Antibacterial Photodynamic Therapy by Zn(II)-Curcumin Complex: Synthesis, Characterization, DFT Calculation, Antibacterial Activity, and Molecular Docking.

The increase in antibacterial drug resistance is threatening global health conditions. Recently, antibacterial photodynamic therapy (aPDT) has emerged as an effective antibacterial treatment with high cure gain. In this work, three Zn(II) complexes viz., [Zn(en)(acac)Cl] (1), [Zn(bpy)(acac)Cl] (2), [Zn(en)(cur)Cl] (3), where en=ethylenediamine (1 and 3), bpy=2,2'-bipyridine (2), acac=acetylacetonate (1 and 2), cur=curcumin monoanionic (3) were developed as aPDT agents. Complexes 1-3 were synthesized and fully characterized using NMR, HRMS, FTIR, UV-Vis. and fluorescence spectroscopy. The HOMO-LUMO energy gap (Eg), and adiabatic splittings (ΔS1-T1 and ΔS0-T1 ) obtained from DFT calculation indicated the photosensivity of the complexes. These complexes have not shown any potent antibacterial activity under dark conditions but the antibacterial activity of these complexes was significantly enhanced upon light exposure (MIC value up to 0.025 µg/mL) due to their light-mediated 1 O2 generation abilities. The molecular docking study suggested that complexes 1-3 interact efficiently with DNA gyrase B (PDB ID: 4uro). Importantly, 1-3 did not show any toxicity toward normal HEK-293 cells. Overall, in this work, we have demonstrated the promising potential of Zn(II) complexes as effective antibacterial agents under the influence of visible light.

Polypyridyl CoII -Curcumin Complexes as Photoactivated Anticancer and Antibacterial Agents.

Four new CoII complexes, [Co(bpy)2 (acac)]Cl (1), [Co(phen)2 (acac)]Cl (2), [Co(bpy)2 (cur)]Cl (3), [Co(phen)2 (cur)]Cl (4), where bpy=2,2'-bipyridine (1 and 3), phen=1,10-phenanthroline (2 and 4), acac=acetylacetonate (1 and 2), cur=curcumin monoanion (3 and 4) have been designed, synthesized and fully characterized. The X-ray crystal structures of 1 and 2 indicated that the CoN4 O2 core has a distorted octahedral geometry. The photoactivity of these complexes was tuned by varying the π conjugation in the ligands. Curcumin complexes 3 and 4 had an intense absorption band near 435 nm, which made them useful as visible-light photodynamic therapy agents; they also showed fluorescence with λem ≈565 nm. This fluorescence was useful for studying their intracellular uptake and localization in MCF-7 breast cancer cells. The acetylacetonate complexes (1 and 2) were used as control complexes to understand the role of curcumin. The white-light-triggered anticancer profiles of the cytosol targeting complexes 3 and 4 were investigated in detail. These non-dark toxic complexes displayed significant apoptotic photo-cytotoxicity (under visible light) against MCF-7 cells through ROS generation. The control complexes 1 and 2 did not induce significant cell death in the light or dark. Interestingly, 1-4 produced a remarkable antibacterial response upon light exposure. Overall, the reported results here can increase the boundary of the CoII -based anticancer and antibacterial drug development.

Biomedical engineering aspects of nanocellulose: a review.

Cellulose is one of the most abundant renewable biopolymer in nature and is present as major constituent in both plant cell walls as well as synthesized by some microorganisms as extracellular products. In both the systems, cellulose self-assembles into a hierarchical ordered architecture to form micro to nano-fibrillated structures, on basis of which it is classified into various forms. Nanocellulose (NCs) exist as rod-shaped highly crystalline cellulose nanocrystals to high aspect ratio cellulose nanofibers, micro-fibrillated cellulose and bacterial cellulose (BC), depending upon the origin, structural and morphological properties. Moreover, NCs have been processed into diversified products ranging from composite films, coatings, hydrogels, aerogels, xerogels, organogels, rheological modifiers, optically active birefringent colored films using traditional-to-advanced manufacturing techniques. With such versatility in structure-property, NCs have profound application in areas of healthcare, packaging, cosmetics, energy, food, electronics, bioremediation, and biomedicine with promising commercial potential. Herein this review, we highlight the recent advancements in synthesis, fabrication, processing of NCs, with strategic chemical modification routes to tailor its properties for targeted biomedical applications. We also study the basic mechanism and models for biosynthesis of cellulose in both plant and microbial systems and understand the structural insights of NC polymorphism. The kinetics study for both enzymatic/chemical modifications of NCs and microbial growth behavior of BC under various reactor configurations are studied. The challenges associated with the commercial aspects as well as industrial scale production of pristine and functionalized NCs to meet the growing demands of market are discussed and prospective strategies to mitigate them are described. Finally, post chemical modification evaluation of biological and inherent properties of NC are important to determine their efficacy for development of various products and technologies directed for biomedical applications.

