Multifunctional Self-Healing Carbon Dot-Gelatin Bioadhesive: Improved Tissue Adhesion with Simultaneous Drug Delivery, Optical Tracking, and Photoactivated Sterilization.

Bioadhesives with all-inclusive properties for simultaneous strong and robust adhesion, cohesion, tracking, drug delivery, self-sterilization, and nontoxicity are still farfetched. Herein, a carbon dot (CD) is made to infuse each of the above-desired aspects with gelatin, an inexpensive edible protein. The CD derived through controlled hydrothermal pyrolysis of dopamine and terephthaldehyde retained -NH2, -OH, -COOH, and, most importantly, -CHO functionality on the CD surface for efficient skin adhesion and cross-linking. Facile fabrication of CD-gelatin bioadhesive through covalent conjugation of -CHO of the CD with -NH2 of gelatin through Schiff base formation was accomplished. This imparts remarkable self-healing attributes as well as excellent adhesion and cohesion evident from physicomechanical analysis in a porcine skin model. Improved porosity of the bioadhesive allows loading hemin as a model drug whose disembarkment is tracked with intrinsic CD photoluminescence. In a significant achievement, antibiotic-free self-sterilization of bioadhesive is demonstrated through visible light (white LED, 23 W)-irradiated photosensitization of the CD to produce reactive oxygen species for annihilation of both Gram-positive and Gram-negative bacteria with exceptional efficacy (99.9%). Thus, a comprehensive CD-gelatin bioadhesive for superficial and localized wound management is reported as a promising step for the transformation of the bioadhesive domain through controlled nanotization for futuristic clinical translations.

Correction: A biomass-derived dual crosslinked DNA-nanoparticle hydrogel for visible light-induced photodynamic bacterial inactivation.

Correction for 'A biomass-derived dual crosslinked DNA-nanoparticle hydrogel for visible light-induced photodynamic bacterial inactivation' by Gourab Das et al., Soft Matter, 2023, https://doi.org/10.1039/D3SM01400B.

A biomass-derived dual crosslinked DNA-nanoparticle hydrogel for visible light-induced photodynamic bacterial inactivation.

Sustainability in developing novel nanomaterials (NPs) from biomass sources is a challenging proposition mainly due to the difficulty of infusing or retaining desired chemical functionalities in the biomass substrate. In this study, we demonstrate the synthesis of DNA-nanoparticles (DNA-NP) from onion genomic DNA as a plant biomass source through controlled hydrothermal pyrolysis to retain functional groups in the NPs for predictable downstream chemical transformations. A dual crosslinking scheme was introduced that involves the DNA-NP to form a hydrogel. Chemical crosslinking was achieved through the formation of a Schiff base between the -CHO groups of glutaraldehyde and the amine functionality present on the DNA-NP surface as well as in the nucleobases of the dangling DNA strands of DNA-NP. Simultaneous physical entanglement was attained through hybridization-mediated self-assembly of the dangling DNA strands of the DNA-NP with untransformed onion genomic DNA. As a corollary of the dual crosslinking, the resulting hydrogel not only displayed remarkable mechanical strength but also showed self-healing properties. The ability of the DNA-NP to generate reactive oxygen species (ROS) with visible light irradiation is translated to the hydrogel, making the system potent for biofilm destruction. The high loading efficiency of the model drug ampicillin sodium (Amp) in the hydrogel was achieved which was released in four days. This hints towards the application of the hydrogel through combination antibiotic-antibacterial photodynamic treatment (APDT) as demonstrated here with both Gram-positive and Gram-negative bacteria.

Elucidating the relationship between red fluorescence and structural dynamics of carbon dots dispersed in different solvents.

