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In many rapidly urbanizing and industrializing countries, atmospheric pollution causes severe environmental problems and compromises the health of humans and ecosystems. Atmospheric emissions, which encompass gases and particulate matter, can be transported back to the earth's surface through atmospheric deposition. Atmospheric deposition supplies chemical species that can serve as nutrients and/or toxins to aquatic ecosystems, resulting in wide-ranging responses of aquatic organisms. Among the aquatic organisms, phytoplankton is the basis of the aquatic food web and is a key player in global primary production. Atmospheric deposition alters nutrient availability and thus influences phytoplankton species abundance and composition. This review provides a comprehensive overview of the physiological responses of phytoplankton resulting from the atmospheric deposition of trace metals, nitrogen-containing compounds, phosphorus-containing compounds, and sulfur-containing compounds in particulate matter into aquatic ecosystems. Knowledge gaps and critical areas for future studies are also discussed.

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The increased usage of titanium dioxide nanoparticles (nTiO2) in consumer products has led to their prevalence in freshwater systems. Nanoplastics, a secondary pollutant, can significantly influence the toxic effects of nTiO2 in freshwater organisms. The present study investigates the role of fluorescent nanoplastics (FNPs) in modifying the harmful effects of P25 nTiO2 in freshwater algae Scenedesmus obliquus. Three different concentrations of nTiO2, 0.025, 0.25, and 2.5 mg/L, were mixed with 1 mg/L of the FNPs to perform the mixture toxicity experiments. The presence of the FNPs in the mixture increased the toxicity of nTiO2 significantly. A significant increment in the oxidative stress parameters like total ROS, superoxide (O2∎-), and hydroxyl radical generation was observed for the mixture of nTiO2 with the FNPs in comparison with their individual counterparts. The lipid peroxidation, and the antioxidant enzyme activities in the algal cells correlated well with the reactive species generation results. The treatments with the binary mixture resulted in notable decrease in the esterase activity in the algal cells. The mixture toxicity results were further validated with Abbott's independent action model. Additionally, optical microscopic analysis and FTIR analysis were performed to study the morphological and surface chemical changes in the algae. This study demonstrated that the FNPs played a key role in enhancing the toxicity of nTiO2 in freshwater algae.

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Increasing usage of both nanomaterials and pharmaceuticals and their unabated release to the marine ecosystem pose a serious concern nowadays. The toxicity of the mixture of TiO2 NPs and tetracycline (TC) in the marine species are not very well covered in prior literature. The current study explores the joint toxic effects of TiO2 NPs and TC in a simulated marine food chain: Chlorella sp. and Artemia salina. Chlorella sp. was interacted with pristine TiO2 NPs (0.05, 05, and 5 mg/L), TC (0.5 mg/L), and their combinations for 48 h. The toxicity induced in Chlorella sp. by pristine TiO2 NPs through oxidative stress and chloroplast damage was not significantly changed in the presence of TC. Principal component analysis for the toxicity parameters revealed a strong association between growth inhibition and adsorption/internalization. In the second trophic level (A. salina), the waterborne exposure of TC additively increased the toxicity of TiO2 NPs. Both adsorption and degradation played a major role in the removal of TC from the suspension, resulting in additive toxic effects in both Chlorella sp. and A. salina. Compared to the waterborne exposure, the foodborne exposure of TiO2 NPs and TC induced lesser toxic effects owing to reduced uptake and accumulation in A. salina. Biomagnification results indicate that the dietary transfer of TiO2 NPs and TC does not pose a serious environmental threat in this two-level marine food chain.

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The rising use of contaminants such as nanoparticles and microplastics has taken a heavy toll on the marine environment. However, their combined toxic effects on the species across various trophic levels remain quite unexplored. The aim of this study was to explore the effects of three surface-functionalized (carboxylated, plain, and aminated) polystyrene microplastics on nano-TiO2 toxicity across two trophic levels containing Chlorella sp. as the prey and Artemia salina as the predator. The experiments carried out on Chlorella sp. include the toxicity assessment, oxidative stress determination, and uptake of nano-TiO2 (both in the presence and absence of microplastics). Results revealed that the aminated and plain polystyrene microplastics enhanced nano-TiO2 toxicity, while carboxylated microplastics decreased the toxic effects in Chlorella sp. On the other hand, toxicity assessment in Artemia salina was carried out using two different modes of exposure: aqueous and dietary routes. The aqueous route involving the direct exposure of nano-TiO2 and microplastics indicated greater toxicity, uptake, and accumulation in Artemia salina than the dietary route of exposure. Since dietary exposure decreased the toxicity, uptake, and accumulation of nano-TiO2, no change (p > 0.05) in the biomagnification factors of nano-TiO2 was noted for all the test concentrations of nano-TiO2 combined with and without microplastics. The computed values were less than 1, indicating negligible transfer of nano-TiO2 from Chlorella sp. to Artemia salina. Overall, the study highlights the two-level trophic toxicity and the transfer potential of nano-TiO2 under the influence of different microplastics.