Review on development of assigned value microbiological reference materials used in food testing.

Evolving testing methods in food Microbiology have resulted in the need for different types of microbiological reference materials. Based on the research articles available in this area, it is evident that development has been quite substantial in chemical testing compared to Microbiology. The primary reason could be the ease of spiking, and recovery in chemical RM as compared to microbiological RM. A significant challenge faced in recovery and stability during the development of quantitative microbiological RM depends on temperature, type of microbiological media used, method of analysis including reconstitution method, interference due to antimicrobial agents in food matrices, and competitor microorganisms present in higher numbers then the target microorganisms. Most of the research papers published on microbiological reference materials are contributed by developed economies were in the information related to complex food matrices are limited. Further analysis of different International Depository Agencies under the Budapest treaty indicates that there are only three institutes based in Europe providing quantitative or assigned value RM. This, in turn, highlights the scarcity in the availability of quantitative RM in Microbiology. This article provides a global overview of the availability of microbiological RM, microbial preservation techniques, protective agents, and elaboration on developing different formats of microbiological RM used in food testing.

Topochemical Synthesis of Ca3 CrN3 H Involving a Rotational Structural Transformation for Catalytic Ammonia Synthesis.

Topochemical reactions have led to great progress in the discovery of new metastable compounds with novel chemical and physical properties. With these reactions, the overall crystal structure of the host material is generally maintained. Here we report a topochemical synthesis of a hexagonal nitride hydride, h-Ca3 CrN3 H, by heating an orthorhombic nitride, o-Ca3 CrN3 , under hydrogen at 673 K, accompanied by a rotational structural transformation. The hydrogen intercalation modifies the Ca-N rock-salt-like atomic packing in o-Ca3 CrN3 to a face-sharing octahedral chain in h-Ca3 CrN3 H, mimicking a "hinged tessellation" movement. In addition, the h-Ca3 CrN3 H exhibited stable ammonia synthesis activity when used as a catalyst.

Ruthenium-Catalyzed Oxidative Homocoupling of Arylboronic Acids in Water: Ligand Tuned Reactivity and Mechanistic Study.

Molecular catalysts based on water-soluble arene-Ru(II) complexes ([Ru]-1-[Ru]-5) containing aniline (L1), 2-methylaniline (L2), 2,6-dimethylaniline (L3), 4-methylaniline (L4), and 4-chloroaniline (L5) were designed for the homocoupling of arylboronic acids in water. These complexes were fully characterized by (1)H, (13)C NMR, mass spectrometry, and elemental analyses. Structural geometry for two of the representative arene-Ru(II) complexes [Ru]-3 and [Ru]-4 was established by single-crystal X-ray diffraction studies. Our studies showed that the selectivity toward biaryls products is influenced by the position and the electronic behavior of various substituents of aniline ligand coordinated to ruthenium. Extensive investigations using (1)H NMR, (19)F NMR, and mass spectral studies provided insights into the mechanistic pathway of homocoupling of arylboronic acids, where the identification of important organometallic intermediates, such as σ-aryl/di(σ-aryl) coordinated arene-Ru(II) species, suggested that the reaction proceeds through the formation of crucial di(σ-aryl)-Ru intermediates by the interaction of arylboronic acid with Ru-catalyst to yield biaryl products.