The mechanism of intrinsic fluorescence of carbon dots (CDs), the latest nanomaterial from the carbon family, was supposedly deciphered through multiple theories. However, the much sought-after persistent red emission of CDs as a foreseeable consequence of experiments remains elusive prompting the question of whether tuning of the red emission of CDs is a predictable outcome or a serendipitous coincidence. Herein, we tried to decode the same by exploring Alizarin Red S (ARS)-based red emitting CDs in different solvents with wisely chosen analytical tools. The findings are aptly supported by molecular dynamics studies through an experimental intuition-driven model-building approach. Parallel interception of the CDs with powder X-ray diffraction (pXRD) and photophysical spectroscopic studies revealed an important relationship between the solvent and CDs. Tautomerism, a well-known phenomenon with chemical entities, was found to be operative for CDs that greatly influence the Stokes shift and ultimately the fluorescence outcome. Most importantly, pXRD studies established the turbostratism of the CDs where the well-ordered graphitic structure of CDs gets disrupted with solvent molecules. The extent of such disruption is a function of solvent and CD composition that plays a formidable role in obtaining red fluorescence. Thus, for the first time, we demonstrate that the red emission of CDs is related to its structural integrity and if taken care of could be sustained, a tremendously desirable outcome for relevant applications.

Machine Learning-Mediated Ultrasensitive Detection of Citrinin and Associated Mycotoxins in Real Food Samples Discerned from a Photoluminescent Carbon Dot Barcode Array.

Economically viable remote sensing of foodborne contaminants using minimalistic chemical reagents and simultaneous automation calls for a concrete integration of a chemical detection strategy with artificial intelligence. In a first of its kind, we report the ultrasensitive detection of citrinin and associated mycotoxins like aflatoxin B1 and ochratoxin A using an Alizarin Red S (ARS) and cystamine-derived carbon dot (CD) that aptly amalgamate with machine learning algorithms for automation. The photoluminescence response of the CD as a function of various solvents and pH is used to generate array channels that are further modulated in the presence of the mycotoxins whose digital images were acquired to determine pixelation, essentially creating a barcode. The barcode was fed to machine learning algorithms that actualize and intertwine convoluted databases, demonstrating Extreme Gradient Boosting (XGBoost) as the optimized model out of eight algorithms tested. Spiked samples of wheat, rice, gram, maize, coffee, and milk were used to evaluate the testing model where an exemplary accuracy of 100% even at 10 pmol of mycotoxin concentration was achieved. Most importantly, the coexistence of mycotoxins could also be detected through the CD array and XGBoost synergy hinting toward a broader scope of the developed methodology for smart detection of foodborne contaminants.

Carbon dot-based superhydrophobic modification of a covalent organic framework for oil-in-water emulsion separation.

A super hydrophobic composite is developed for the first time through the non-covalent self-assembly of a hydrophilic covalent organic framework (COF) and amphoteric CDs to achieve highly selective separation of dispersed micro droplets of oil from an oil/water mixture.

Simultaneous Sustained Drug Delivery, Tracking, and On-Demand Photoactivation of DNA-Hydrogel Formulated from a Biomass-Derived DNA Nanoparticle.

Conversion of biomass into nanoparticles for meaningful biomedical applications is a formidable proposition with excellent prospects but fewer patrons. A lack of general methodology for upscaled production and limited versatility of those nanoparticles are the main drawbacks. Herein, we report the creation of a DNA nanoparticle (DNA Dots) from onion genomic DNA (gDNA), a plant biomass source, through controlled hydrothermal pyrolysis in water without any chemicals. The DNA Dots are further formulated into a stimuli-responsive hydrogel through hybridization-mediated self-assembly with untransformed precursor gDNA. The versatility of the DNA Dots is recognized through its crosslinking ability with gDNA through its dangling DNA strands on the surface resulting from incomplete carbonization during annealing without the need for any external organic, inorganic, or polymeric crosslinkers. The gDNA-DNA Dots hybrid hydrogel is shown to be an excellent drug delivery vehicle for sustained release trackable through the inherent fluorescence of the DNA Dots. Interestingly, the DNA Dots are photoexcited with normal visible light to generate on-demand reactive oxygen species, making them exciting candidates for combination therapeutics. Most importantly, the ease with which the hydrogel is internalized in fibroblast cells with minimal cytotoxicity should encourage the nanotization of biomass as a tool for interesting sustainable biomedical applications.

Chemically induced crosslinked enhanced emission of carbon polymer dots discerning healthy and cancer cells through pH-dependent tunable photoluminescence.

