Biosynthesis of photostable CdS quantum dots by UV-resistant psychrotolerant bacteria isolated from Union Glacier, Antarctica.

BACKGROUND: Quantum Dots (QDs) are fluorescent nanoparticles with exceptional optical and optoelectronic properties, finding widespread utility in diverse industrial applications. Presently, chemically synthesized QDs are employed in solar cells, bioimaging, and various technological domains. However, many applications demand QDs with prolonged lifespans under conditions of high-energy radiation. Over the past decade, microbial biosynthesis of nanomaterials has emerged as a sustainable and cost-effective process. In this context, the utilization of extremophile microorganisms for synthesizing QDs with unique properties has recently been reported. RESULTS: In this study, UV-resistant bacteria were isolated from one of the most extreme environments in Antarctica, Union Glacier at the Ellsworth Mountains. Bacterial isolates, identified through 16 S sequencing, belong to the genera Rhodococcus, Pseudarthrobacter, and Arthrobacter. Notably, Rhodococcus sp. (EXRC-4 A-4), Pseudarthrobacter sp. (RC-2-3), and Arthrobacter sp. (EH-1B-1) tolerate UV-C radiation doses ≥ 120 J/m². Isolated UV-resistant bacteria biosynthesized CdS QDs with fluorescence intensities 4 to 8 times higher than those biosynthesized by E. coli, a mesophilic organism tolerating low doses of UV radiation. Transmission electron microscopy (TEM) analysis determined QD sizes ranging from 6 to 23 nm, and Fourier-transform infrared (FTIR) analysis demonstrated the presence of biomolecules. QDs produced by UV-resistant Antarctic bacteria exhibit high photostability after exposure to UV-B radiation, particularly in comparison to those biosynthesized by E. coli. Interestingly, red fluorescence-emitting QDs biosynthesized by Rhodococcus sp. (EXRC-4 A-4) and Arthrobacter sp. (EH-1B-1) increased their fluorescence emission after irradiation. Analysis of methylene blue degradation after exposure to irradiated QDs biosynthesized by UV-resistant bacteria, indicates that the QDs transfer their electrons to O2 for the formation of reactive oxygen species (ROS) at different levels. CONCLUSIONS: UV-resistant Antarctic bacteria represent a novel alternative for the sustainable generation of nanostructures with increased radiation tolerance-two characteristics favoring their potential application in technologies requiring continuous exposure to high-energy radiation.

Acetogenic bacteria utilize light-driven electrons as an energy source for autotrophic growth.

Acetogenic bacteria use cellular redox energy to convert CO2 to acetate using the Wood-Ljungdahl (WL) pathway. Such redox energy can be derived from electrons generated from H2 as well as from inorganic materials, such as photoresponsive semiconductors. We have developed a nanoparticle-microbe hybrid system in which chemically synthesized cadmium sulfide nanoparticles (CdS-NPs) are displayed on the cell surface of the industrial acetogen Clostridium autoethanogenum The hybrid system converts CO2 into acetate without the need for additional energy sources, such as H2, and uses only light-induced electrons from CdS-NPs. To elucidate the underlying mechanism by which C. autoethanogenum uses electrons generated from external energy sources to reduce CO2, we performed transcriptional analysis. Our results indicate that genes encoding the metal ion or flavin-binding proteins were highly up-regulated under CdS-driven autotrophic conditions along with the activation of genes associated with the WL pathway and energy conservation system. Furthermore, the addition of these cofactors increased the CO2 fixation rate under light-exposure conditions. Our results demonstrate the potential to improve the efficiency of artificial photosynthesis systems based on acetogenic bacteria integrated with photoresponsive nanoparticles.

A novel insight into mechanism of derangement of coagulation balance: interactions of quantum dots with coagulation-related proteins.