Room-temperature chemoselective reduction of nitro groups using non-noble metal nanocatalysts in water.

Purely aqueous-phase chemoselective reduction of a wide range of aromatic and aliphatic nitro substrates has been performed in the presence of inexpensive Ni- and Co-based nanoparticle catalysts using hydrazine hydrate as a reducing agent at room temperature. Along with the observed high conversions and selectivities, the studied nanoparticle catalysts also exhibit a high tolerance to other highly reducible groups present in the nitro substrates. The development of these potential chemoselective reduction catalysts also provides a facile route for the synthesis of other industrially important fine chemicals or biologically important compounds, where other highly reducible groups are present in close proximity to the targeted nitro groups.

Direct vs. indirect pathway for nitrobenzene reduction reaction on a Ni catalyst surface: a density functional study.

Density functional theory (DFT) calculations are performed to understand and address the previous experimental results that showed the reduction of nitrobenzene to aniline prefers direct over indirect reaction pathways irrespective of the catalyst surface. Nitrobenzene to aniline conversion occurs via the hydroxyl amine intermediate (direct pathway) or via the azoxybenzene intermediate (indirect pathway). Through our computational study we calculated the spin polarized and dispersion corrected reaction energies and activation barriers corresponding to various reaction pathways for the reduction of nitrobenzene to aniline over a Ni catalyst surface. The adsorption behaviour of the substrate, nitrobenzene, on the catalyst surface was also considered and the energetically most preferable structural orientation was elucidated. Our study indicates that the parallel adsorption behaviour of the molecules over a catalyst surface is preferable over vertical adsorption behaviour. Based on the reaction energies and activation barrier of the various elementary steps involved in direct or indirect reaction pathways, we find that the direct reduction pathway of nitrobenzene over the Ni(111) catalyst surface is more favourable than the indirect reaction pathway.

Correlation of polymorphism in Toll-Like Receptor (TLR1 and TLR2) genes with susceptibility of pulmonary tuberculosis in Doda region of India.

BACKGROUND: Pulmonary tuberculosis has emerged as one of the leading causes of deaths across the globe. The prevalence of Mycobacterium tuberculosis has also shown an increasing trend over the time which may be attributed to the increase in multidrug resistant strains and HIV epidemics. There are several factors like change in the gene structure and cellular activities of the host and the bacterium which may have changed the host response towards tuberculosis. Additionally, the recent reports have suggested that Toll-Like Receptors (TLRs) play an important role in the activation of immune responses against various pathogens. Therefore, this study has been designed to investigate the possible correlation of TLR gene polymorphism and prevalence of pulmonary tuberculosis. METHOD: This study investigates 300 samples collected from patients with pulmonary tuberculosis (150) and healthy controls (150) from the Doda region of Jammu, India. For analysis purpose, DNA from the collected samples were isolated and subjected to sequence specific PCR amplification of TLR-1 and TLR-2 genes. The amplicons of TLR-1 and TLR-2 were further digested with restriction enzymes PvuII and Xbal, respectively, and visualized on agarose gel, subsequently. RESULT: The results suggest that frequency of TLR2 gene polymorphism (73.9%) is high in the patients below the age of 50 years, whereas, frequency of TLR-1 gene polymorphism is high (71%) in the patients above 50 years of age (p = 0.005). Further, the restriction digestion analysis of TLR1 genes has shown that nearly 78% of the confirmed normal cases exhibit homozygous normal conditions followed by 12% cases with heterozygous conditions and 10% cases of homozygous mutants. Similarly for TLR2 genes, nearly 78.6% of the confirmed normal cases have shown homozygous normal conditions followed heterozygous conditions (12.6%) and homozygous mutants (8.6%). CONCLUSION: This study establishes a preliminary correlation between TLR polymorphism and tuberculosis.

Microplastic and adhesive free, multifunctional, circular economy approach-based biomass-derived drinking straws.

