Bio-nanoconjugates of lithocholic acid/IR 780 for ROS-mediated apoptosis and optoacoustic imaging applications in breast cancer.

A new lithocholic acid/IR 780 conjugate (LIC) was designed and synthesized for theranostic applications in triple-negative breast cancer. Lithocholic acid is an antitumor biomacromolecule and acts via multiple molecular targets. IR 780 iodide is a fluorescent NIR organic dye researched as a photothermal agent in cancer therapy. A combined conjugate, LIC can have wide applications as a Photothermal/chemotherapeutic and imaging agent in cancer therapy. LIC was characterized and evaluated for its photothermal cytotoxic effect in breast cancer cell lines. Further, to improve the bioavailability of the LIC, a polymeric (PLGA) nanosystem was developed and characterized. The resultant lithocholic acid/IR 780 polymeric nanoconjugates (LIPNCs) were well taken up by the cells and are evident by the inherent red fluorescence of LIC. The LIPNCs also exhibited commendable heat generation when exposed to NIR light (808 nm). The in-vitro anti-cancer studies of LIPNCs also revealed a significant NIR light-based photothermal efficacy (cytotoxic dose 0.75 µM) when compared to the free conjugate (LIC) or the parent moieties. Further cell-based fluorescent and molecular assays showed that LIPNCs induced ROS-mediated apoptotic cell death concurrently being physiologically biocompatible. In-vitro photoacoustic imaging of the LICs exhibited signals comparable to free IR780 dye. Future in vivo studies with LIPNCs or LIC may prove beneficial for developing a promising translational system for its wide application in image-guided cancer theranostics.

Process development for the total synthesis of the novel drug metabolite Carboxy toremifene as a standard reference material along with characterization and purity assessment for the Antidoping quality Control Purposes.

Tamoxifen and toremifene are two selective estrogen receptor modulators (SERMs) commonly used to treat breast cancer in women. Toremifene is well-known as a triphenylethylene derivative. Carboxy toremifene is a common metabolite of toremifene and tamoxifen. Since 2005, the World Anti-Doping Agency (WADA) has banned the SERMs category during in and out of competition. These substances are in the S4 category in the WADA prohibited list as "agents with anti-oestrogenic activity." However, there is no commercially accessible carboxy toremifene reference material in the market. This research highlights the novel synthetic procedure, the development of a carboxy toremifene HPLC method, and validation, along with detailed characterization using advanced analytical techniques using 1 H NMR, HRMS, FT-IR-ATR and UV-visible spectroscopy. RP-HPLC-DAD method was developed and validated to assess the purity of carboxy toremifene. Developed reference material has shown 100% purity. Therefore, we recommend that this synthesized carboxy toremifene may be used as reference material to strengthen the WADA-accredited lab to maintain a clean sports mission during sports competitions.

Controlled creation and annihilation of isolated robust emergent magnetic monopole like charged vertices in square artificial spin ice.

Magnetic analogue of an isolated free electric charge, i.e., a magnet with a single north or south pole, is a long sought-after particle which remains elusive so far. In magnetically frustrated pyrochlore solids, a classical analogue of monopole was observed as a result of excitation of spin ice vertices. Direct visualization of such excitations were proposed and later confirmed in analogous artificial spin ice (ASI) systems of square as well as Kagome geometries. However, such magnetically charged vertices are randomly created as they are thermally driven and are always associated with corresponding equal and opposite emergent charges, often termed as monopole-antimonopole pairs, connected by observable strings. Here, we demonstrate a controlled stabilisation of a robust isolated emergent monopole-like magnetically charged vertices in individual square ASI systems by application of an external magnetic field. The excitation conserves the magnetic charge without the involvement of a corresponding excitation of opposite charge. Well supported by Monte Carlo simulations our experimental results enable, in absence of a true elemental magnetic monopole, creation of electron vortices and studying electrodynamics in presence of a monopole-like field in a solid state environment.

Mitochondrial dynamics quantitatively revealed by STED nanoscopy with an enhanced squaraine variant probe.

Mitochondria play a critical role in generating energy to support the entire lifecycle of biological cells, yet it is still unclear how their morphological structures evolve to regulate their functionality. Conventional fluorescence microscopy can only provide ~300 nm resolution, which is insufficient to visualize mitochondrial cristae. Here, we developed an enhanced squaraine variant dye (MitoESq-635) to study the dynamic structures of mitochondrial cristae in live cells with a superresolution technique. The low saturation intensity and high photostability of MitoESq-635 make it ideal for long-term, high-resolution (stimulated emission depletion) STED nanoscopy. We performed time-lapse imaging of the mitochondrial inner membrane over 50 min (3.9 s per frame, with 71.5 s dark recovery) in living HeLa cells with a resolution of 35.2 nm. The forms of the cristae during mitochondrial fusion and fission can be clearly observed. Our study demonstrates the emerging capability of optical STED nanoscopy to investigate intracellular physiological processes with nanoscale resolution for an extended period of time.

