Excitation wavelength-dependent quantum yield in water-soluble CdTe quantum dots.

The quantum yield (QY) of semiconductor quantum dots (QDs) is severely hampered by the inherent fluorescence intermittency. The QY of QDs typically increases with an increase in the excitation wavelength. Here, we present a distinctive behavior, where the QY is found to decrease with an increase in the excitation wavelength in water-soluble CdTe QDs (CQDs).

NIR emissive probe for fluorescence turn-on based dead cell sorting and viscosity mapping in .

Dead cell sorting is pivotal and plays a very significant role in homeostasis. Apoptosis and ferroptosis are the two major regulatory cell death processes. Apoptosis is a programmed cell death process, while ferroptosis is a regulatory cell death process.

A zinc metal complex as an NIR emissive probe for real-time dynamics and embryogenic evolution of lysosomes using super-resolution microscopy.

Zinc (Zn) based fluorescent metal complexes have gained increasing attention due to their non-toxicity and high brightness with marked fluorescence quantum yield (QY). However, they have rarely been employed in super-resolution microscopy (SRM) to study live cells and dynamics of lysosomes. Here, we present an NIR emissive highly photostable Zn-complex as a multifaceted fluorescent probe for the long-term dynamical distribution of lysosomes in various cancerous and non-cancerous cells in live condition and embryogenic evolution in ().

Assessing the overflowing pile-up effect on the photoluminescence lifetime of nanomaterials.

The tunable complex emissive states with nanosecond to microsecond lifetimes in nanomaterials, arise due to their structural heterogeneity, enabling them with a wide range of advanced optoelectronic applications. However, understanding the complex photoluminescence lifetime in these nanomaterials is critically challenged by the overflowing pile-up effect, which occurs due to the high repetition rate of the light source in the time-correlated single photon counting (TCSPC) technique. Here, we provide a quantitative lifetime analysis, especially in metal nanoclusters, metal complexes, and semiconductor quantum dots, which suggests that the same experimental parameters can mislead the lifetime data interpretation for long-ranged luminescent nanomaterials.

One-Pot Synthesis of 1, 2-Dihydro [1,2,4] Triazinium Salt by Copper-Assisted Unprecedented Cyclization Reaction: Applications in DNA and Protein Interaction Studies.

Copper catalyzed intramolecular annulation of 2-((2-benzylidene-1-phenylhydrazineyl)methyl)pyridine derivatives was described. It was found that Cu(II) is reduced under the reaction condition to Cu(I). Synthesized 1,2-dihydro [1,2,4] triazinium salt showed fluorescence activity in the solid state.

NIR-emissive carbon nanodots as a tool to mark ribosomal RNA and nucleolus components using super-resolution microscopy.

Ribosomal RNA (rRNA) plays a key role in protein synthesis and ribosomal biogenesis. The exclusively used commercial dye for RNA staining is SYTO RNASelect, which works in fixed cells only. To overcome this constraint, we synthesized NIR-emissive, highly photostable, and biocompatible carbon nanodots (CNDs) as a fluorescent biomarker for rRNA.

Super-Resolution Microscopy Unveils Synergistic Structural Changes of Organelles Upon Point Mutation.

Ethyl methanesulphonate (EMS), is a widely used chemical mutagen that causes high-frequency germline null mutation by inserting an alkyl group into the nucleotide guanine in eukaryotic cells. The effect of EMS on the dynamics of the aneuploid genome, increased cellular instability, and carcinogenicity in relation to benign and malignant tumors are reported, but the molecular level understanding of morphological changes of higher-order chromatin structure has poorly been understood. This is due to a lack of sufficient resolution in conventional microscopic techniques to see small structures below the diffraction limit.

Tracking the super resolved structure of mitochondria using red emissive carbon nanodots as a fluorescent biomarker.

Herein, we report new red emissive highly photostable and water-soluble carbon nanodots (TPP CNDs) to visualize mitochondrial dynamics using super-resolution radial fluctuations (SRRF) microscopy. The TPP CNDs were synthesized in a one-step method, using 3-(carboxypropyl)triphenylphosphonium bromide (TPP) and -phenylenediamine (OPDA) as precursors. The obtained crystal structure, NMR, and mass data suggested the presence of [3-(1-benzimidazol-2-yl)propyl](triphenyl)phosphonium bromide (CHNPBr) as a molecular fluorophore (MF) on the surface of the TPP CNDs.