Chemically induced crosslinked enhanced emission (CEE) of urea and citric acid-derived carbon polymer dot (CPD) nanoparticles is established here with a rare zero linker approach, i.e. without the use of any separate crosslinkers. Such chemical CEE like any chemical reaction was achieved through amide bond formation using carbodiimide chemistry, pointing towards the feasibility of developing a general methodology for their formation through engineering the nanoparticle surface functionality. Exhaustive characterization was done to pinpoint the structure, morphology, and photophysics of the CPDs and concurrently eliminate the possibility of the involvement and interference by molecular fluorophores for the unique optical tuning of the CPDs. The structure-photophysics relation was further restated through theoretical studies involving density functional theory (DFT) that correlated significantly well with the experimental findings. Most interestingly, the CPDs revealed pH responsiveness due to the formation or hydrolysis of amide bonds with acid or base, respectively, which was manifested through a spectacular change in fluorescence emission visible to the naked eye through UV illumination. This distinct pH-dependent photoluminescence properties of CPDs opens up an enormous opportunity for interesting applications, including discriminating normal and cancerous cells, which we demonstrate herein as a proof of concept through in vitro imaging.

Biomass derived self-assembled DNA-dot hydrogels for enhanced bacterial annihilation.

Nanotization of biomass for interesting biomedical applications is still in the nascent stage with no visible market available products. While products derived from biomass DNA and protein have unquestionable biocompatibility, induction of desired properties needs careful manipulation of the biomolecules. Herein, for the first time, we report the transformation of onion derived biomass DNA into DNA-dots through its partial hydrothermal pyrolysis to induce improved mechanical and photophysical properties. The DNA-dots were further used as crosslinkers to create a hydrogel through hybridization-mediated self-assembly with untransformed genomic DNA. The DNA dot-DNA hydrogel sustainably delivers the ciprofloxacin antibiotic as well as produces on-demand reactive oxygen species (ROS) with visible light irradiation. This prompted us to explore the hydrogel as a topical formulation for combination antibiotic Antibacterial-Photodynamic Therapy (APDT) applications. Remarkable annihilation of E. coli and S. aureus, and most importantly two drug-resistant strains of E. coli, shows the success of our sustainable approach.

Mechanistic insight into the role of mevalonate kinase by a natural fatty acid-mediated killing of Leishmania donovani.

We evaluated the anti-leishmanial efficacy of different saturated medium-chain fatty acids (FAs, C8-C18) where FA containing C8 chain, caprylic acid (CA), was found to be most potent against Leishmania donovani, the causative agent for visceral leishmaniasis (VL). Different analogs of CA with C8 linear chain, but not higher, along with a carboxyl/ester group showed a similar anti-leishmanial effect. Ergosterol depletion was the major cause of CA-mediated cell death. Molecular docking and molecular dynamic simulation studies indicated the enzyme mevalonate kinase (MevK) of the ergosterol biosynthesis pathway as a possible target of CA. Enzyme assays with purified recombinant MevK and CA/CA analogs confirmed the target with a competitive inhibition pattern. Using biochemical and biophysical studies; strong binding interaction between MevK and CA/CA analogs was established. Further, using parasites with overexpressed MevK and proteomics studies of CA-treated parasites the direct role of MevK as the target was validated. We established the mechanism of the antileishmanial effect of CA, a natural product, against VL where toxicity and drug resistance with current chemotherapeutics demand an alternative. This is the first report on the identification of an enzymatic target with kinetic parameters and mechanistic insights against any organism for a natural medium-chain FA.

Visible light-induced charge injection and migration in self-assembled carbon dot-DNA-carbon dot nano-dumbbell obtained through controlled stoichiometric conjugation.

The potential of carbon dots (CDs) for photonic conversion to charged states, together with the ability of DNA to transport such charge for extensive charge separation, offers an opportunity to control directionality of migration for photo-induced radical cations in CD-DNA based nano-assemblies. This is achieved through engineering the reaction valency of CDs whereby one CD is covalently conjugated with one ssDNA strand. Subsequently, a CD-DNA-CD nano-dumbbell architecture was created through hybridization mediated self-assembly. The time and intensity-dependent transduction of visible light photonic energy to chemical potential in DNA was achieved through irradiation of 1,4-diaminoathraquinone and glyoxal derived CD with 100 W tungsten source and natural sunlight. Following charge injection by CD, the radical cation migration in DNA was perceived through trapping of the hole in repeated GG steps in the DNA. Overall, a breakthrough in visible-light-induced charge transfer by CD into DNA was achieved, potentially applicable to optobioelectronics.