BACKGROUND: Quantum dots (QDs) have gained increased attention for their extensive biomedical and electronic products applications. Due to the high priority of QDs in contacting the circulatory system, understanding the hemocompatibility of QDs is one of the most important aspects for their biosafety evaluation. Thus far, the effect of QDs on coagulation balance haven't been fully understood, and limited studies also have yet elucidated the potential mechanism from the perspective of interaction of QDs with coagulation-related proteins. RESULTS: QDs induced the derangement of coagulation balance by prolonging the activated partial thromboplastin time and prothrombin time as well as changing the expression levels of coagulation and fibrinolytic factors. The contact of QDs with PTM (prothrombin), PLG (plasminogen) and FIB (fibrinogen) which are primary coagulation-related proteins in the coagulation and fibrinolysis systems formed QDs-protein conjugates through hydrogen-bonding and hydrophobic interaction. The affinity of proteins with QDs followed the order of PTM > PLG > FIB, and was larger with CdTe/ZnS QDs than CdTe QDs. Binding with QDs not only induced static fluorescence quenching of PTM, PLG and FIB, but also altered their conformational structures. The binding of QDs to the active sites of PTM, PLG and FIB may promote the activation of proteins, thus interfering the hemostasis and fibrinolysis processes. CONCLUSIONS: The interactions of QDs with PTM, PLG and FIB may be key contributors for interference of coagulation balance, that is helpful to achieve a reliable and comprehensive evaluation on the potential biological influence of QDs from the molecular level.

Formation of cadmium sulfide nanoparticles mediates cadmium resistance and light utilization of the deep-sea bacterium Idiomarina sp. OT37-5b.

Heavy metal is one of the major factors threatening the survival of microorganisms. Here, a deep-sea bacterium designated Idiomarina sp. OT37-5b possessing strong cadmium (Cd) tolerance was isolated from a typical hydrothermal vent. Both the Cd-resistance and removal efficiency of Idiomarina sp. OT37-5b were significantly promoted by the supplement of cysteine and meanwhile large amount of CdS nanoparticles were observed. Production of H2 S from cysteine catalysed by methionine gamma-lyase was further demonstrated to contribute to the formation of CdS nanoparticles. Proteomic results showed the addition of cysteine effectively enhanced the efflux of Cd, improved the activities of reactive oxygen species scavenging enzymes, and thereby boosted the nitrogen reduction and energy production of Idiomarina sp. OT37-5b. Notably, the existence of CdS nanoparticles obviously promoted the growth of Idiomarina sp. OT37-5b when exposed to light, indicating this bacterium might grab light energy through CdS nanoparticles. Proteomic analysis revealed the expression levels of essential components for light utilization including electron transport, cytochrome complex and F-type ATPase were significantly up-regulated, which strongly suggested the formation of CdS nanoparticles promoted light utilization and energy production. Our results provide a good model to investigate the uncovered mechanisms of self-photosensitization of nonphotosynthetic bacteria for light-to-chemical production in the deep biosphere.

Surface-Modified Colloid CdTe/CdS Quantum Dots by a Biocompatible Thiazolidine Derivative as Promising Platform for Immobilization of Glucose Oxidase: Application to Fluorescence Sensing of Glucose.

This work focuses on the synthesis of novel modified core-shell CdTe/CdS quantum dots (QDs) and develops as a fluorescence sensor for glucose determination. The (E)-2,2'-(4,4'-dioxo-2,2'-dithioxo-2H,2'H-[5,5'-bithiazolylidene]-3,3'(4H,4'H)-diyl)bis(3- mercaptopropanoic acid) (DTM) as a new derivative of thiazolidine was synthesized and characterized and used to surface-modification of CdTe/CdS QDs. DTM-capped CdTe/CdS QDs used to immobilization of glucose oxidase (GOD). The intensity fluorescence emission of the CdSe/CdS-DTM/GOD is highly sensitive to the concentration of H2O2 as a byproduct of the catalytic oxidation of glucose. The experimental results showed that the quenched fluorescence was proportional to the glucose concentration within the range of 10 nM-0.32 µM under optimized experimental conditions. The limit of detection of this system was found to be 4.3 nM. Compared with most of the existing methods, this newly developed system possesses many advantages, including simplicity, low cost, and good sensitivity.

In vitro toxicity assessment of fungal-synthesized cadmium sulfide quantum dots using bacteria and seed germination models.