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Micro/nanoplastics are ubiquitous in the environment and cause pollution of the aquatic ecosystem, in particular, which is a serious concern worldwide. Micro/nanoplastics can act as a vector for multiple co-contaminants that co-exist in the aquatic environment. Apart from micro/nanoplastics, nanomaterials and pharmaceuticals are other emerging contaminants that can also raise severe problems. Thus, in this review, the physicochemical interactions occurring between micro/nanoplastics and nanomaterials and pharmaceuticals and the factors (chemical and environmental) affecting the sorption efficiency of nanomaterials and pharmaceuticals have been addressed. Furthermore, the influence of micro/nanoplastics on the bioavailability and toxic effects of nanomaterials and pharmaceuticals on both freshwater and marine species has been highlighted. Additional focus has also been given to study the mechanism of toxicity of the micro/nanoplastics-nanomaterials and pharmaceuticals complex on the different species of different trophic levels. Finally, this review addresses the knowledge gaps and provides insights into the future research strategies to better understand the interactive mechanisms between the binary contaminants and also the toxicity mechanisms of micro/nanoplastics and nanomaterials and pharmaceuticals.

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There has been a significant increased concern of the impact of the toxicity of multiple contaminants in the marine environment. Thus, this study was aimed at determining whether the interaction between nano-TiO2 and Cr(VI) would modulate their toxic effects with the marine crustacean, Artemia salina. Nano-TiO2 agglomerated in artificial sea water (ASW) and readily formed micron-sized particles that settled down in the medium. The addition of Cr(VI) to nano-TiO2 aggravated their agglomeration through sorption of Cr(VI) onto nano-TiO2. This was reflected by a decrease in the residual concentration of Cr in the suspension. Acute toxicity tests performed using pristine nano-TiO2 (0.25, 0.5, 1, 2, and 4 mg/L) and Cr(VI) (0.125, 0.25, 0.5, and 1 mg/L) displayed a concentration dependent rise in the mortality of Artemia salina. To examine the effects of mixtures of nano-TiO2 and Cr(VI) on Artemia salina, two groups of experiments were designed. The former group studied the toxic effect of nano-TiO2 (0.5, 1, 2, and 4 mg/L) with a fixed concentration (0.125 mg/L) of Cr(VI). While the latter group studied the toxicity of Cr(VI) (0.25, 0.5, and 1 mg/L) with a fixed concentration (0.25 mg/L) of nano-TiO2. The toxic effects of nano-TiO2 was not significantly reduced at a fixed concentration of Cr(VI) but in contrast, a significant reduction in the Cr(VI) toxicity by fixed concentration of nano-TiO2 was observed. Toxicity data was well supported by an independent action model that proved the mode of action between nano-TiO2 and Cr(VI) to be antagonistic. Furthermore, ROS generation and measurement of antioxidant enzyme activities were also in line with toxicity results. From this study, the modification of Cr(VI) toxicity at fixed concentration of nano-TiO2 could have a huge impact on the reduction in Cr(VI) toxicity across trophic levels.

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Pollutants such as n-TiO2 and tetracycline enter the marine environment through various sources starting from their production until disposal. Hence, it is vital to determine the interactive effect of one pollutant with the other when they coexist in the environment. In the present study, the effect of antibiotic - tetracycline (TC) on the toxicity of P25 n-TiO2 was studied with marine microalgae, Chlorella sp. The impact of TC (1 mg L-1) on five different concentrations of n-TiO2 (0.25, 0.5, 1, 2 and 4 mg L-1) under both visible and UV-A illuminations was evaluated. Effective diameter of n-TiO2 in ASW at 0th h increased from 690.69 ±â€¯19.55 nm (0.25 mg L-1) to 1183.04 ±â€¯37.10 nm (0.25 mg L-1 + 1 mg L-1) and 971.51 ±â€¯14.61 nm (4 mg L-1) to 1324.12 ±â€¯11.59 nm (4 mg L-1 + 1 mg L-1) in presence of TC. A significant increase in the toxicity of 4 mg L-1 n-TiO2 upon the addition of TC (68.16 ±â€¯0.37% under visible and 80.21 ±â€¯0.3% under UV-A condition) was observed. No significant difference in toxicity was observed between visible and UV-A illuminations. Further the toxicity data was corroborated through the measurement of oxidative stress and antioxidant enzyme activities. Independent action model showed antagonistic effect for lower concentrations of n-TiO2 and additive effect for higher concentrations of n-TiO2 when present in mixture with TC under both illuminations. For the higher mixture concentration of 4 mg L-1 n-TiO2 and 1 mg L-1 TC, the percentage TC removal was about 55.29% and 30% and the corresponding TOC removal was found to be 54.29% and 31.04% under visible and UV-A illuminations respectively. The site of ROS generation in Chlorella sp. was identified with electron transfer chain inhibitors. Both mitochondria and chloroplast acted as the site for the ROS generation in Chlorella sp. The SEM images of the algal cells upon exposure to n-TiO2 and mixture revealed the aggregation of cells and distortion of cell membrane.