Covalent Conjugation of Carbon Dots with Plasmid and DNA Condensation Thereafter: Realistic Insights into the Condensate Morphology, Energetics, and Photophysics.

The use of carbon quantum dots (CDs) as trackable nanocarriers for plasmid and gene as hybrid DNA condensates has gained momentum, as evident from the significant recent research efforts. However, the in-depth morphology of the condensates, the energetics of the condensation process, and the photophysical aspects of the CD are not well understood and often disregarded. Herein, for the first time, we covalently attached linearized pUC19 with citric acid and cysteamine-derived CD through the reaction of the surface amine groups of CDs with the 5'-phospho-methyl imidazolide derivative of the plasmid to obtain a 1:1 CD-pUC19 covalent conjugate. The CD-pUC19 conjugates were further transformed into DNA condensates with spermine that displayed a toroidal morphology with a diameter of ∼200 nm involving ∼2-5 CD-pUC19 conjugates in a single condensate. While the interaction of pristine CD to spermine was exothermic, the binding of the CD-pUC19 conjugate with spermine was endothermic and primarily entropy-driven. The condensed plasmid displayed severe conformational stress and deviation from the B-form due to the compact packing of the DNA but better transfection ability than the pristine CD. The CDs in the condensates tend to come close to each other at the core that results in their shielding from excitation. However, this does not prevent them from emanating reactive oxygen species on visible light exposure that compromises the decondensation process and cell viability at higher exposure times, calling for utmost caution in establishing them as nonviral transfecting agents universally.

7,8-dihydroxyflavone-functionalized gold nanoparticles target the arginase enzyme of Leishmania donovani.

Aim: To analyze the efficacy and possible mechanism of action of 7,8-dihydroxyflavone (DHF) and DHF synthesized gold nanoparticles (GNPs) against the parasite Leishmania donovani. Methods: GNPs were synthesized using DHF and characterized by dynamic light scattering, ζ potential, Fourier transform infrared spectroscopy, transmission electron microscopy and x-ray diffraction. The efficacy of DHF and DHF-GNP were tested against sensitive and drug-resistant parasites. GNP uptake was measured on macrophages by atomic absorption spectroscopy. Results: DHF and DHF-GNP (∼35 nm) were equally effective against sensitive and drug-resistant strains and inhibited the arginase activity of parasites. Increased IFN-γ and reduced IL-12 cytokine response showed a Th1/Th2-mediated cell death in macrophages. Conclusion: The low cytotoxicity and high biological activity of DHF-GNP may be useful for chemotherapy of leishmaniasis.

Synthesis of 2-Chloro-3-amino indenone derivatives and their evaluation as inhibitors of DNA dealkylation repair.

DNA alkylation damage, emanating from the exposure to environmental alkylating agents or produced by certain endogenous metabolic processes, affects cell viability and genomic stability. Fe(II)/2-oxoglutarate-dependent dioxygenase enzymes, such as Escherichia coli AlkB, are involved in protecting DNA from alkylation damage. Inspired by the natural product indenone derivatives reported to inhibit this class of enzymes, and a set of 2-chloro-3-amino indenone derivatives was synthesized and screened for their inhibitory properties against AlkB. The synthesis of 2-chloro-3-amino indenone derivatives was achieved from 2,3-dichloro indenones through addition-elimination method using alkyl/aryl amines under catalyst-free conditions. Using an in vitro reconstituted DNA repair assay, we have identified a 2-chloro-3-amino indenone compound 3o to be an inhibitor of AlkB. We have determined the binding affinity, mode of interaction, and kinetic parameters of inhibition of 3o and tested its ability to sensitize cells to methyl methanesulfonate that mainly produce DNA alkylation damage. This study established the potential of indenone-derived compounds as inhibitors of Fe(II)/2-oxoglutarate-dependent dioxygenase AlkB.

The HIV - 1 protease inhibitor Amprenavir targets Leishmania donovani topoisomerase I and induces oxidative stress-mediated programmed cell death.

