Simultaneous sensing of ferritin and apoferritin proteins using an iron-responsive dye and evaluation of physiological parameters associated with serum iron estimation

Proteomic and metabolic analysis of Moorella thermoacetica-g-C3N4 nanocomposite system for artificial photosynthesis

Artificial photosynthesis by microbe-semiconductor biohybrid systems has been demonstrated as a valuable strategy in providing sustainable energy and in carbon fixation. However, most of the developed biohybrid systems for light harvesting employ heavy metal materials, especially cadmium sulfide (CdS), which normally cause environmental pollution and restrict the widespread of the systems. Herein, we constructed an environmentally friendly biohybirid system based on a typical acetogenic bacteria, Moorella thermoacetica, coupling with a carbon-based semiconductor, graphitic carbon nitride (g-C3N4), to realize light-driven carbon fixation. The proposed biohybrid system displayed outstanding acetate productivity with a quantum yield of 2.66 ± 0.43 %. Non-targeted proteomic analysis indicated that the physiological activity of the bacteria was improved, coupling with the non-toxic material. We further proposed the mechanisms of energy generation, electron transfer and CO2 fixation of the irradiated biohybrid system by proteomic and metabolomic characterization. With the photoelectron generated in g-C3N4 under illumination, CO2 is finally converted to acetate via the Wood-Ljungdahl pathway (WLP). Other associated pathways were also proved to be activated, providing extra energy or substrates for acetate production. The study reveals that the future focus of the development of biohybrid systems for light harvesting can be on the metal-free biocompatible material, which can activate the expression of the key enzymes involved in the electron transfer and carbon metabolism under light irradiation.

Promoting photothermal antibacterial activity through an excited-state intramolecular proton transfer process

The construction of an efficient photothermal antibacterial platform is a promising strategy for the treatment of drug-resistant bacterial infections. Herein, through the introduction of excited-state intramolecular proton transfer to promote the photothermal effect, N-(2,4-dihydroxybenzylidene)-4-aminophenol (DOA)-polyvinyl alcohol (PVA) systems (DPVA) can reach 55 °C within 10 s under irradiation. They show superior antibacterial behavior against drug-resistant bacteria and a therapeutic effect on infected skin wounds with only 100 s of irradiation, much faster than those of reported photothermal materials (5-10 min). This work provides a convenient approach to fabricate broad-spectrum antibacterial wound dressings for treating bacteria-infected wounds, greatly contributing to the design and applications of photothermal antibacterial platforms.

A biocompatible hydrogel as a template for oxidative decomposition reactions: a chemodosimetric analysis and in vitro imaging of hypochlorite

The self-assembly properties of new biocompatible, thermoreversible fluorescent hydrogels, composed of amino acid residues have been reported. A unique gel-to-sol transition is triggered by chemodosimetric interaction in the presence of hypochlorite.

A simple strategy for the visual detection and discrimination of Hg2+ and CH3Hg+ species using fluorescent nanoaggregates

Fluorescent nanoaggregates (FNAs) based on phenanthroline-based amphiphiles show changes in solution color from colorless to yellow upon addition of both Hg²⁺ (LOD ∼4 ppb) and CH₃Hg⁺ (LOD ∼18 ppb). However, the extent of fluorescence quenching is more prominent with Hg²⁺ (∼12 fold) than with CH₃Hg⁺ (∼4 fold). Also, unlike Hg²⁺, the interaction of CH₃Hg⁺ needs more time, ∼10 min at room temperature. Experimental evidence indicates that both mercury species coordinate with the phenanthroline unit and facilitate the charge transfer interaction while destabilizing the nanoassembly. The lower charge density on CH₃Hg⁺ along with its large size compared to Hg²⁺ may be the reason for such observations. Interestingly, FNAs show a selective response towards CH₃Hg⁺ when pre-treated with EDTA. Further, analysis of heavy metal pollutants in drinking water and biological samples was performed. High recovery values ranging from 96% to 103.0% were estimated along with relatively small standard deviations (<3%). Low-cost, reusable test strips were designed for rapid, on-site detection of mercury species. Further, the in situ formed metal complexes are allowed to interact with thiol-containing amino acids. As expected, CH₃Hg⁺, being less thiophillic, endures less interaction with cysteine. Mechanistic investigations indicate that thiolated amino acids can bind with the metal ion center and form a tertiary complex (cooperative interaction).