Unveiling the Long-Lived Emission of Copper Nanoclusters Embedded in a Protein Scaffold.

Protein-conjugated coinage metal nanoclusters have become promising materials for optoelectronics and biomedical applications. However, the origin of the photoluminescence, especially the long-lived excited state emission in these metal nanoclusters, is still elusive. Here, we unveiled the underlying mechanism of long-lived emission in albumin protein-conjugated copper nanoclusters (Cu NCs) using steady state and time-resolved spectroscopic techniques.

Design and synthesis of novel palladium cyclometallate-based fluorescent probe: Studies on interaction with cell membrane by confocal and fluorescence lifetime imaging.

Coordination complexes offer great potential as cellular imaging probes, which allow to examine specific cell organelle structures in their physiological conditions to better understand the biological system. Understanding the heterogeneous nature of the cell membrane could unveil details of their functionality. Here, we have developed a new anthracene conjugated fluorescent palladium(II) cyclometallate [PdLCl] where LH = [2-(2- (anthracen-9-ylmethylene)-1-phenylhydrazineyl)pyridine] (H stands for dissociable proton), which not only specifically stains the cell membrane, but could be utilized to visualise the membrane by the confocal and fluorescence lifetime imaging microscopy (FLIM).

Mapping the time dependent DNA fragmentation caused by doxorubicin loaded on PEGylated carbogenic nanodots using fluorescence lifetime imaging and superresolution microscopy.

Doxorubicin is an anthracycline drug most commonly used in cancer therapy. It intercalates with the nuclear DNA and induces toxicity by causing DNA breaks and histone eviction. However, the kinetics of its action on the nucleus has not been mapped effectively.

SARS-CoV-2 Spike mutations modify the interaction between virus Spike and human ACE2 receptors.

The high mutability of the SARS-CoV-2 virus is a growing concern among scientific communities and health professionals since it brings the effectiveness of repurposed drugs and vaccines for COVID-19 into question. Although the mutational investigation of the Spike protein of the SARS-CoV-2 virus has been confirmed by many different researchers, there is no thorough investigation carried out at the interacting region to reveal the mutational status and its associated severity. All the energetically favorable mutations and their detailed analytical features that could impact the infection severity of the SARS-CoV-2 virus need to be identified.

Structural and spectroscopic characterization of pyrene derived carbon nano dots: a single-particle level analysis.

The bottom-up approach has been widely used for large-scale synthesis of carbon nanodots (CNDs). However, the structure and origin of photoluminescence in CNDs synthesized by the bottom-up approach is still a subject of debate. Here, using a series of separation techniques like solvent extraction, column chromatography, gel electrophoresis and dialysis, we present three distinct fluorescent components in CNDs synthesized from pyrene, a well-known precursor molecule.

Development of a Highly Specific, Selective, and Sensitive Fluorescent Probe for Detection of Mycobacteria in Human Tissues.

Tuberculosis (TB), including extrapulmonary TB, is responsible for more than one million deaths in a year worldwide. Existing methods of mycobacteria detection have poor sensitivity, selectivity, and specificity, especially in human tissues. Herein, the synthesis of a cholic acid-derived fluorescent probe (P4) that can specifically stain the mycobacterium species is presented.

Effect of Protein Corona on the Drug Delivery of Carbogenic Nanodots and Their Mapping by Fluorescence Lifetime Imaging Microscopy.

It is practically impossible to avoid the nonspecific binding of protein to a nanocarrier when it enters a biological fluid. This hinders the chemotherapeutic efficacy of the nanocarrier to a large extent. Surface functionalization, in the recent past, helped in reducing such nonspecific interactions.

Super-Resolution Microscopy Revealed the Lysosomal Expansion During Epigallocatechin Gallate-Mediated Apoptosis.

Direct visualization of the dynamic events in lysosomes during drug-mediated programmed cell death (apoptosis) is a great challenge. This is due to the lack of resolving power of a conventional microscope and also the unavailability of a suitable multimodal probe that simultaneously can carry the drug with high loading capacity and ensure its specific internalization into lysosomes. In this work, using super-resolution microscopy, we observed the lysosomal expansion during apoptosis that was treated with epigallocatechin gallate (EGCG) conjugated to bovine serum albumin (BSA).