ICT and AIE Characteristics Two Cyano-Functionalized Probes and Their Photophysical Properties, DFT Calculations, Cytotoxicity, and Cell Imaging Applications.

Two probes, AIE-1 and AIE-2, were synthesized to investigate the effect of substitutional functional group on aggregation (aggregation-caused quenching (ACQ) or aggregation-induced emission (AIE)) and intramolecular charge transfer (ICT) behavior as well as on the cell imaging aspect. The yellow-color non-substituted probe AIE-1 showed weak charge-transfer absorption and an emission band at 377 nm and 432 nm, whereas the yellowish-orange color substituted probe AIE-2 showed a strong charge-transfer absorption and an emission band at 424 nm and 477 nm in THF solvent. The UV-Vis studies of AIE-1 and AIE-2 in THF and THF with different water fractions showed huge absorption changes in AIE-2 with high water fractions due to its strong aggregation behavior, but no such noticeable absorption changes were observed for AIE-1. Interestingly, the fluorescence intensity of AIE-1 at 432 nm gradually decreased with increasing water fractions and became almost non-emissive at 90% water. However, the monomer-type emission of AIE-2 at 477 nm was shifted to 584 nm with a 6-fold increase in fluorescence intensity in THF-H2O (1:9, v/v) solvent mixtures due to the restriction of intramolecular rotation on aggregation in high water fractions. This result indicates that the probe AIE-1 shows ACQ and probe AIE-2 shows AIE behaviors in THF-H2O solvent mixtures. Furthermore, the emission spectra of AIE-1 and AIE-2 were carried out in different solvent and with different concentrations to see the solvent- or concentration-dependent aggregation behavior. Scanning electron microscope (SEM) and dynamic light scattering (DLS) experiments were also conducted to assess the morphology and particle size of two probes before and after aggregation. Both of the probes, AIE-1 and AIE-2, showed less toxicity on HeLa cells and were suitable for cell imaging studies. Density functional theory (DFT) calculation was also carried out to confirm the ICT process from an electron-rich indole moiety to an electron-deficient cyano-phenyl ring of AIE-1 or AIE-2.

Monitoring the endocytosis of bovine serum albumin based on the fluorescence lifetime of small squaraine dye in living cells.

Bovine serum albumin (BSA) has a wide range of physiological functions involving the binding, transportation, and delivery of fatty acids, porphyrins, bilirubin, steroids, etc. In the present study, we prepared a small squaraine dye (SD), which can selectively detect BSA using fluorescence lifetime imaging microscopy (FLIM), to monitor the endocytosis of BSA in live cultured cells in real time. This approach revealed that BSA uptake is concentration-dependent in living cells. Furthermore, we used paclitaxel (PTX), a chemotherapeutic drug, to influence the endocytosis of BSA in living cells. The results demonstrated that the endocytic rate was clearly reduced after pretreatment with 0.4 µM PTX for 2 h. The present study demonstrates the potential value of using the fluorescence lifetime of SD to detect BSA concentration and study the physiological mechanism of chemotherapeutic drugs.

Solo Smart Fluorogenic Probe for Potential Cancer Diagnosis and Tracking in Vivo Tumorous Lymphatic Systems via Distinct Emission Signals.

A versatile twisted-intramolecular-charge-transfer (TICT)-based near-infrared (NIR) fluorescent probe (L) has been judiciously designed and synthesized that could be utilized for potential cancer diagnosis and to track lymph node(s) in mice through distinct emission signals. Essentially, the probe rendered the capability to preferentially recognize the cancer cells over the noncancer cells by polarity-guided lipid droplet specific differential bioimaging (in green emission channel) studies. The probe also exhibited selective turn-on fluorescence response toward HSA/BSA in physiological media (aqueous PBS buffer; pH 7.4) at far-red/NIR regions, because of the 1:1 chelation between the probe and HSA/BSA. Therefore, the fluorescent probe was then maneuvered to track the draining lymphatic system and sentinel lymph node in tumor mice model by fluorescence imaging (NIR/deep-red channel), wherein the accumulated albumin protein in the draining tumor lymphatic system facilitated the in situ formation of the fluorescent albumin-L complex.

Fluorescence enhancement of small squaraine dye and its two-photon excited fluorescence in long-term near-infrared I&II bioimaging.