There is currently controversy over the use of quantum dots (QDs) in biological applications due to their toxic effects. Therefore, the purpose of the present study was to evaluate the toxic effect of chemical and biogenic (synthesized by Fusarium oxysporum f. sp. lycopersici) cadmium sulfide quantum dots (CdSQDs) using a bacterial model of Escherichia coli and sprouts of Lactuca sativa L. with the aim to foresee its use in the near future in biological systems. Physicochemical properties of both types of CdSQDs were determined by TEM, XRD, zeta potential and fluorescence spectroscopy. Both biogenic and chemical CdSQDs showed agglomerates of spherical CdSQDs with diameters of 4.14 nm and 3.2 nm, respectively. The fluorescence analysis showed a band around 361 nm in both CdSQDs, the zeta potential was -1.81 mV for the biogenic CdSQDs and -5.85 mv for the chemical CdSQDs. Results showed that chemical CdSQDs, presented inhibition in the proliferation of E. coli cell in a dose-dependent manner, unlike biogenic CdSQDs, that only at its highest concentration showed an antibacterial activity. Also, it was observed that after incubation with chemical and biogenic CdSQDs of L. sativa L. seeds, only the biogenic CdSQDs showed no inhibition on seed germination. In summary, our results suggest that the production route has a significant effect on the toxicity of QDs; in addition, it seems that the biological coating of the CdSQDs from F. oxysporum f. sp. lycopersici inhibit their toxic effect on bacterial strains and plant seeds.

Enhanced Light-Driven Hydrogen Production by Self-Photosensitized Biohybrid Systems.

Storage of solar energy as hydrogen provides a platform towards decarbonizing our economy. One emerging strategy for the production of solar fuels is to use photocatalytic biohybrid systems that combine the high catalytic activity of non-photosynthetic microorganisms with the high light-harvesting efficiency of metal semiconductor nanoparticles. However, few such systems have been tested for H2 production. We investigated light-driven H2 production by three novel organisms, Desulfovibrio desulfuricans, Citrobacter freundii, and Shewanella oneidensis, self-photosensitized with cadmium sulfide nanoparticles, and compared their performance to Escherichia coli. All biohybrid systems produced H2 from light, with D. desulfuricans-CdS demonstrating the best activity overall and outperforming the other microbial systems even in the absence of a mediator. With this system, H2 was continuously produced for more than 10 days with a specific rate of 36 µmol gdcw-1 h-1 . High apparent quantum yields of 23 % and 4 % were obtained, with and without methyl viologen, respectively, exceeding values previously reported.

Defining Intermediates of Nitrogenase MoFe Protein during N2 Reduction under Photochemical Electron Delivery from CdS Quantum Dots.

Coupling the nitrogenase MoFe protein to light-harvesting semiconductor nanomaterials replaces the natural electron transfer complex of Fe protein and ATP and provides low-potential photoexcited electrons for photocatalytic N2 reduction. A central question is how direct photochemical electron delivery from nanocrystals to MoFe protein is able to support the multielectron ammonia production reaction. In this study, low photon flux conditions were used to identify the initial reaction intermediates of CdS quantum dot (QD):MoFe protein nitrogenase complexes under photochemical activation using EPR. Illumination of CdS QD:MoFe protein complexes led to redox changes in the MoFe protein active site FeMo-co observed as the gradual decline in the E0 resting state intensity that was accompanied by an increase in the intensity of a new "geff = 4.5" EPR signal. The magnetic properties of the geff = 4.5 signal support assignment as a reduced S = 3/2 state, and reaction modeling was used to define it as a two-electron-reduced "E2" intermediate. Use of a MoFe protein variant, ß-188Cys, which poises the P cluster in the oxidized P+ state, demonstrated that the P cluster can function as a site of photoexcited electron delivery from CdS to MoFe protein. Overall, the results establish the initial steps for how photoexcited CdS delivers electrons into the MoFe protein during reduction of N2 to ammonia and the role of electron flux in the photochemical reaction cycle.

Photo-biohydrogen Production by Photosensitization with Biologically Precipitated Cadmium Sulfide in Hydrogen-Forming Recombinant Escherichia coli.

An inorganic-biological hybrid system that integrates features of both stable and efficient semiconductors and selective and efficient enzymes is attractive for facilitating the conversion of solar energy to hydrogen. In this study, we aimed to develop a new photocatalytic hydrogen-production system based on Escherichia coli whole-cell genetically engineered as a biocatalysis for highly active hydrogen formation. The photocatalysis part was obtained by bacterial precipitation of cadmium sulfide (CdS), which is a visible-light-responsive semiconductor. The recombinant E. coli cells were sequentially subjected to CdS precipitation and heterologous [FeFe]-hydrogenase synthesis to yield a CdS@E. coli hybrid capable of light energy conversion and hydrogen formation in a single cell. The CdS@E. coli hybrid achieved photocatalytic hydrogen production with a sacrificial electron donor, thus demonstrating the feasibility of our system and expanding the current knowledge of photosensitization using a whole-cell biocatalyst with a bacterially precipitated semiconductor.

