Targeted Chemo-Phototherapy in Red Light with Novel Doxorubicin and Iron(III) Complex-Functionalized Gold Nanoconjugate (Dox-Fe@FA-AuNPs)

The anticancer efficacy of doxorubicin, an anthracycline-based and FDA-approved chemotherapeutic drug, is significantly hindered by acquired chemoresistance and severe side effects despite its potent anticancer properties. To overcome these challenges, we developed an innovative therapeutic formulation that integrates targeted chemotherapy and phototherapy within a single platform using gold nanoparticles (AuNPs). This novel nanoconjugate, designated as Dox-Fe@FA-AuNPs, is co-functionalized with folic acid, doxorubicin, and an iron(III)-phenolate/carboxylate complex, enabling cancer-specific drug activation. Here, we report the synthesis, characterization, and comprehensive physico-chemical and biological evaluations of Dox-Fe@FA-AuNPs. The nanoconjugate exhibited excellent solubility, stability, and enhanced cellular uptake in folate receptor-positive cancer cells. The nanoconjugate was potently cytotoxic against HeLa and MDA-MB-231 cancer cells (HeLa: 105.5±16.52 μg mL-1; MDA-MB-231: 112.0±12.31 μg mL-1; MDA-MB-231 (3D): 156.31±19.35 μg mL-1) while less cytotoxic to the folate(-) cancer cells (MCF-7, A549 and HepG2). The cytotoxicity was attributed to the pH-dependent release of doxorubicin, which preferentially occurs in the acidic tumor microenvironment. Additionally, under red light irradiation, the nanoconjugate generated ROS, inducing caspase-3/7-dependent apoptosis with a photo-index (PI) >50, and inhibited cancer cell migration. Our findings underscore the potential of Dox-Fe@FA-AuNPs as a highly effective and sustainable platform for targeted chemo-phototherapy.

Red light-activable biotinylated copper(II) complex-functionalized gold nanocomposite (Biotin-Cu@AuNP) towards targeted photodynamic therapy

We report the synthesis and characterization of red-light activable gold nanoparticle functionalized with biotinylated copper(II) complex of general molecular formula, [Cu(L³)(L⁶)]-AuNPs (Biotin-Cu@AuNP), where L³ = N-(3-((E)-3,5-di-tert-butyl-2-hydroxybenzylideneamino)-4-hydroxyphenyl)-5-((3aS,4S,6aR)-2-oxo-hexahydro-1H-thieno[3,4-d]imidazol-4-yl)pentanamide, L⁶ = 5-(1,2-dithiolan-3-yl)-N-(1,10-phenanthrolin-5-yl)pentanamide, which was explored for their photophysical, theoretical and photo-cytotoxic potentials. The nanoconjugate exhibits differential uptake in biotin positive and biotin negative cancer cells as well as normal cells. The nanoconjugate also shows remarkable photodynamic activity against biotin positive A549 (IC₅₀: 13 μg/mL in red light; >150 μg/mL in dark) and HaCaT (IC₅₀: 23 μg/mL in red light; >150 μg/mL in dark) cells under red light (600-720 nm, 30 Jcm^-2) irradiation, with significantly high photo-indices (PI>15). The nanoconjugate is less toxic to HEK293T (biotin negative) and HPL1D (normal) cells. Confocal microscopy confirms preferential mitochondrial and partly cytoplasmic localization of Biotin-Cu@AuNP in A549 cells. Several photo-physical and theoretical studies reveal the red light-assisted generation of singlet oxygen (¹O₂) (Ф (¹O₂) =0.68) as a reactive oxygen species (ROS) which results in remarkable oxidative stress and mitochondrial membrane damage, leading to caspase 3/7-dependent apoptosis of A549 cells. Overall, the nanocomposite (Biotin-Cu@AuNP) exhibiting red light-assisted targeted photodynamic activity has emerged as the ideal next generation PDT agents.

La(iii)–curcumin-functionalized gold nanocomposite as a red light-activatable mitochondria-targeting PDT agent

Functionalization of La(iii)–curcumin to gold nanoparticles resulted in remarkable red-shifted UV-visible absorption and exhibited remarkable differential photodynamic ability towards cancer cells upon red-light activation.