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Titanium dioxide nanoparticles (TiO2 NPs) find applications in our day-to-day life because of unique physicochemical properties. Their release into the aquatic environment poses a possible risk to the organisms. However, the continuing exposure of NPs might reduce their bioavailability to marine organisms owing to aggregation and sedimentation in the aqueous systems thus significantly reducing their toxic impact. In this regard, the present study investigates the effect of continuous exposure of TiO2 NPs to marine microalgae Chlorella sp. under UV-A irradiation through "tanks in series" mode of experiments. In a three-cycle experiment, concentration of TiO2 NPs in the first cycle was fixed at 62.6 µM, and the interacted nanoparticles was subsequently exposed to fresh batches of algae in the next two cycles. After the interaction, the NPs underwent severe aggregation (mean hydrodynamic diameter 3000 ±â€¯18.2 nm after cycle I) leading to gravitational settling in the medium and thus decreased bioavailability. The aggregation can be attributed to interactions between the particles themselves (homo-aggregation) further aggravated by the presence of the algal cells (hetero-aggregation). Cellular viability after cycle I was found to be only 24.2 ±â€¯2.5%, and it was enhanced to 96.5 ±â€¯2.8% after the cycle III in the course of continuous exposure. The results were validated with estimation of oxidative stress markers such as intracellular ROS (total ROS, superoxide and hydroxyl radicals) and LPO after each cycle of exposure. The continuing decrease in the EPS across the cycles further confirmed the diminishing toxicity of the NPs.

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The use of P25 TiO2 NPs in consumer products, their release, and environmental accumulation will have harmful effects on the coastal ecosystems. The sensitivity to TiO2 NPs may vary depending on the structural property and physiological mechanism of algal species. Therefore, the present study investigates the differences in sensitivity of two marine algae, Dunaliella salina and Chlorella sp., towards P25 TiO2 NPs. Among the two species, Chlorella sp. was more sensitive to TiO2 NPs than Dunaliella salina. The different working concentrations of TiO2 NPs, 0.1, 1, and 10 mg L-1, were selected based on the EC50 value. The EC50 value of TiO2 NPs for Dunaliella salina was found to be 1.8 and 13.3 mg L-1 under UV-A and dark conditions, respectively. The EC50 value of TiO2 NPs for Chlorella sp. was found to be 1.6 and 5.0 mg L-1 under UV-A and dark conditions, respectively. The decrease in cell viability was significantly higher for Chlorella sp. compared to Dunaliella salina at all concentrations except 0.1 mg L-1. The cellular viability data was in correlation with the oxidative stress markers such as total ROS and LPO. A concentration-dependent increase in ROS and lipid peroxidation was noted under UV-A exposure, which was higher in Chlorella sp. compared to Dunaliella salina. The decrease in the SOD activity with NP concentration was more in Dunaliella salina than Chlorella sp. under both conditions, whereas Chlorella sp. showed increased CAT activity with increasing concentration. The uptake of TiO2 NPs was more in Chlorella sp. than Dunaliella salina.

