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The use of TiO2 nanoparticles (NPs) in a wide range of products (specially biomedical applications) in day-to-day life and the notable fact that it is photoactive and generates reactive oxygen species (ROS) create curiousness among researchers to study their effects on different biological systems. Heme-enzymes are known to operate redox reactions in living system in tandem with ROS. Horseradish peroxidase (HRP) being a model heme-enzyme from the peroxidase family was systematically studied for enzymatic changes after interaction with TiO2 NPs under physiologically relevant pH and irradiation conditions. This study gives us an extensive idea of the changes in enzyme kinetics, intrinsic fluorescence, interaction efficiency, and stability of the protein–nanoparticle complex formed. The effect of ROS generated by TiO2 NPs under different irradiation conditions was substantially considered as one of the major factors that influenced the enzyme kinetics apart from protein adsorption on the surface of nanoparticles. The impact of excessive use of TiO2 NPs on the activity of HRP can be discerned from the current study.

The impact of bio-remediation agent nZVI on environment is still inadequately understood, especially on aquatic food web. The study presented here has therefore considered both chemical (CS) and biological (BS) synthetic origins of nZVI and their effects on both algae and daphnia. The study is unique in its attempt to explore the possibility of trophic transfer from algae to its immediate higher niche (daphnia as the model). An equal weightage of the effects of both CS and BS nZVI on algae and daphnia has been explored here; hence it allows us to compare the capping of nZVI on toxicity. To examine the causes of observed lethality- ROS generation, effects on the activity of oxidative enzymes, membrane damage and biouptake of nZVI was analysed. The overall outcome of CS and BS nZVI on lethality was significantly different in algae and daphnia, where daphnia demonstrated relatively higher sensitivity against CS nZVI. Algae demonstrated considerable differences in CS and BS nZVI toxicity only at higher concentration. This study did not show a probable biomagnification and trophic transfer from algae to daphnia under the experimental conditions even at the highest exposure concentration. The study instigates the importance of trophic transfer to understand the possible biomagnification of nZVI among organisms of different trophic levels and eventually the consequences on environment.

TiO2 NPs is one of the major components of paints and sunscreens and also acts as a catalyst for waste water treatment. The study demonstrates the toxic effects of TiO2 NPs on an anaerobic bacterium, Macrococcus caseolyticus, isolated from the activated sludge of a waste water treatment facility. The cytotoxicity assessment under UVA, visible light, and dark conditions revealed a dose- and exposure-dependent reduction in viability. The examination of cytotoxicity was performed with membrane permeability assessment through LDH (Lactate dehydrogenase) detection. The formation of exopolymeric substances (EPS) was observed to be dose-dependent, and maximum EPS release was noted under UVA condition. The scanning electron microscopy described the aggregation tendency of biofilm to be more pronounced under UVA condition when treated with TiO2 NPs as compared to the control biofilm. Uptake of TiO2 NPs by the biofilm indicated possible remediation of the NPs in waste water by these organisms.

The biocatalytic growth of metal nanoparticles for the detection of environmentally relevant chemical molecules is a recently exploited strategy. The present work provides a new synthesis methodology for gold nanoparticles (GNPs), which could be enzymatically modulated by horseradish peroxidase (HRP). Gold seeds (∼10 nm) were prepared initially by the reduction of HAuCl4 using a minimal concentration of NaBH4, and the further biocatalyzed GNP formation was assisted by HRP, its substrate, and hydrogen peroxide (H2O2 helps in complete formation of GNPs). Upon HRP inhibition, the enzymatic formation of GNPs was observed to decrease with increasing concentrations of phenylhydrazine (HRP inhibitor) using a simple UV-visible spectrophotometer. The current method provides an in situ enzymatic assay based on the biocatalyzed rate of GNP formation for the rapid, reproducible, and cost-effective detection of phenylhydrazine with a detection limit of 4.02 μM (range: 25–200 μM). The proposed technique was also successfully tested in real samples like drinking, tap, and garden water, emphasizing its usefulness for the direct on-site monitoring of phenylhydrazine, and the concept can be extended for the detection of other inhibitors of peroxidase also.

Gold nanoparticles (GNPs) are widely used for medical purposes, both in diagnostics as well as drug delivery, and hence are prone to release and distribution in the environment. Thus, we have explored the effects of GNPs with two distinct surface capping (citrate and PVP), and three different sizes (16, 27, and 37 nm) at 0.01-, 0.1-, and 1-mg L−1 concentrations on a predominant freshwater alga Scenedesmus obliquus in the sterile freshwater matrix. We have also investigated how an abundant metal ion from freshwater, i.e., Zn2+ ions may modulate the effects of the selected GNPs (40 nm, citrate, and PVP capped). Preliminary toxicity results revealed that gold nanoparticles were highly toxic in comparison to zinc ions alone. A significant modulation in the toxicity of Zn ions was not noticed in the presence of GNPs. In contrast, zinc ions minimized the toxicity produced by GNPs (both CIT-37 and PVP-37), despite its individual toxicity. Approximately, about 42, 33, and 25% toxicity reduction was noted at 0.05-, 0.5-, and 5-mg L−1 Zn ions, respectively, for CIT-37 GNPs, while 31% (0.05 mg L−1), 24% (0.5 mg L−1), and 9% (5 mg L−1) of toxicity reduction were noted for PVP-37 GNPs. Maximum toxicity reduction was seen at 0.05 mg L−1 of Zn ions. Abbott modeling substantiated antagonistic effects offered by Zn2+ ions on GNPs. Stability and sedimentation data revealed that the addition of zinc ions gradually induced the aggregation of NPs and in turn significantly reduced the toxicity of GNPs. Thus, the naturally existing ions like Zn2+ have an ability to modulate the toxicity of GNPs in a real-world environment scenario.