Structural Decoding of a Small Molecular Inhibitor on the Binding of SARS-CoV-2 to the ACE 2 Receptor.

Inhibition of the interaction of the receptor-binding domain (RBD) of the spike protein and the human angiotensin-converting enzyme 2 (ACE 2) receptor is the most effective therapeutic formulation to restrict the contagious respiratory illness and multiple organ failure caused by the novel SARS-CoV-2 virus. Based on the structural decoding of the RBD of the spike protein, here we have generated a new set of small molecules that have strong inhibiting properties on the binding of the spike protein to ACE 2 receptors. These small-molecule inhibitors surprisingly show binding to the main protease, nucleoprotein, and RNA-dependent RNA polymerase, which are the other responsible factors for the viral infection.

Absorption and emission of light in red emissive carbon nanodots.

The structure-function relationship, especially the origin of absorption and emission of light in carbon nanodots (CNDs), has baffled scientists. The multilevel complexity arises due to the large number of by-products synthesized during the bottom-up approach. By performing systematic purification and characterization, we reveal the presence of a molecular fluorophore, quinoxalino[2,3-]phenazine-2,3-diamine (QXPDA), in a large amount (∼80% of the total mass) in red emissive CNDs synthesized from -phenylenediamine (OPDA), which is one of the well-known precursor molecules used for CND synthesis.

Fluorescent Probes for Super-Resolution Microscopy of Lysosomes.

Lysosomes are membrane-enclosed small spherical cytoplasmic organelles. Malfunctioning and abnormalities in lysosomes can cause a plethora of neurodegenerative diseases. Consequently, understanding the structural information on lysosomes down to a subnanometer level is essential.

Magnetofluorescent Nanoprobe for Multimodal and Multicolor Bioimaging.

Although, superparamagnetic iron oxide nanoparticles (SPIONs) have extensively been used as a contrasting agent for magnetic resonance imaging (MRI), the lack of intrinsic fluorescence restricted their application as a multimodal probe, especially in combination with light microscopy. In Addition, the bigger size of the particle renders them incompetent for bioimaging of small organelles. Herein, we report, not only the synthesis of ultrasmall carbon containing magneto-fluorescent SPIONs with size ∼5 nm, but also demonstrate its capability as a multicolor imaging probe.

Direct visualization of the protein corona using carbon nanodots as a specific contrasting agent.

The cellular uptake of the nanoparticles is greatly affected by the formation of protein corona. As a result, an in-depth knowledge of direct visualization of the corona and quantification thereof is extremely important. Although transmission electron microscopy is one of the best techniques for visualization, the heavy metals that are used to increase the contrast of protein are non-specific and may lead to artifacts and erroneous conclusions.

Intrinsically disordered proteins of viruses: Involvement in the mechanism of cell regulation and pathogenesis.

Intrinsically disordered proteins (IDPs) possess the property of inherent flexibility and can be distinguished from other proteins in terms of lack of any fixed structure. Such dynamic behavior of IDPs earned the name "Dancing Proteins." The exploration of these dancing proteins in viruses has just started and crucial details such as correlation of rapid evolution, high rate of mutation and accumulation of disordered contents in viral proteome at least understood partially.

Bovine Serum Albumin-Conjugated Red Emissive Gold Nanocluster as a Fluorescent Nanoprobe for Super-resolution Microscopy.

The gold nanocluster (GNC), because of its interesting photoluminescence properties and easy renal clearance from the body, has tremendous biomedical applications. Unfortunately, it has never been explored for super-resolution microscopy (SRM). Here, we present a protein-conjugated red emissive GNC for super-resolution radial fluctuation (SRRF) of the lysosome in HeLa cells.

Serum albumin-mediated strategy for the effective targeting of SARS-CoV-2.

Novel coronavirus (NCoV-19), also known as SARS CoV-2, is a pathogen causing an emerging infection that rapidly increases in incidence and geographic range, is associated with the ever-increasing morbidity and mortality rates, and shows sever economic impact worldwide. The WHO declares the NCoV-19 infection disease (COVID-19) a Public Health Emergency of International Concern on 30 January 2020 and subsequently, on March 11, 2020, declared it a Global Pandemic. Although some people infected with SARS CoV-2 have no symptoms, the spectrum of symptomatic infection ranges from mild to critical, with most COVID-19 infections being not severe.