Metal-Ion-Responsive Chromogenic Probe for Rapid, On-Location Detection of Foodborne Bacterial Pathogens in Contaminated Food Items

An amphiphilic chromogenic probe based on an oxidized di(indolyl)arylmethane backbone has been utilized for visual detection of both Cu²⁺ (detection limit = 8.5 ppb) and Hg²⁺ (detection limit = 10.2 ppb) ions via mutually independent sensing pathways. The Cu²⁺ ion binds to the carboxylate ends (donor site) and induces a color change from orange to yellow in the aqueous medium, while coordinating Hg²⁺ at the bisindolyl moiety (acceptor site) can result in the formation of a red-colored solution. Interestingly, by selecting the proper excitation channel, we can specifically excite either the monomer species or nanoaggregates. The addition of Hg²⁺ enhances the monomer fluorescence, while Cu²⁺ induces quenching. However, in both cases, metal-ion coordination triggers dissociation of a preformed self-assembled structure. Further, the in-situ-formed Cu(II) complex was utilized for rapid, on-location detection of food-borne pathogens, such as Escherichia coli (E. coli) in contaminated food items and water (detection limit = 52 CFU·mL^-1). E. coli induces reduction of Cu²⁺ to Cu⁺ and transforms the yellow-colored solution into an orange-colored solution. Finally, low-cost, reusable paper strips were designed as an eco-friendly, sustainable strategy to detect bacterial pathogens.

Highly sensitive naphthalimide based Schiff base for the fluorimetric detection of Fe3

A simple 1,8-naphthalimide based Schiff base probe (E)-6-((4-(diethylamino)-2-hydroxybenzylidene)amino)-2-(2-morpholinoethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (NDSM) has been designed and synthesized for the specific detection of Fe3+ based on a fluorimetric mode. The absorbance of NDSM at 360 nm increased significantly in acetonitrile : water (7 : 3, v/v) medium only in the presence of Fe3+ ions with a visible colour change from yellow to golden yellow. Likewise, fluorescence emission intensity at 531 nm was almost wholly quenched in the presence of Fe3+. However, other competitive ions influenced insignificantly or did not affect the optical properties of NDSM. Lysosome targetability was expected from NDSM due to the installation of a basic morpholine unit. The LOD was found to be 0.8 μM with a response time of seconds. The fluorescence reversibility of NDSM + Fe3+ was established with complexing agent EDTA. Fe3+ influences the optical properties of NDSM by complexing with it, which blocks C[double bond, length as m-dash]N isomerization in addition to the ICT mechanism. The real-time application of Fe3+ was demonstrated in test paper-based detection, by the construction of a molecular logic gate, quantification of Fe3+ in water samples and fluorescence imaging of Fe3+.

Dual-probe (colorimetric and fluorometric) detection of ferritin using antibody-modified gold@carbon dot nanoconjugates

A dual-mode assay is described for immunological determination of the anemia biomarker ferritin. It is based on the use of a gold@carbon dot (Au@CD) nanoconjugate as a colorimetric and fluorescent probe. Au@CD is hydrophilic, easily surface modified and stable in aqueous solution. The Au@CD have a red color with blue-green fluorescence and were modified with antibody against ferritin. This allows bi-modal detection of ferritin. Assays can be performed in phosphate buffer and were also analyzed in (Bovine Serum Albumin) BSA and (Fetal Bovine Serum) FBS. Detection is based on antigen-antibody interaction underlying the classical sandwich model. Response to ferritin can be detected by spectrophotometry (at 570 nm) or fluorescence (at excitation/emission maxima of 354/454 nm). Under optimal conditions, the assay has a linear response in the 1 to 120 ngmL^-1 ferritin concentration range and detection limits of 20 ng (colorimetrically) and 64 ng (fluorometrically). Graphical abstract Schematic representation of the function of the designed nanoprobe. The Au@CD nanoconjugates are functionalized with ferritin antibody in the initial step which specifically interacts with ferritin molecules leading to aggregation and subsequent changes in the optical and fluorescence signals.

An easy-to-synthesize multi-photoresponse smart sensor for rapidly detecting Zn2+ and quantifying Fe3+ based on the enol/keto binding mode

A readily available salicylaldazine-modified fluorene Schiff base (EASA-F) exhibits fast fluorescent OFF–ON response to Zn²⁺ and OFF–ON–OFF behavior to Fe³⁺ synchronously accompanied the diverse absorption-ratiometric and colorimetric changes.