Generation of voluminous single-use plastic waste and byproducts from agricultural harvests such as rice straws (RSs) are major global challenges due to their disposal issues, contributing to greenhouse gas emissions, and affecting the ecological system with threats to human health. A scalable, low-cost, and eco-friendly strategy for fabricating cellulose-silica-based drinking straws, free from microplastics and adhesive, through strategic valorization of RS is reported. Functionalization by delignification-cum-crosslinking of RS leads to development of straws with high water stability (∼5 days), solvothermal stability (0°C-95°C), tensile strength (128 MPa), low migration values (<60 mg/kg), improved biodegradability (∼126 days) with reduced wettability and hydrophobicity. RS drinking straws show antibacterial, self-cleaning, self-healing, anti-fizzing, reusable, and generate significantly lower carbon footprint (<99.8% and <53.34% global warming potential than metal and polylactic acid straws). Repurposing of agro-wastes from farms to commercially viable drinking straws which biodegrades after its consumption achieves the goal of circular economy and sustainable development.

Vitamin B6 appended polypyridyl Co(III) complexes for photo-triggered antibacterial activity.

Three novel polypyridyl-Co(III)-vitamin B6 complexes viz., [Co(CF3-phtpy)(SBVB6)]Cl (Co1), [Co(anthracene-tpy)(SBVB6)]Cl (Co2), [Co(NMe2-phtpy)(SBVB6)]Cl (Co3), where 4'-(4-(trifluoromethyl)phenyl)-2,2':6',2''-terpyridine = CF3-phtpy, 4'-(anthracen-9-yl)-2,2':6',2''-terpyridine = anthracene-tpy;, 4-([2,2':6',2''-terpyridin]-4'-yl)-N,N-dimethylaniline = NMe2-phtpy, (E)-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylpyridin-3-ol = H2SBVB6 was successfully developed for aPDT (antibacterial photodynamic therapy) applications. Co1-Co3 exhibited an intense absorption band at ca. 435-485 nm, which is attributed to ligand-to-metal charge transfer and was beneficial for antibacterial photodynamic therapy. The distorted octahedral geometry of the complexes with CoIIIN4O2 core was evident from the DFT study. The visible light absorption ability and good photo-stability of Co1-Co3 made them good photosensitizers for aPDT. Co1-Co3 displayed significant antibacterial responses against gram-positive (S. aureus) and gram-negative (E. coli) bacteria upon light exposure (10 J cm-2, 400-700 nm) and showed MIC values between 0.01-0.005 µg mL-1. The aPDT activities of these complexes were due to their ability to damage bacterial cell membranes via ROS generation. Overall, this study shows the photo-triggered ROS-mediated bacteria-killing potential of Co(III) complexes.

Scalable phosphorylated cellulose production with improved environmental sustainability, crosslinkability and processability using 3D bioprinting for dye remediation.

In the present work, phosphorylated cellulose (PC) gel has been produced following an environmentally benign approach using agro-based chemicals with improved yield. The PC gels produced were transparent, negatively charged with high consistency, charge content (1133.33 mmol/kg), degree of substitution (DS) of 0.183 and increased yield (>87 %). The XPS and EDS analysis confirms the covalently bonded phosphate groups at weight percent of 9.42 % and 11.01 %, respectively. The life cycle assessment (LCA) shows that PC gel production via the phosphorylation route is an ecologically favourable strategy compared with traditional TEMPO oxidation, resulting in 1.67 times lower CO2 emission. The rheological studies of PC gels show shear-thinning behaviour with improved 3D printability followed by heat-induced crosslinking of phosphate groups. The mechanistic insights for the condensation of phosphate to form a phosphoric ester group during cross-linking were evaluated through 31P solid-state NMR and XPS studies. Interestingly, the 3D-printed structures showed high structural stability under both compression and tensile load in both dry and wet conditions, with high water absorption (5408.33 %) and swelling capacity of 700 %. The structures show improved methylene blue (MB) remediation capabilities with a maximum removal efficiency of 99 % for 10-200 mg/L and more than seven times reusability. This work provides a green, facile and energy-efficient strategy for fabricating PCs with easy processability through additive manufacturing techniques for producing value-added products, opening up new avenues for high-performance applications.

Biochemical unravelling of the endoxylanase activity in a bifunctional GH39 enzyme cloned and expressed from thermophilic Geobacillus sp. WSUCF1.