Consequences of surface coatings and soil ageing on the toxicity of cadmium telluride quantum dots to the earthworm Eisenia fetida.

The bioaccumulation potential and toxic effects of engineered nanomaterials (ENMs) to earthworms are poorly understood. Two studies were conducted following OECD TG 222 on Eisenia fetida to assess the effects of CdTe QDs with different coatings and soil ageing respectively. Earthworms were exposed to carboxylate (COOH), ammonium (NH4+), or polyethylene glycol (PEG) coated CdTe QDs, or a micron scale (bulk) CdTe material, at nominal concentrations of 50, 500 and 2000 mg CdTe QD kg-1 dry weight (dw) for 28 days in Lufa 2.2 soil. In the fresh soil study, earthworms accumulated similar amounts of Cd and Te in the CdTe-bulk exposures, while the accumulation of Cd was higher than Te during the exposures to CdTe QDs. However, neither the total Cd, nor Te concentrations in the earthworms, were easily explained by the extractable metal fractions in the soil or particle dissolution. There were no effects on survival, but some retardation of growth was observed at the higher doses. Inhibition of Na+/K+-ATPase activity with disturbances to tissue electrolytes, as well as tissue Cu and Mn were observed, but without depletion of total glutathione in the fresh soil experiment. Additionally, juvenile production was the most sensitive endpoint, with estimated nominal EC50 of values >2000, 108, 65, 96 mg CdTe kg-1 for bulk, PEG-, COOH- and NH4+-coated CdTe QDs, respectively. In the aged soil study, the accumulation of Cd and Te was higher than in the fresh soil study in all CdTe QD exposures. Survival of the adult worms was reduced in the top CdTe-COOH and -NH4+ QD exposures by 55 ±â€¯5 and 60 ±â€¯25%, respectively; and with decreases in growth. The nominal EC50 values for juvenile production in the aged soil were 165, 88, 78 and 63 mg CdTe kg-1 for bulk, PEG-, COOH- and NH4+-coated CdTe QDs, respectively. In conclusion, exposure to nanoscale CdTe QDs, regardless of coating, caused more severe toxic effects that the CdTe bulk material and the toxicity increased after soil ageing. There were some coating-mediated effects, likely due to differences in the metal content and behaviour of the materials.

Biosynthesized CdS nanoparticles disturb E. coli growth through reactive oxygen production.

AIMS: E. coli is a widely known model organism for life science research, especially in modern bio-engineering and industrial microbiology. The goal of our current study is to understand the growth inhibitory mechanism of biosynthesized CdS nanoparticles on E. coli bacteria. MAIN METHODS: Characterization of Aspergillus foetidus mediated CdS nanoparticles has been confirmed by Zeta potential, AFM and HRTEM analyses. Furthermore, we investigated the contribution of reactive oxygen species (ROS) and subsequently lipid peroxidation on the growth of E. coli. FACS and fluorometric studies were used to know the ROS production upon CdS nanoparticle treatment. Lipid peroxidation measurement was studied by thiobarbituric acid (TBA) assay. KEY FINDINGS: The synthesized CdS nanoparticles are roughly spherical, poly-dispersed in nature and are in ~15 nm of size. Furthermore, our investigation confirmed that the cells treated with 200 µl of CdS nanoparticles produce about 50 % more ROS and about 5 times of lipid peroxidation over control cells. In addition, the number of E. coli colony survival and cell filamentation strongly depend on such lipid peroxidation caused by ROS, which actually produced due to the interaction with biosynthesized CdS nanoparticles in growth media. SIGNIFICANCE: The current research would be helpful for the mechanistic understanding of growth inhibition of E. coli by CdS nanoparticle. This may be useful for industrial applications of E. coli like bacteria.

Biodistribution and Systemic Effects in Mice Following Intravenous Administration of Cadmium Telluride Quantum Dot Nanoparticles.

