Carbonized Polymer Dot-Tannic Acid Nanoglue: Tissue Reinforcement with Concurrent Fluorescent Tracking, Insulin Delivery, and Reactive Oxygen Species Regulation for Normal and Diabetic Wound Healing.

Nanotizing biosealant components offer a multitude of chemical functionalities for superior adhesion-cohesion, delivering unique properties for comprehensive wound healing that are otherwise impossible to achieve using commercial variants. For the first time, a two-step controlled hydrothermal pyrolysis is reported to nanotize dopamine, phloroglucinol, and glutaraldehyde into carbon dot (CD) to be subsequently converted into carbonized polymer dot (CPD) with gelatin as a co-substrate. Chemical crosslinking of CD with gelatin through Schiff base formation before the second pyrolysis step ensures a complex yet porous polymeric network. The retention of chemical functionalities indigenous to CD substrates and gelatin along with the preservation of CD photoluminescence in CPD for optical tracking is achieved. A unique nanoformulation is created with the CPD through tannic acid (TA) grafting evolving CPD-TA nanoglue demonstrating ≈1.32 MPa strength in lap shear tests conducted on porcine skin, surpassing traditional bioadhesives. CPD-TA nanoglue uploaded insulin as chosen cargo disbursal at the wound site for healing normal and in vitro diabetic wound models using HEKa cells with extraordinary biocompatibility. Most importantly, CPD-TA can generate reactive oxygen species (ROS) and scavenge simultaneously under ambient conditions (23 W white LED or dark) for on-demand sterilization or aiding wound recovery through ROS scavenging.

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.

Heterobimetallic (FeII/PtII)-Based Supramolecular Coordination Complexes Using 1,1'-Ferrocene Dicarboxylate: Self-Assembly and Interaction with Carbon Dots.

The synthesis and characterization of a new pyrazine-based ditopic organoplatinum(II) complex having a bite angle of 180° is reported. The facile and efficient syntheses are described of three discrete neutral Fe(II)/Pt(II) heterobimetallic SCCs with Pt(II) acceptor clips of different binding angles, 0, 120, and 180°. These new SCCs were characterized by multinuclear NMR and mass spectrometry. Electrochemical response of these ferrocene containing self-assembled ensembles was studied using cyclic voltammetry. The diplatinum acceptor organometallic clips significantly quench the fluorescence of highly emitting carbon quantum dots (CD), while the self-assembled macrocycles tend to nullify the quenching effect of the organometallic clips. Interestingly, the inefficient quenching of CD fluorescence by these SCCs was found to be directly related to the angular disposition of the binding sites in the Pt(II) based organometallic clips.

Creation of Linear Carbon Dot Array with Improved Optical Properties through Controlled Covalent Conjugation with DNA.

Controlled conjugation of fluorescent carbon dots (CDs) with DNA and subsequent fabrication of the CDs into an array through hybridization mediated self-assembly in the solution phase is reported. Covalent conjugation of CD with DNA and the subsequent array formation change the mobility of the CD-DNA array in gel electrophoresis and HPLC significantly. Interspatial distance in the CD-DNA array is tuned by the DNA sequence length and maintained at ∼8 ± 0.3 nm as revealed by electron microscopy studies. An increase in fluorescence lifetime by ∼2 ns was observed for the CD-DNA array compared to a solitary CD, vis-á-vis better imaging prospects of HEK293 cells by the former. Thus, the array displays improved fluorescence and unhindered cell penetration.

Indenone derivatives as inhibitor of human DNA dealkylation repair enzyme AlkBH3.

The mammalian AlkB homologue-3 (AlkBH3) is a member of the dioxygenase family of enzymes that in humans is involved in DNA dealkylation repair. Because of its role in promoting tumor cell proliferation and metastasis of cancer, extensive efforts are being directed in developing selective inhibitors for AlkBH3. Here we report synthesis, screening and evaluation of panel of arylated indenone derivatives as new class of inhibitors of AlkBH3 DNA repair activity. An efficient synthesis of 2,3-diaryl indenones from 2,3-dibromo indenones was achieved via Suzuki-Miyaura cross-coupling. Using a robust quantitative assay, we have obtained an AlkBH3 inhibitor that display specific binding and competitive mode of inhibition against DNA substrate. Finally, we established that this compound could prevent the proliferation of lung cancer cell line and enhance sensitivity to DNA damaging alkylating agent.