The global prevalence of HIV is a major challenge for the control of visceral leishmaniasis. Although the effectiveness and usefulness of amprenavir (APV) are well studied in anti-retroviral regimens, very little is known on HIV/VL-co-infected patients. In the present study, we report for the first time the protective efficacy of APV against visceral leishmaniasis by inhibition of DNA Topoisomerase I (LdTOP1LS) and APV-induced downstream pathway in programmed cell death (PCD). During the early phase of activation, reactive oxygen species (ROS) is increased inside the cells, which causes subsequent elevation of lipid peroxidation. Endogenous ROS formation and lipid peroxidation cause eventual depolarization of mitochondrial membrane potential (ΔΨm). Furthermore, the release of cytochrome c and activation of CED3/CPP32 group of proteases lead to the formation of oxidative DNA lesions followed by DNA fragmentation. The promising in vitro and ex vivo results promoted to substantiate further by in vivo animal experiment, which showed a significant reduction of splenic and hepatic parasites burden compared to infected controls. Interestingly, APV selectively targets LdTOPILS and does not inhibit the catalytic activity of human topoisomerase I (hTopI). Moreover, based on the cytotoxicity test APV is not toxic for host macrophage cells, which is correlated with non-responsiveness of inhibition of catalytic activity of hTopI. Taken together, this study provides the opportunity for discovering and evaluating newer potential molecular therapeutic targets for drug designing. The present study might be exploited in future as important therapeutics, which will be useful for treatment of VL as well as HIV-VL co-infection.

Carbon dot cross-linked polyvinylpyrrolidone hybrid hydrogel for simultaneous dye adsorption, photodegradation and bacterial elimination from waste water.

The creation of a polymeric hydrogel from polyvinylpyrrolidone (PVP) cross-linked by Carbon Quantum Dots (CD) for the adsorption and photocatalytic degradation of both cationic and anionic dyes. PVP, an important biocompatible constituent and often surplus in cosmetic industry, was carboxylated through NaOH refluxing and covalently conjugated to surface amine functionality of CD derived from lemon juice and Cysteamine. The hybrid hydrogel was obtained from PVP-CD covalent conjugate by careful manipulation of pH and found to possess better rheological properties than only carboxylate-PVP. The monolayer physisorption of the dyes on the hydrogel was affected by hydrogen bonding, dispersion or inductive effect, and π-π interaction with the polymer backbone as well as the CD that followed pseudo-second-order kinetics. Degradation of the adsorbed dyes was instated by the unique Reactive Oxygen Species (ROS) generating ability of the CD embedded in the hydrogel matrix upon exposure to sunlight, the mechanism of which is also unveiled. The same CD-induced ROS was found to effectively annihilate both gram-positive and gram-negative bacteria in real polluted water in less than 10 min of photoexcitation of the hydrogel. The hydrogel was restored by mild acid wash that is able to perform dye adsorption and photo-degradation upto four cycles.

One-Pot Synthesis of Orange-Red Fluorescent Dimeric 2H-Pyrrolo[2,3-c]isoquinoline-2,5(3H)-diones from Benzamides and Maleimides via Ru(II)-Catalyzed Sequential C-C/C-N/C-C Bond Formation.

We report here a direct and efficient strategy for the synthesis of highly conjugated dimeric pyrrolo-fused isoquinoline derivatives from readily available benzamides and maleimides. This reaction overall proceeds by following a domino approach: C-C bond formation via challenging primary amide-directed Ru(II)-catalyzed ortho alkenylation followed by annulation and C-C bond formation through Ru(II)-catalyzed dehydrogenative dimerization. The resulting products showed substituent-dependent tunable photoluminescence in the orange-red region with reasonably large Stokes shifts and interesting redox properties.

Ultrasensitive visual detection of mycotoxin citrinin with yellow-light emitting carbon dot and Congo red.