Two-photon excited fluorescence (TPEF) plays an important role in bioimaging, the longer excitation wavelength improves its imaging depths, which gives us deeper biological information. Here, we reported the two-photon absorption of a small squaraine dye (SD), and we found that the TPEF of the small SD can be enhanced significantly using albumin, the TPEF of SD in water was enhanced 17.7 times by adding bull serum albumin (BSA) in the solution. Meanwhile, the cell imaging results indicated that the SD can enter cell effectively in less than 30 min and emit bright TPEF. Furthermore, the SD showed excellent stability against photobleaching in near-infrared II (1200 nm). The cytotoxicity experiment showed that the cytotoxicity of SD is relatively low. Our work demonstrates the excellent two-photon effect of SD in cells, potential application value of SD in two-photon bioimaging, protein detection and near infrared sensing.

Redefining the photo-stability of common fluorophores with triplet state quenchers: mechanistic insights and recent updates.

Light microscopy can offer certain advantages over electron microscopy in terms of acquiring detailed insights into the biological/intra-cellular milieu. In recent years, with the development of new fluorescence imaging technologies, it has become extremely important to assess the role of designing appropriate fluorophores in acquiring desired biological information without encountering any untoward hitches. Over the years, external fluorophores have been prevalently used in fluorescence microscopy and single-molecule fluorescence microscopy-based studies. Photostable fluorogenic probes with high extinction coefficients and quantum yields, exhibiting minimum autofluorescence and photobleaching properties, are preferred in single-molecule microscopy as they can tolerate long-term laser exposure. Therefore, the development of triplet state quenchers and/or any other suitable new strategy to ensure the photo-stability of the fluorophores during long-term live cell imaging exercises is highly anticipated. In this feature article, various strategies for stabilizing fluorophores, including the mechanisms of TSQ-induced stabilization, have been thoroughly reviewed considering contemporary literature reports and applications.

Dual-functional fluorescent molecular rotor for endoplasmic reticulum microviscosity imaging during reticulophagy.

The microviscosity change associated with reticulophagy is an important component for studying endoplasmic reticulum (ER) stress disorders. Here, a BODIPY-arsenicate conjugate 1-based fluorescent molecular rotor was designed to covalently bind vicinal dithiol-containing proteins in the ER, exhibiting a bifunction of reticulophagy initiation and microviscosity evaluation. Therefore, we could quantify the local viscosity changes during reticulophagy based on the fluorescence lifetime changes of probe 1.

Substrate and stereocontrolled iodocycloetherification of highly functionalized enantiomerically pure allylic alcohols: application to synthesis of cytotoxic 2-epi jaspine B and its biological evaluation.

Stereoselectivities of electrophilic additions of molecular iodine to enantiomerically pure highly functionalized allylic alcohols with internal nucleophiles have been investigated. The intramolecular nucleophilic attack on the I2-π complex by an oxygen nucleophile to obtain tri- and tetrasubstituted THFs is highly regio-, stereoselective and substrate controlled. The application of this study has been shown by utilizing one of the THFs 4a as a key intermediate to complete the total synthesis of marine anti-cancer natural product 2-epi jaspine B.

Lattice strain accompanying the colossal magnetoresistance effect in EuB6.

The coupling of magnetic and electronic degrees of freedom to the crystal lattice in the ferromagnetic semimetal EuB(6), which exhibits a complex ferromagnetic order and a colossal magnetoresistance effect, is studied by high-resolution thermal expansion and magnetostriction experiments. EuB(6) may be viewed as a model system, where pure magnetism-tuned transport and the response of the crystal lattice can be studied in a comparatively simple environment, i.e., not influenced by strong crystal-electric field effects and Jahn-Teller distortions. We find a very large lattice response, quantified by (i) the magnetic Grüneisen parameter, (ii) the spontaneous strain when entering the ferromagnetic region, and (iii) the magnetostriction in the paramagnetic temperature regime. Our analysis reveals that a significant part of the lattice effects originates in the magnetically driven delocalization of charge carriers, consistent with the scenario of percolating magnetic polarons. A strong effect of the formation and dynamics of local magnetic clusters on the lattice parameters is suggested to be a general feature of colossal magnetoresistance materials.

A tunable strain sensor using nanogranular metals.

This paper introduces a new methodology for the fabrication of strain-sensor elements for MEMS and NEMS applications based on the tunneling effect in nano-granular metals. The strain-sensor elements are prepared by the maskless lithography technique of focused electron-beam-induced deposition (FEBID) employing the precursor trimethylmethylcyclopentadienyl platinum [MeCpPt(Me)(3)]. We use a cantilever-based deflection technique to determine the sensitivity (gauge factor) of the sensor element. We find that its sensitivity depends on the electrical conductivity and can be continuously tuned, either by the thickness of the deposit or by electron-beam irradiation leading to a distinct maximum in the sensitivity. This maximum finds a theoretical rationale in recent advances in the understanding of electronic charge transport in nano-granular metals.