DNA mediated assembly of quantum dot-protoporphyrin IX FRET probes and the effect of FRET efficiency on ROS generation.

Photodynamic therapy (PDT) involves generation of reactive oxygen species (ROS) by the irradiation of a photosensitizer. Controlled and targeted release of ROS by a photosensitizer is crucial in PDT. For achieving controlled generation of ROS, a ZnSe/ZnS quantum dot (QD) donor and protoporphyrin IX (Pp IX) acceptor based fluorescence resonance energy transfer (FRET) probe is reported here. The QDs and Pp IX are assembled either by direct conjugation or through DNA hybridization. Complementary DNA strands are individually conjugated to the QDs and Pp IX by amide coupling. Due to the overlap of the emission spectrum of QDs and the absorption spectrum of Pp IX, efficient transfer of energy from QDs to Pp IX was observed in both the cases. The FRET efficiency was quantitatively evaluated by steady-state and time-resolved spectroscopy and compared between the QD-Pp IX direct conjugate and QD-DNA-Pp IX assembly at various donor to acceptor ratios. Since a single QD can harbor a multiple number of Pp IX-DNA counterparts through DNA hybridization, the FRET efficiency was found to increase with the increase in the number of Pp IX acceptors. ROS generation from Pp IX was studied for the FRET pairs and was found to be affected by the irradiation time of the QD donor.

Binding and interaction of di- and tri-substituted organometallic triptycene palladium complexes with DNA.

Two triptycene-based ligands with pendant bromophenyl units have been prepared. These triptycene derivatives have been used as synthons for the synthesis of di and tri nuclear palladium complexes. The organic molecules and their corresponding organometallic complexes have been fully characterized using nuclear magnetic resonance (NMR), infrared (IR) spectroscopy and mass spectrometry. The mode of binding and effect of the complexes on pUC19 plasmid, calf thymus DNA and oligomer duplex DNA have been investigated by a host of analytical methods. The complexes brought about unwinding of supercoiled plasmid and the unwinding angle was found to be related to the binding affinity of the complexes with DNA, where both these parameters were guided by the structure of the complexes. Concentration-dependent inhibition of endonuclease activity of SspI and BamHI by the complexes indicates preference for G/C sequence for binding to DNA. However, neither the complexes did not introduce any cleavage at abasic site in oligomer duplex DNA, nor they created linear form of the plasmid upon co-incubation with the DNA samples. The interactions of the complexes with DNA were found to be strongly guided by the structure of the complexes, where intercalation as well as groove binding was observed, without inflicting any damage to the DNA. The mode of interaction of the complexes with DNA was further confirmed by isothermal calorimetry.

Synthesis, characterization and DNA interaction studies of new triptycene derivatives.

A facile and efficient synthesis of a new series of triptycene-based tripods is being reported. Using 2,6,14- or 2,7,14-triaminotriptycenes as synthons, the corresponding triazidotriptycenes were prepared in high yield. Additionally, we report the transformation of 2,6,14- or 2,7,14-triaminotriptycenes to the corresponding ethynyl-substituted triptycenes via their tribromo derivatives. Subsequently, derivatization of ethynyl-substituted triptycenes was studied to yield the respective propiolic acid and ethynylphosphine derivatives. Characterization of the newly functionalized triptycene derivatives and their regioisomers were carried out using FTIR and multinuclear NMR spectroscopy, mass spectrometry, and elemental analyses techniques. The study of the interaction of these trisubstituted triptycenes with various forms of DNA revealed interesting dependency on the functional groups of the triptycene core to initiate damage or conformational changes in DNA.

PEG-mediated one-pot multicomponent reactions for the efficient synthesis of functionalized dihydropyridines and their functional group dependent DNA cleavage activity.

Polyethylene glycol (PEG) has been found to be an inexpensive, non-toxic and useful medium for the one pot synthesis of highly functionalized dihydropyridines using multicomponent reactions (MCRs) at room temperature under catalyst free conditions. The notable features of this protocol are: mild reaction condition, applicability to wide range of substrates, reusability of the PEG and good yields. The interaction of the synthesized compounds with pUC19 plasmid DNA was also analyzed. Some of the synthesized compounds showed interesting functional group dependent nuclease activity for plasmid DNA cleavage under physiological conditions.

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.

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.

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.

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.

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.

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.