Quantum dots (QDs) are engineered nanoparticles (NPs) of semiconductor structure that possess unique optical and electronic properties and are widely used in biomedical applications; however, their risks are not entirely understood. This study investigated the tissue distribution and toxic effects of cadmium telluride quantum dots (CdTe-QDs) in male BALB/c mice for up to 1 week after single-dose intravenous injections. CdTe-QDs were detected in the blood, lung, heart, liver, spleen, kidney, testis and brain. Most CdTe-QDs accumulated in the liver, followed by the spleen and kidney. At high doses, exposure to CdTe-QDs resulted in mild dehydration, lethargy, ruffled fur, hunched posture, and body weight loss. Histological analysis of the tissues, upon highest dose exposures, revealed hepatic hemorrhage and necrotic areas in the spleen. The sera of mice treated with high doses of CdTe-QDs showed significant increases in alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin levels, as well as a reduction in albumin. CdTe-QD exposure also led to a reduced number of platelets and elevated total white blood cell counts, including monocytes and neutrophils, serum amyloid A, and several pro-inflammatory cytokines. These results demonstrated that the liver is the main target of CdTe-QDs and that exposure to CdTe-QDs leads to hepatic and splenic injury, as well as systemic effects, in mice. By contrast, cadmium chloride (CdCl2), at an equivalent concentration of cadmium, appeared to have a different pharmacokinetic pattern from that of CdTe-QDs, having minimal effects on the aforementioned parameters, suggesting that cadmium alone cannot fully explain the toxicity of CdTe-QDs.

Toxicant Deposition and Transport in Alveolus: A Classical Density Functional Prediction.

The deposition and transport of toxicants on pulmonary surfactant are important processes in human health and medical care. We have introduced classical density functional theory (CDFT) to provide insight into this process. Nine typical toxicants in PM2.5 were considered, and their free energy and structural information have been examined. The free energy profile indicates that PbO, As2O3, and CdO are the three toxicants most easily deposited in the pulmonary alveolus, which is consistent with survey data. CuO appears to be the easiest toxicant to transport through the surfactant. Structural analysis indicates that the toxicants tend to pass through the surfactant with rotation. The configuration of the pulmonary surfactant was examined by extending our previous work to polymer systems, and it appears that both the configurational entropy and the direct interaction between the surfactant and the toxicant dominate the configuration of the pulmonary surfactant.

3D cellular spheroids as tools for understanding carboxylated quantum dot behavior in tumors.

BACKGROUND: Monolayer cell cultures have been considered the most suitable technique for in vivo cellular experiments. However, a lot of cellular functions and responses that are present in natural tissues are lost in two-dimensional cell cultures. In this context, nanoparticle accumulation data presented in literature are often not accurate enough to predict behavior of nanoparticles in vivo. Cellular spheroids show a higher degree of morphological and functional similarity to the tissues. METHODS: Accumulation and distribution of carboxylated CdSe/ZnS quantum dots (QDs), chosen as model nanoparticles, was investigated in cellular spheroids composed of different phenotype mammalian cells. The findings were compared with the results obtained in in vivo experiments with human tumor xenografts in immunodeficient mice. The diffusive transport model was used for theoretical nanoparticles distribution estimation. RESULTS: QDs were accumulated only in cells, which were localized in the periphery of cellular spheroids. CdSe/ZnS QDs were shown to be stable and inert; they did not have any side-effects for cellular spheroids formation. Penetration of QDs in both cellular spheroids and in vivo tumor model was limited. The mathematical model confirmed the experimental results: nanoparticles penetrated only 25µm into cellular spheroids after 24h of incubation. CONCLUSIONS: Penetration of negatively charged nanoparticles is limited not only in tumor tissue, but also in cellular spheroids. GENERAL SIGNIFICANCE: The results presented in this paper show the superior applicability of cellular spheroids to cell monolayers in the studies of the antitumor effect and penetration of nanomedicines.

Sulfate facilitates cadmium accumulation in leaves of Vicia faba L. at flowering stage.

