctive core–shell design, core–shell nanocrystals have drawn interest in catalysis, medicinal research, and nanotechnology. These nanocrystals have a variety of characteristics and possible uses. The application of core–shell nanocrystals offers significant potential in increasing diagnostic and therapeutic approaches for cancer research in apoptosis and in vitro cancer cell imaging. In the present study, we investigated the fluorescence behavior of hydrophilic CdSe (core-only) and CdSe@CdS (core–shell) nanocrystals (NCs) and their potential in cancer cell imaging. The addition of a CdS coating to CdSe NCs increased the fluorescence intensity tenfold. The successful fabrication of core–shell CdSe@CdS nanocrystals was proven by a larger particle size (evaluated via DLS and TEM) and their XRD pattern and surface morphology compared to CdSe (core-only) NCs. When these NCs were used for bioimaging in MCF-7 and HEK-293 cell lines, they demonstrated excellent cellular uptake due to higher fluorescence intensity within cancerous cells than normal cells. Comparative cytotoxicity studies revealed that CdSe NCs were more toxic to all three cell lines (HEK-293, MCF-7, and HeLa) than CdSe@CdS core–shell structures. Furthermore, a decrease in mitochondrial membrane potential and intracellular ROS production supported NCs inducing oxidative stress, which led to apoptosis via the mitochondria-mediated pathway. Increased cytochrome c levels, regulation of pro-apoptotic gene expression (e.g., p53, Bax), and down-regulation of Bcl-2 all suggested cellular apoptosis occurred via the intrinsic pathway. Significantly, at an equivalent dose of core–shell NCs, core-only NCs induced more oxidative stress, resulting in increased apoptosis. These findings shed light on the role of a CdS surface coating in reducing free radical release, decreasing cytotoxicity, and improving fluorescence, advancing the field of cell imaging