Hypoxia: Intriguing Feature in Cancer Cell Biology.

Hypoxia, a key aspect of the tumor microenvironment, plays a vital role in cell proliferation, angiogenesis, metabolism, and the immune response within tumors. These factors collectively promote tumor advancement, aggressiveness, metastasis and result in a poor prognosis. Hypoxia inducible factor 1α (HIF-1α), activated under low oxygen conditions, mediates many of these effects by altering drug target expression, metabolic regulation, and oxygen consumption. These changes promote cancer cell growth and survival. Hypoxic tumor cells develop aggressive traits and resistance to chemotherapy and radiotherapy, leading to increased mortality. Targeting hypoxic tumor offers a potential solution to overcome the challenges posed by tumor heterogeneity and can be used in designing diagnostic and therapeutic nanocarriers for various solid cancers. This concept provides an overview of the intricate relationship between hypoxia and the tumor microenvironment, highlighting its potential as a promising tool for cancer therapies. The article explores the development of hypoxia in cancer cells and its role in cancer progression, along with the latest advancements in hypoxia-triggered cancer treatment.

Selective Sensing of Epinephrine by Phenylboronic Acid Tethered Carbon Dot.

The present work depicts development of phenylboronic acid (PBA) derived and appended carbon dots (CD1-PBAs) to detect epinephrine with high sensitivity and selectivity against structurally analogous biomolecules like norepinephrine, L-Dopa and glucose. Carbon dots were synthesized by hydrothermal method. Microscopic and spectroscopic studies ensured the suitability of CD1-PBAs for diol sensing. Catecholic-OH groups of epinephrine primarily form covalent adduct with CD1-PBAs via boronate-diol linkage that caused change in absorption intensity of CD1-PBAs. The limit of detection (LOD) for epinephrine was found to be 2.0 nM. For other analogous biomolecules, formation of boronate-diol linkage might have got retarded by the dominant participation of secondary interactions like hydrogen bonding owing to the presence of varying functional moieties. Subsequently, responsiveness in the change in absorbance intensity of CD1-PBAs was weaker compared to that for epinephrine. Hence, a selective and efficient carbon dot (CD1-PBAs) based epinephrine sensor was developed simply by utilizing boronate-diol linkage.

Peptide Amphiphilic Supramolecular Nanogels: Competent Host for Notably Efficient Lipase-Catalyzed Hydrolysis of Water-Insoluble Substrates.

The present work depicts the development of stable nanogels in an aqueous medium that were exploited for efficient surface-active lipase-catalyzed hydrolysis of water-insoluble substrates. Surfactant-coated gel nanoparticles (neutral NG1, anionic NG2, and cationic NG3) were prepared from peptide amphiphilic hydrogelator (G1, G2, and G3, respectively) at different hydrophilic and lipophilic balance (HLB). Chromobacterium viscosum (CV) lipase activity towards hydrolysis of water-insoluble substrates (p-nitrophyenyl-n-alkanoates (C4-C10)) in the presence of nanogels got remarkably improved by ~1.7-8.0 fold in comparison to that in aqueous buffer and other self-aggregates. An increase in hydrophobicity of the substrate led to a notable improvement in lipase activity in the hydrophilic domain (HLB>8.0) of nanogels. The micro-heterogeneous interface of small-sized (10-65 nm) nanogel was found to be an appropriate scaffold for immobilizing surface-active lipase to exhibit superior catalytic efficiency. Concurrently, the flexible conformation of lipase immobilized in nanogels was reflected in its secondary structure having the highest α-helix content from the circular dichroism spectra.

Co2+ Doped Biotinylated Carbon Dot: A Theranostic Agent for Target Specific Killing of Cancer Cells via Hypoxia Induced Apoptosis.

Conventional cancer treatments have systematic side effects that stand against its desirable therapeutic efficacy. Alternative strategies using biochemical features of cancer cells to promote apoptosis are finding notable significance. One such important biochemical feature of malignant cells is hypoxia, alteration of which can lead to cell death. Hypoxia inducible factor 1α (HIF-1α) has the key role in hypoxia generation. Herein, we synthesized biotinylated Co2+ -integrated carbon dot (CoCDb ) that specifically diagnose and selectively killed cancer cells with 3-3.1-fold higher efficiency over non-cancer cells by hypoxia induced apoptosis in absence of traditional therapeutic intervention. Immunoblotting assay in CoCDb treated MDA-MB-231 cells confirmed the increased expression of HIF-1α that was responsible for efficient killing of cancer cells. In 2D cells and 3D tumor spheroid, CoCDb treated cancer cells showed significant apoptosis that make CoCDb a potential theranostic agent.