Nanocomposites of polymethyl-methacrylate (PMMA) have gained high attention owing to their extensive applications as antibacterial agents. The antibacterial activities of Ag and TiO2 nanoparticles are well established. This study intended to differentiate the antibacterial activities exhibited by PMMA/TiO2/Ag nanocomposite, towards bacterial consortium and single dominant bacterial isolates from packaged drinking water. A silver nanoparticle dose-dependent decline in cell viability of consortium and individual isolates was compared under UVC and dark conditions to evaluate the antibacterial activity of the nanocomposite. To corroborate with the viability results, oxidative stress & cell permeability was also assessed under similar conditions. Surface characterization of PMMA/TiO2/Ag nanocomposite was performed by FTIR, AFM, and SEM analyses after interaction with the bacteria. The PMMA/TiO2/Ag nanocomposite showed enhanced antibacterial activity against single bacterial isolate compared to the consortium. The outcomes from the study with PMMA/TiO2/Ag nanocomposite necessitate relooking at the test design for assessment of antibacterial effects in real conditions incorporating the impact on the consortium of microorganisms instead of individual strains.

This paper presents a high-speed Vedic multiplier based on the Urdhva Tiryagbhyam sutra of Vedic mathematics that incorporates a novel adder based on Quaternary Signed digit number system. Three operations are inherent in multiplication: partial products generation, partial products reduction and addition. A fast adder architecture therefore greatly enhances the speed of the overall process. A Quaternary logic adder architecture is proposed that works on a hybrid of binary and quaternary number systems. A given binary string is first divided into quaternary digits of 2 bits each followed by parallel addition reducing the carry propagation delay. The design doesn't require a radix conversion module as the sum is directly generated in binary using the novel concept of an adjusting bit. The proposed multiplier design is compared with a Vedic multiplier based on multi voltage or multi value logic [MVL], Vedic Multiplier that incorporates a QSD adder with a conversion module for quaternary to binary conversion, Vedic multiplier that uses Carry Select Adder and a commonly used fast multiplication mechanism such as Booth multiplier. All these designs have been developed using Verilog HDL and synthesized by Synopsys Design Compiler. They have been realized using the open source NAN gate 15nm technology library. The proposal shows a maximum of 88.75% speed improvement with respect to Multi Value logic based 128x128 Vedic multiplier while the minimum is 17.47%.

This paper proposes a fast, purely combinational implementation of a divider, based on the Dhwajanka Sutra of Vedic mathematics. Vedic mathematics offers algorithms that are computationally efficient over conventional arithmetic algorithms. Dhwajanka Sutra has been chosen as it is an algorithm efficient for all possible cases, unlike other sutras for division (Nikhilam and Paravartya) which are case specific. The simplicity of the Vedic algorithm implemented in combinational form has reduced computation time significantly The proposed design is compared with existing divider architectures implemented on an FPGA namely Non-restoring Algorithm based Divider, Vedic Divider (Paravartya Algorithm), Vedic Divider (Nikhilam Algorithm), Decimal Divider based on Newton Raphson algorithm, Decimal Divider based on SRT algorithm and Combination divider algorithms. The proposed vedic divider shows a maximum of 273.72% speed improvement while the minimum is 99.95%. The results have been validated using the Xilinx ISE Design Suite 14.7, on the Virtex5 (xc5vlx20T-2ff323) FPGA Target Technology and the design has been implemented in Verilog.

P25 TiO2 nanoparticles majorly used in cosmetic products have well known detrimental effects towards the aquatic environment. In a freshwater ecosystem, Chlorella and Scenedesmus are among the most commonly found algal species frequently used to study the effects of metal oxide nanoparticles. A comparative study has been conducted herein to investigate differences in the toxic effects caused by these nanoparticles towards the two algae species. The three different concentrations of P25 TiO2 NPs (0.01, 0.1 & 1μg/mL, i.e., 0.12, 1.25 and 12.52μM) were selected to correlate surface water concentrations of the nanoparticles, and filtered and sterilized fresh water medium was used throughout this study. There was significant increase (p

The current study was aimed to explore the differential effects on Gram-positive and Gram-negative freshwater sediment bacterial isolates upon exposure to nano-particles and bulk particles of Al2O3 at low concentrations (0.25, 0.5, and 1 mg/L). The Gram-negative Pseudomonas aeruginosa was more susceptible to both the nano-forms and bulk forms than the Gram-positive Bacillus altitudinis. The generation of reactive oxygen species (ROS) and release of lipopolysaccharide due to membrane damage were dependent on the dose of nano-Al2O3. The Fourier transform infrared spectroscopy (FT-IR) studies confirmed the attachment of nano-Al2O3 on bacterial cells, which may lead to subsequent changes in the cell membrane composition and integrity. Internalization of nano-Al2O3 was estimated to be more for P. aeruginosa than for B. altitudinis cells. As a role of defense mechanism, the biofilm formation and production of extracellular polymeric substances (EPSs; polysaccharide and protein) were increased with respect to the concentration of toxicant. Nano-Al2O3 was estimated to cause more DNA damage than the bulk particles in both Gram-positive and Gram-negative bacterial strains.