Ultrasensitive visual detection of mycotoxin citrinin is reported here using a novel yellow-light emitting Carbon dot (CD) and Congo red dye. Detection strategy is based on higher binding affinity of citrinin with diammonium citrate, and urea derived CD over Congo red in presence of Mg2+. Congo red statically quenched the yellow fluorescence of CD, resulting in emission in red region, which was restored in presence of citrinin. Visual limit of detection (LOD) of 10 pmol and spectroscopic LOD of 6.6 pmol/mL was achieved within 5 min of incubation with citrinin. The assembly was found to respond well for citrinin detection in the presence of Aflatoxin b1 (AFL b1) and Ochratoxin A (OTA), that frequently co-exist with citrinin in real food samples. The method exhibits immense potential to sense citrinin in sub-nanogram range by visual inspection in an inexpensive yet robust on-site detection platform in relevant food packaging and agricultural industry.

Hybrid DNA-Carbon Dot-Poly(vinylpyrrolidone) Hydrogel with Self-Healing and Shape Memory Properties for Simultaneous Trackable Drug Delivery and Visible-Light-Induced Antimicrobial Photodynamic Inactivation.

A two-step methodology for simultaneous conjugation of DNA and poly(vinylpyrrolidone) (PVP) polymer to a single carbon quantum dot (CD) is demonstrated for the first time to fabricate a pH-responsive DNA-CD-PVP hybrid hydrogel. Cross-linking in the hydrogel was achieved using CD as the common nucleus through the formation of DNA I-motif conformation at neutral to acidic pH and noncovalent interaction of PVP that infuse self-healing and shape memory properties in the hydrogel. The hydrogel is capable of loading and sustained delivery of drugs for more than 2 weeks as demonstrated using a model drug, Hemin. The quenching of fluorescence of CD by Hemin was trackable even through simple visual monitoring, which showed that Hemin can diffuse from the loaded part to the unloaded part of the hydrogel during the self-healing process. Most significantly, the chosen CD generates reactive oxygen species (ROS) upon visible light irradiation, armoring the hydrogel with worthy antimicrobial activity. Biocompatibility of the DNA-CD-PVP hydrogel was established on human fibroblast cells, indicating their potential use in biomedical area pertaining to wound healing.

Synthesis, characterization, and mechanistic studies of a gold nanoparticle-amphotericin B covalent conjugate with enhanced antileishmanial efficacy and reduced cytotoxicity.

BACKGROUND: Amphotericin B (AmB) as a liposomal formulation of AmBisome is the first line of treatment for the disease, visceral leishmaniasis, caused by the parasite Leishmania donovani. However, nephrotoxicity is very common due to poor water solubility and aggregation of AmB. This study aimed to develop a water-soluble covalent conjugate of gold nanoparticle (GNP) with AmB for improved antileishmanial efficacy and reduced cytotoxicity. METHODS: Citrate-reduced GNPs (~39 nm) were functionalized with lipoic acid (LA), and the product GNP-LA (GL ~46 nm) was covalently conjugated with AmB using carboxyl-to-amine coupling chemistry to produce GNP-LA-AmB (GL-AmB ~48 nm). The nanoparticles were characterized by dynamic light scattering, transmission electron microscopy (TEM), and spectroscopic (ultraviolet-visible and infrared) methods. Experiments on AmB uptake of macrophages, ergosterol depletion of drug-treated parasites, cytokine ELISA, fluorescence anisotropy, flow cytometry, and gene expression studies established efficacy of GL-AmB over standard AmB. RESULTS: Infrared spectroscopy confirmed the presence of a covalent amide bond in the conjugate. TEM images showed uniform size with smooth surfaces of GL-AmB nanoparticles. Efficiency of AmB conjugation was ~78%. Incubation in serum for 72 h showed <7% AmB release, indicating high stability of conjugate GL-AmB. GL-AmB with AmB equivalents showed ~5-fold enhanced antileishmanial activity compared with AmB against parasite-infected macrophages ex vivo. Macrophages treated with GL-AmB showed increased immunostimulatory Th1 (IL-12 and interferon-γ) response compared with standard AmB. In parallel, AmB uptake was ~5.5 and ~3.7-fold higher for GL-AmB-treated (P<0.001) macrophages within 1 and 2 h of treatment, respectively. The ergosterol content in GL-AmB-treated parasites was ~2-fold reduced compared with AmB-treated parasites. Moreover, GL-AmB was significantly less cytotoxic and hemolytic than AmB (P<0.01). CONCLUSION: GNP-based delivery of AmB can be a better, cheaper, and safer alternative than available AmB formulations.