Folic Acid-Functionalized Carbon Dot-Enabled Starvation Therapy in Synergism with Paclitaxel against Breast Cancer.

Glucose oxidase (GOx)-induced cancer starvation has recently emerged for halting the abnormal proliferation of triple-negative breast cancer (TNBC). However, monotherapy with GOx or a conventional chemotherapeutic displays suboptimal efficacy in eliminating tumors and poses impending risks to healthy tissues. To augment therapeutic efficacy and tumor selectivity, folic acid (FA)-functionalized carbon dots (CDs) embedded with GOx and paclitaxel (PTX) [FA-CD-(PTX-GOx)] was developed that showed the efficient killing of TNBC, MDA-MB-468 cells over noncancerous HEK 293 cells through synergistic effects of cancer starvation-induced oxidative stress and chemotherapy. The cargo-laden FA-CD complex resulted in a 4-8 fold increase in cancer cell death at 60 µg/mL when compared to standalone therapy with the native compounds and individually loaded cargo on FA-CD. This improved cancer cell killing efficacy of the FA-CD-(PTX-GOx) complex could be endorsed by folate receptor (FR)-mediated target-specific cellular internalization of the FA-CD complex. The antitumorigenic efficacy of the FA-CD-(PTX-GOx) complex was further validated in a three-dimensional (3D) breast tumor spheroid model. A significant 4.5-fold reduction in spheroid dimension along with antiproliferation was observed with time up to 72 h following exposure to the FA-CD-(PTX-GOx) complex. This antitumorigenic potential of FA-CD-(PTX-GOx) could be attributed to the enhanced intratumoral reactive oxygen species generation following glucose depletion by GOx that has been facilitated by the chemotherapeutic efficacy of PTX resulting in the efficient killing of cancer cells. The present study provides a novel strategy of FR-mediated fluorescent CD-enabled combined formulation of GOx and PTX for the target-specific superior killing of TNBC cells in the synergism of glucose starvation with chemotherapy.

Naphthalimide-Based Azo-Functionalized Supramolecular Vesicle in Hypoxia-Responsive Drug Delivery.

Supramolecular materials that respond to external triggers are being extensively utilized in developing spatiotemporal control in biomedical applications ranging from drug delivery to diagnostics. The present article describes the development of self-assembled vesicles in 1:9 (v/v), tetrahydrofuran (THF)-water by naphthalimide-based azo moiety containing amphiphile (NI-Azo) where azo moiety would act as the stimuli-responsive junction. The self-assembly of NI-Azo took place through H-type of aggregation. Microscopic and spectroscopic analyses confirmed the formation of supramolecular vesicles with a dimension of 200-250 nm. Azo (-N═N-) moiety is known to get reduced to amine derivatives in the presence of the azoreductase enzyme, which is overexpressed in the hypoxic microenvironment. The absorbance intensity of this characteristic azo (-N═N-) moiety of NI-Azo (1:9 (v/v), THF-water) at 458 nm got diminished in the presence of both extracellular and intracellular bacterial azoreductase extracted from Escherichia coli bacteria. The same observation was noted in the presence of sodium dithionite (mimic of azoreductase), indicating that azoreductase/sodium dithionite induced azo bond cleavage of NI-Azo, which was confirmed by matrix-assisted laser desorption ionization time-of-flight spectrometric data of the corresponding aromatic amine fragments. The anticancer drug, curcumin, was encapsulated inside NI-Azo vesicles that successfully killed B16F10 cells (cancer cells) in CoCl2-induced hypoxic environment owing to the azoreductase-responsive release of drug. The cancer cell killing efficiency by curcumin-loaded NI-Azo vesicles in the hypoxic condition was 2.15-fold higher than that of the normoxic environment and 2.4-fold higher compared to that of native curcumin in the hypoxic condition. Notably, cancer cell killing efficiency of curcumin-loaded NI-Azo vesicles was 4.5- and 1.9-fold higher than that of noncancerous NIH3T3 cells in normoxic and hypoxic environments, respectively. Cell killing was found to be primarily through the early apoptotic pathway.