Cadmium (Cd) is a toxic element, and is prevalent all over the world because of industrialization, mining, sewage sludge, or pesticide supply. Sulfur deficiency is also a frequent problem faced in agriculture. To date, information relating to effects of sulfate on Cd toxicity is still limited. To elucidate how sulfate affects Cd accumulation in faba bean, subcellular accumulation of Cd in leaves consisting of apoplastic washing fluid, symplastic fluid and the cell wall under deficient, sufficient and excess sulfate treatments were investigated in the present study. By using stable isotope of Cd (106Cd), we also traced Cd accumulation in young leaves at flowering stage from early and newly uptake of Cd in the same plants as affected by sulfate. We found that excess sulfate supply significantly increased newly uptake of Cd without affecting early uptake of Cd when compared with sufficient sulfate treatment, which resulted in enhanced total Cd in leaves by excess sulfate. Since newly uptake of Cd in leaves was from root uptake directly, we conclude that excess sulfate supply enhanced Cd originated from root uptake directly rather than re-translocation from old leaves, which is related to increased Cd accumulation in young leaves of faba bean. Subcellular analysis showed that the enhanced Cd by excess sulfate addition was a consequence of enhanced Cd in cell walls, while Cd accumulation in the apoplastic washing fluid and symplastic fluid were unchanged. The increased Cd by excess sulfate supply might be related to increased proportion of Cd speciation CdSO40 in the growth medium because of faster diffusion of CdSO40 than Cd2+. To test whether macronutrients, micronutrients, sulfate and non-protein thiol involved in cell wall-Cd accumulation as affected by sulfate, correlations of subcellular Cd with subcellular macronutrients, micronutrients, sulfate, and non-protein thiol were analyzed. We found that cell wall-Cd was negatively correlated with K and Ca concentrations, whereas cell wall-Cd was positively correlated with Cu and symplastic non-protein thiol concentrations. However, when compared with sufficient sulfate, excess sulfate decreased K concentration and increased symplastic non-protein thiol concentration without changing Ca and Cu concentrations. Based on those results, reduction of K concentration and enhancement of symplastic non-protein thiol concentration by sulfate supply might be a reason for increase of cell wall-Cd concentration. Taken together, increased Cd in cell walls of leaves by sulfate supply contributes to enhance Cd accumulation.

Comparative investigation of toxicity and bioaccumulation of Cd-based quantum dots and Cd salt in freshwater plant Lemna minor L.

The purpose of this study was to determine the toxicity of two different sources of cadmium, i.e. CdCl2 and Cd-based Quantum Dots (QDs), for freshwater model plant Lemna minor L. Cadmium telluride QDs were capped with two coating ligands: glutathione (GSH) or 3-mercaptopropionic acid (MPA). Growth rate inhibition and final biomass inhibition of L. minor after 168-h exposure were monitored as toxicity endpoints. Dose-response curves for Cd toxicity and EC50168h values were statistically evaluated for all sources of Cd to uncover possible differences among the toxicities of tested compounds. Total Cd content and its bioaccumulation factors (BAFs) in L. minor after the exposure period were also determined to distinguish Cd bioaccumulation patterns with respect to different test compounds. Laser-Induced Breakdown Spectroscopy (LIBS) with lateral resolution of 200µm was employed in order to obtain two-dimensional maps of Cd spatial distribution in L. minor fronds. Our results show that GSH- and MPA-capped Cd-based QDs have similar toxicity for L. minor, but are significantly less toxic than CdCl2. However, both sources of Cd lead to similar patterns of Cd bioaccumulation and distribution in L. minor fronds. Our results are in line with previous reports that the main mediators of Cd toxicity and bioaccumulation in aquatic plants are Cd2+ ions dissolved from Cd-based QDs.

Can earthworms biosynthesize highly luminescent quantum dots?

Band gap tunable cadmium selenide (CdSe) quantum dots (QDs) were synthesized within earthworms that emit in the middle of the visible spectrum. We demonstrated that this luminescence emission is a combination of the earthworm's protein and QD luminescence, such that the contribution of QDs in the luminescence was negligible. Eisenia fetida earthworms were used for QD biosynthesis and were exposed to different concentrations of CdCl2 and Na2 SeO3 in standard soil for an adequate exposure time. The size of the CdSe QDs based on the effective mass model was in agreement with the size measured from the transmission electron microscopy analysis, with an average diameter of 7 nm. Ultraviolet-visible and photoluminescence analyses confirmed the synthesis of CdSe QDs with unique absorption and luminescence at 430 nm and 605 nm, respectively.