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Increased utilization of titanium dioxide nanoparticles (TiO2 NPs) for commercial as well as industrial purposes resulted in the accumulation of nanoparticles in the marine system. Microplastics being an emerging secondary pollutant in the marine ecosystem have an impact on the toxic effects of TiO2 NPs which has not been evaluated up to date. So it is important to assess the toxic effects of both these pollutants on the marine environment. The present study examines the impact of differently functionalized microplastics on the toxic effects of P25 TiO2 NPs to marine algae Chlorella sp. The tendency of nanoparticles to undergo aggregation in artificial seawater was observed with increase in time. The median effective concentration for TiO2 NPs was found to be 81 µM which indicates higher toxic effects of NPs toward algae. In contrast, microplastics irrespective of their difference in functionalization had minimal toxic effect of about 15% at their higher concentration tested, 1000 mg L-1. Plain and aminated polystyrene microplastics enhanced the TiO2 NPs toxicity which was further validated with oxidative stress determination studies like reactive oxygen species and lipid peroxidation assays. Negatively charged carboxylated polystyrene microplastics decreased the TiO2 NPs toxicity with possible hetero-aggregation between TiO2 NPs and microplastics in the system. The toxicity data obtained for the mixture was further corroborated with Abbott's mathematical model.

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The recent increase in nanoparticle (P25 TiO2 NPs) usage has led to concerns regarding their potential implications on environment and human health. The food chain is the central pathway for nanoparticle transfer from lower to high trophic level organisms. The current study relies on the investigation of toxicity and trophic transfer potential of TiO2 NPs from marine algae Dunaliella salina to marine crustacean Artemia salina. Toxicity was measured in two different modes of exposure such as waterborne (exposure of TiO2 NPs to Artemia) and dietary exposure (NP-accumulated algal cells are used to feed the Artemia). The toxicity and accumulation of TiO2 NPs in marine algae D. salina were also studied. Artemia was found to be more sensitive to TiO2 NPs (48h LC50 of 4.21mgL-1) as compared to marine algae, D. salina (48h LC50 of 11.35mgL-1). The toxicity, uptake, and accumulation of TiO2 NPs were observed to be more in waterborne exposure as compared to dietary exposure. Waterborne exposure seemed to cause higher ROS production and antioxidant enzyme (SOD and CAT) activity as compared to dietary exposure of TiO2 NPs in Artemia. There were no observed biomagnification (BMF) and trophic transfer from algae to Artemia through dietary exposure. Histopathological studies confirmed the morphological and internal damages in Artemia. This study reiterates the possible effects of the different modes of exposure on trophic transfer potential of TiO2 NPs and eventually the consequences on aquatic environment.

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Clinical use of camptothecin (CPT) is hindered due to its poor water and oil solubility, active lactone ring instability and non-targeted toxicity. Recently we reported formulation of camptothecin microemulsions with increased solubility for the improved treatment of breast cancer. In this research chitosan stabilized camptothecin nanoemulsions (CHI-CPT-NEs) were formulated improve the cancer targeting efficiency of CPT. The developed NEs were characterized for their droplet size distribution, stability in plasma and evaluated for in-vitro drug release, in-vivo targeting potential, in-vitro hemolytic potential, cytotoxicity, genotoxicity and in-vivo biodistribution. The CHI-CPT-NEs showed uniform droplet size distribution, extended drug release (61.65±1.57% at 24h), tolerable hemolytic potential (16.4±1.4%), significant cytotoxicity (178±4.3ng/ml) against MCF-7 cancer cells and low DNA damage to lymphocytes. In-vivo biodistribution study conducted in 4T1-breast tumor xenograft BALB/c mice showed that 2495.22±174.66ng/gm of camptothecin was passively targeted to breast cancer by CHI-CPT-NEs compared to the non-stabilized nanoemulsion (1677.58±134.21ng/gm). Thus, passive targeting of developed CHI-CPT-NEs may provide a promising approach for the efficient breast cancer therapy.

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Choline, a type of Vitamin B, is an important nutrient in the human body and is involved in key metabolic pathways. Abnormal levels of choline leads to diseased conditions. The levels of choline and its associated compounds are found to be elevated in triple negative breast cancer (TNBC) patients. The choline level ranges from 0.4 to 4.9mmol/kg in TNBC. Thus the detection of choline levels in cells can aid in diagnosing breast cancer. The present work aims to develop a nano-interfaced electrochemical biosensor for the rapid detection of choline in cancer cells. For electrochemical detection, glassy carbon electrode coated with a zinc oxide nano-interface was used as the working electrode. Zinc oxide synthesized by hydrothermal method was characterized using SEM and XRD. The choline oxidase (ChOx) enzyme was immobilized on the nano-interface by drop-casting. Choline oxidase (ChOx) converts choline to betaine and H2O2 in the presence of oxygen. The H2O2 produced was determined amperometrically. The amount of H2O2 produced is directly proportional to concentration of choline present. The sensitivity, selectivity, stability and concentration studies were carried out and quantification of choline in TNBC was also carried out. The results demonstrate that this biosensor has the potential to be developed as a clinical tool for breast cancer detection.

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