Nipecotic-Acid-Tethered, Naphthalene-Diimide-Based, Orange-Emitting Organic Nanoparticles as Targeted Delivery Vehicle and Diagnostic Probe toward GABAA-Receptor-Enriched Cancer Cells.

This article demonstrates target-specific cellular imaging of GABA (γ-aminobutyric acid) receptor (GABAAR)-enriched cells (SH-SY5Y and A549) with therapeutic efficacy by naphthalene diimide (NDI)-derived fluorescent organic nanoparticles (FONPs). Self-assembly-driven formation of spherical organic particles by nipecotic-acid-tethered l-aspartic acid appended NDI derivative (NDI-nip) took place in DMSO-water through J-type aggregation. NDI-nip having a naphthyl residue and a nipecotic acid unit at both terminals exhibited aggregation-induced emission (AIE) at and above 60% water content in DMSO because of excimer formation at λem = 579 nm. The orange-emitting NDI-nip FONPs (1:99 v/v DMSO-water) having excellent cell viability and high photostability were used for selective bioimaging and killing of GABAAR-overexpressed cancer cells through target-specific delivery of the anticancer drug curcumin. The fluorescence intensity of NDI-nip FONPs were quenched in GABAAR-enriched neuroblastoma cells (SH-SY5Y) and cancerous cells (A549). Notably, in the presence of GABA, the NDI-nip FONPs exhibited their native fluorescence within the same cell lines. Importantly, no such quenching and regaining of NDI-nip FONP emission in the presence of GABA was noted in the case of the noncancerous cell NIH3T3. The killing efficiency of curcumin-loaded NDI-nip FONPs ([curcumin] = 100 µM and [NDI-nip FONPs] = 50 µM) was significantly higher in the cases of SH-SY5Y (88 ± 3%) and A549 (72 ± 2%) than in NIH3T3 (37 ± 2). The presence of a nipecotic acid moiety facilitated the selective cellular internalization of NDI-nip FONPs into GABAAR-overexpressing cells. Hence, these orange-emitting NDI-nip FONPs may be exploited as a targeted diagnostic probe as well as a drug delivery vehicle for GABAAR-enriched cancer cells.

Paclitaxel-Loaded Biotinylated Fe2+-Doped Carbon Dot: Combination Therapy in Cancer Treatment.

The present research work delineates the design and preparation of covalently tailored biotinylated Fe2+-doped carbon dots (FCDb). The FCDb was successfully used as a pro-drug activator, diagnostic probe, and target-specific delivery vehicle for anticancer drug paclitaxel in pro-drug-free drug combination therapy of cancer treatment. Fe2+-doped carbon dot was synthesized via the hydrothermal method (FCD). The surface of FCD was covalently modified with cancer cell targeting ligand biotin (FCDb). Microscopic and spectroscopic methods were used to characterize aqueous soluble FCD and FCDb. Both FCD and FCDb emit blue fluorescence under UV light irradiation. FCD and FCDb can effectively sense H2O2 by fluorescence quenching as well as activate H2O2 (pro-drug), which oxidatively damage the DNA through the generation of reactive oxygen species (ROS: superoxide (O2•-), hydroxyl radical (•OH), etc). Both FCD and FCDb were utilized as selective cellular markers for cancer cell B16F10 owing to their high H2O2 content, which was more distinct in the case of FCDb due to the overexpression of biotin receptor in cancer cell. Anticancer drug paclitaxel (PTX)-loaded FCDb (FCDb-PTX) was employed for the selective killing of B16F10 cancer cells. This pro-drug-free drug formulation (FCDb-PTX) exhibited ∼2.7- to 3.5-fold higher killing of B16F10 cells mostly via early as well as late apoptotic path in comparison to noncancer NIH3T3 cells through the synergistic action of ROS (generated from H2O2 in the presence of FCDb) and anticancer effect of PTX. Hence, this newly developed FCDb-PTX can act as a potential theranostic agent in the domain of combination therapy of cancer treatment.

Naphthalimide based fluorescent organic nanoparticles in selective sensing of Fe3+ and as a diagnostic probe for Fe2+/Fe3+ transition.