A Nanobionic Light-Emitting Plant.

The engineering of living plants for visible light emission and sustainable illumination is compelling because plants possess independent energy generation and storage mechanisms and autonomous self-repair. Herein, we demonstrate a plant nanobionic approach that enables exceptional luminosity and lifetime utilizing four chemically interacting nanoparticles, including firefly luciferase conjugated silica (SNP-Luc), d-luciferin releasing poly(lactic-co-glycolic acid) (PLGA-LH2), coenzyme A functionalized chitosan (CS-CoA) and semiconductor nanocrystal phosphors for longer wavelength modulation. An in vitro kinetic model incorporating the release rates of the nanoparticles is developed to maximize the chemiluminescent lifetimes to exceed 21.5 h. In watercress (Nasturtium officinale) and other species, the nanoparticles circumvent limitations such as luciferin toxicity above 400 µM and colocalization of enzymatic reactions near high adenosine triphosphate (ATP) production. Pressurized bath infusion of nanoparticles (PBIN) is introduced to deliver a mixture of nanoparticles to the entire living plant, well described using a nanofluidic mathematical model. We rationally design nanoparticle size and charge to control localization within distinct tissues compartments with 10 nm nanoparticles localizing within the leaf mesophyll and stomata guard cells, and those larger than 100 nm segregated in the leaf mesophyll. The results are mature watercress plants that emit greater than 1.44 × 1012 photons/sec or 50% of 1 µW commercial luminescent diodes and modulate "off" and "on" states by chemical addition of dehydroluciferin and coenzyme A, respectively. We show that CdSe nanocrystals can shift the chemiluminescent emission to 760 nm enabling near-infrared (nIR) signaling. These results advance the viability of nanobionic plants as self-powered photonics, direct and indirect light sources.

Activation Thermodynamics and H/D Kinetic Isotope Effect of the Hox to HredH+ Transition in [FeFe] Hydrogenase.

Molecular complexes between CdSe nanocrystals and Clostridium acetobutylicum [FeFe] hydrogenase I (CaI) enabled light-driven control of electron transfer for spectroscopic detection of redox intermediates during catalytic proton reduction. Here we address the route of electron transfer from CdSe→CaI and activation thermodynamics of the initial step of proton reduction in CaI. The electron paramagnetic spectroscopy of illuminated CdSe:CaI showed how the CaI accessory FeS cluster chain (F-clusters) functions in electron transfer with CdSe. The Hox→HredH+ reduction step measured by Fourier-transform infrared spectroscopy showed an enthalpy of activation of 19 kJ mol-1 and a ∼2.5-fold kinetic isotope effect. Overall, these results support electron injection from CdSe into CaI involving F-clusters, and that the Hox→HredH+ step of catalytic proton reduction in CaI proceeds by a proton-dependent process.

Study on the Interaction of the CpG Alternating DNA with CdTe Quantum Dots.

A novel sensitive method for detection of DNA methylation was developed with thioglycollic acid (TGA)-capped CdTe quantum dots (QDs) as fluorescence probes. Recognition of methylated DNA sites would be useful strategy due to the important roles of methylation in disease occurrence and developmental processes. DNA methylation occurs most often at cytosine-guanine sites (CpG dinucleotides) of gene promoters. The QDs significantly interacted with hybridized unmethylated and methylated DNA. The interaction of CpG rich methylated and unmethylated DNA hybrid with quantum dots as an optical probe has been investigated by fluorescence spectroscopy and electrophoresis assay. The fluorescence intensity of QDs was highly dependent to unmethylated and methylated DNA. Specific site of CpG islands of Adenomatous polyposis coli (APC), a well-studied tumor suppressor gene, was used as the detection target. Under optimum conditions, upon the addition of unmethylated dsDNA, the fluorescence intensity increased in linear range from 1.0 × 10- 10 to 1.0 × 10- 6M with detection limit of 6.2 × 10- 11 M and on the other hand, the intensity of QDs showed no changes with addition of methylated dsDNA. We also demonstrated that the unmethylated and methylated DNA and QDs complexes showed different mobility in electrophoresis assay. This easy and reliable method could distinguish between methylated and unmethylated DNA sequences.