Computational Studies of Selected Transition Metal Complexes as Potential Drug Candidates against the SARS-CoV-2 Virus

The earth has witnessed the greatest global health crisis due to the outbreak of the SARS-CoV-2 virus in late 2019, resulting in the pandemic COVID-19 with 3.38 million mortality and 163 million infections across 222 nations. Therefore, there is an urgent need for an effective therapeutic option against the SARS-CoV-2 virus. Transition metal complexes with unique chemical, kinetic and thermodynamic properties have recently emerged as the viable alternative for medicinal applications. Herein, the potential application of selected antiviral transition metal-based compounds against the SARS-CoV-2 virus was explored in silico. Initially, the transition metal-based antiviral compounds (1-5) were identified based on the structural similarity of the viral proteins (proteases, reverse transcriptase, envelop glycoproteins, etc.) of HIV, HCV, or Influenza virus with the proteins (S-protein, RNA-dependent RNA polymerase, proteases, etc) of SARS-CoV-2 virus. Hence the complexes (1-5) were subjected to ADME analysis for toxicology and pharmacokinetics report and further for the molecular docking calculations, selectively with the viral proteins of the SARS-CoV-2 virus. The molecular docking studies revealed that the iron-porphyrin complex (1) and antimalarial drug, ferroquine (2) could be the potential inhibitors of Main protease (Mpro) and spike proteins respectively of SARS-CoV-2 virus. The complex 1 exhibited high binding energy of -11.74 kcal/mol with the Mpro of SARS-CoV-2. Similarly ferroquine exhibitred binding energy of -7.43 kcal/mol against spike protein of SARS-CoV-2. The complex 5 also exhibited good binding constants values of -7.67, -8.68 and -7.82 kcal/mol with the spike protein, Mpro and RNA dependent RNA polymerase (RdRp) proteins respectively. Overall, transition metal complexes could provide an alternative and viable therapeutic solution for COVID-19.

Iron(III) Complex-Functionalized Gold Nanocomposite as a Strategic Tool for Targeted Photochemotherapy in Red Light

Iron(III)-phenolate/carboxylate complexes exhibiting photoredox chemistry and photoactivated reactive oxygen species (ROS) generation at their ligand-to-metal charge-transfer (LMCT) bands have emerged as potential strategic tools for photoactivated chemotherapy. Herein, the synthesis, in-depth characterization, photochemical assays, and remarkable red light-induced photocytotoxicities in adenocarcinomic human immortalized human keratinocytes (HaCaT) and alveolar basal epithelial (A549) cells of iron(III)-phenolate/carboxylate complex of molecular formula, [Fe(L¹)(L²)] (1), where L¹ is bis(3,5 di-tert-butyl-2-hydroxybenzyl)glycine and L² is 5-(1,2-dithiolan-3-yl)-N-(1,10-phenanthroline-5-yl)pentanamide, and the gold nanocomposite functionalized with complex 1 (1-AuNPs) are reported. There was a significant red shift in the UV-visible absorption band on functionalization of complex 1 to the gold nanoparticles (λ_max: 573 nm, 1; λ_max: 660 nm, 1-AuNPs), rendering the nanocomposite an ideal candidate for photochemotherapeutic applications. The notable findings in our present studies are (i) the remarkable cytotoxicity of the nanocomposite (1-AuNPs) to A549 (IC₅₀: 0.006 μM) and HaCaT (IC₅₀: 0.0075 μM) cells in red light (600-720 nm, 30 J/cm²) while almost nontoxic (IC₅₀ > 500 μg/mL, 0.053 μM) in the dark, (ii) the nontoxicity of 1-AuNPs to normal human diploid fibroblasts (WI-38) or human peripheral lung epithelial (HPL1D) cells (IC₅₀ > 500 μg/mL, 0.053 μM) both in the dark and red light signifying the target-specific anticancer activity of the nanocomposite, (iii) localization of 1-AuNPs in mitochondria and partly nucleus, (iv) remarkable red light-induced generation of reactive oxygen species (ROS: ¹O₂, ^•OH) in vitro, (v) disruption of the mitochondrial membrane due to enhanced oxidative stress, and (vi) caspase 3/7-dependent apoptosis. A similar cytotoxic profile of complex 1 was another key finding of our studies. Overall, our current investigations show a new red light-absorbing iron(III)-phenolate/carboxylate complex-functionalized gold nanocomposite (1-AuNPs) as the emerging next-generation iron-based photochemotherapeutic agent for targeted cancer treatment modality.

Photo-physical, theoretical and photo-cytotoxic evaluation of a new class of lanthanide(iii)–curcumin/diketone complexes for PDT application

Improved ISC in La(iii) complex of curcumin, on activation with visible light, has resulted in high yield of ¹O₂ in HeLa/MCF-7 cells, leading to the oxidative stress which was responsible for remarkable caspase 3/7-dependent apoptotic photocytotoxicity.