Fluorescent organic nanoparticles (FONPs) have attracted considerable attention as a practical and effective platform for sensing and imaging applications. The present article delineates the fabrication of FONPs derived from the naphthalimide based histidine appended amphiphile, NID. The self-assembly of NID in 99 vol% water in DMSO led to the formation of FONPs through J-type aggregation. Aggregation-induced emission (AIE) was observed due to the pre-associated excimer of NID with bluish green emission at 470 nm along with intramolecular charge transfer (ICT). The emission of NID FONPs was utilized for selective sensing of Fe3+ and bioimaging of Fe3+ inside mammalian cells. The fluorescence intensity of the FONPs was quenched with the gradual addition of Fe3+ due to the formation of a 1 : 1 stoichiometric complex with the histidine residue of NID. The morphology of the FONPs transformed from spherical to spindle upon the complex formation of NID with Fe3+. The limit of detection (LOD) of this AIE based turn-off chemosensor for Fe3+ was found to be 12.5 ± 1.2 µM having high selectivity over other metal ions. On the basis of the very low cytotoxicity and selective sensing of Fe3+, NID FONPs were successfully employed for bioimaging of Fe3+ ions through fluorescence quenching within mammalian cells (NIH3T3, B16F10). Considering the varying oxidative stress inside different cells, NID FONPs were used for detecting Fe2+ to Fe3+ redox state transition selectively inside cancer cells (B16F10) in comparison to non-cancerous cells (NIH3T3). Selective sensing of cancer cells was substantiated by co-culture experiment and flow cytometry. Hence, NID FONPs can be a selective diagnostic probe for cancer cells owing to their higher H2O2 content.

Morphological transformation of self-assemblies by tuning hydrophobic segment of small amphiphiles.

HYPOTHESIS: With increasing surge in the development of supramolecular self-assemblies, it is crucial to predict the influence of amphiphilic segment in dictating the morphology of self-aggregates. This article reports the design and synthesis of low molecular weight amphiphiles with varying hydrophobicity both in the spacer unit and at the terminal moiety. EXPERIMENTS: Hydrophobicity at the spacer moiety was modulated by altering alkyl chain length and by inclusion of aromatic ring and the same was changed at hydrophobic terminal using pyrene, naphthalene, n-hexadecane having 2-aminopyridine as polar head. Microscopy and spectroscopy were used to investigate the morphologies of self-aggregated amphiphiles. FINDINGS: Variation of hydrophobicity of the spacer moiety either by changing the alkyl chain length (C0, C2, C6, C11 and phenyl ring) having pyrene as terminal hydrophobic unit led to the formation of only spherical vesicles in respective solvent system. Morphological transformation of self-aggregates from vesicle to fused-vesicle to gel was observed in DMSO-water upon alteration in the hydrophobic end of amphiphile from pyrene to naphthyl to C16 alkyl chain having C6 alkyl chain as spacer. Hence, the hydrophobicity at the terminal of the amphiphile has the predominant role in tuning the morphology of self-aggregates through modulation in the hydrophobic-lipophilic balance (HLB) of amphiphiles.

Photosensitizer Tailored Surface Functionalized Carbon Dots for Visible Light Induced Targeted Cancer Therapy.

Herein, a photosensitizer (riboflavin) tailored surface functionalized carbon dot (RCD1s) was designed to utilize it in visible light induced targeted cancer therapy. At first, phenylboronic acid appended biotinylated blue emitting carbon dot (CD1s) was synthesized. Riboflavin having "diol" moiety was covalently linked with this CD1s to prepare RCD1s by using complementary boronate-diol linkage. Lewis acid-base interaction facilitated the covalent linkage formation between the surface functionalizing agent of CD1s and riboflavin to develop water-soluble, green emitting RCD1s. Interestingly, this newly synthesized RCD1s has the ability to produce reactive oxygen species (ROS) such as hydroxyl and superoxide radicals under exposure of visible light (wavelength: 460-490 nm). These ROS also can destroy the structure of DNA by oxidative pathway. Thus, under irradiation of visible light (wavelength: 460-490 nm), RCD1s was found to kill HeLa and B16F10 melanoma cells over noncancer cell NIH3T3 by ∼5-fold higher efficacy through ROS induced oxidative DNA damage. The presence of biotin on the surface of the riboflavin tethered carbon dot is essential for the selective killing of cancer cells over normal cells. In the presence of UV light (340-420 nm), RCD1s showed no notable killing of cancer cells as well as normal cells. Besides, RCD1s in the presence of visible light selectively stained HeLa and B16F10 cells over noncancerous cell NIH3T3 by exploiting its fluorescence and cancer cell targeting moiety, biotin. Hence, the newly developed RCD1s can be utilized in theranostic applications including bioimaging and selective killing of cancer cells in the presence of visible light (460-490 nm).