The glycoside hydrolase family 39 (GH39) proteins are renowned for their extremophilic and multifunctional enzymatic properties, yet the molecular mechanisms underpinning these unique characteristics continue to be an active subject of research. In this study, we introduce WsuXyn, a GH39 protein with a molecular weight of 58 kDa, originating from the thermophilic Geobacillus sp. WSUCF1. Previously reported for its exceptional thermostable ß-xylosidase activity, WsuXyn has recently demonstrated a significant endoxylanase activity (3752 U·mg-1) against beechwood xylan, indicating towards its bifunctional nature. Physicochemical characterization revealed that WsuXyn exhibits optimal endoxylanase activity at 70 °C and pH 7.0. Thermal stability assessments revealed that the enzyme is resilient to elevated temperatures, with a half-life of 168 h. Key kinetic parameters highlight the exceptional catalytic efficiency and strong affinity of the protein for xylan substrate. Moreover, WsuXyn-mediated hydrolysis of beechwood xylan has achieved 77 % xylan conversion, with xylose as the primary product. Structural analysis, amalgamated with docking simulations, has revealed strong binding forces between xylotetraose and the protein, with key amino acid residues, including Glu278, Tyr230, Glu160, Gly202, Cys201, Glu324, and Tyr283, playing pivotal roles in these interactions. Therefore, WsuXyn holds a strong promise for biodegradation and value-added product generation through lignocellulosic biomass conversion.

Valorization of sugarcane bagasse with in situ grown MoS2 for continuous pollutant remediation and microbial decontamination.

In this study, sugarcane bagasse (SB) was strategically subjected to a delignification process followed by the in situ growth of multi-layered molybdenum disulfide (MoS2) nanosheets with hexagonal phase (2H-phase) crystal structure via hydrothermal treatment. The MoS2 nanosheets underwent self-assembly to form nanoflower-like structures in the aligned cellulose inter-channels of delignified sugarcane bagasse (DSB), the mechanism of which was understood through FTIR and XPS spectroscopic studies. DSB, due to its porous morphology and abundant hydroxyl groups, shows remediation capabilities of methylene blue (MB) dye through physio-sorption but shows a low adsorption capacity of 80.21 mg/g. To improve the removal capacity, DSB after in situ growth of MoS2 (DSB-MoS2) shows enhanced dye degradation to 114.3 mg/g (in the dark) which further improved to 158.74 mg/g during photodegradation, due to catalytically active MoS2. Interestingly, DSB-MoS2 was capable of continuous dye degradation with recyclability for three cycles, reaching an efficiency of > 83%, along with a strong antibacterial response against Gram-positive Staphylococcus aureus (S.aureus) and Gram-negative Escherichia coli (E. coli). The present study introduces a unique strategy for the up-conversion of agricultural biomass into value-added bio-adsorbents, which can effectively and economically address the remediation of dyes with simultaneous microbial decontamination from polluted wastewater streams.

Rice husk valorisation by in situ grown MoS2 nanoflowers: a dual-action catalyst for pollutant dye remediation and microbial decontamination.

Rice husk (RH) is a common agricultural waste generated during the rice milling process; however, a major portion is either burned or disposed of in landfills, posing significant environmental risks. In this study, RH waste was transformed into bio-based catalysts via delignification cum in situ growth of MoS2 (DRH-MoS2) for efficient pollutant dye removal and microbial decontamination. The developed DRH-MoS2 exhibits nanoflower-like structures with a 2H-MoS2 phase and a narrow band gap of 1.37 eV, which showed strong evidence of photocatalytic activity. With the presence of abundant hydroxyl functionality, delignified rice husk (DRH) exhibits a malachite green (MG) dye adsorption capacity of 88 mg g-1. However, in situ growth of MoS2 nanosheets on DRH enhances MG degradation to 181 mg g-1 under dark conditions and 550 mg g-1 in the presence of light. Mechanistic insights reveal a synergistic adsorption-cum-degradation phenomenon, amplified by generation of reactive oxygen species during photodegradation which was confirmed from radical scavenging activity. Interestingly, DRH-MoS2 demonstrates potent antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) with sustained photodegradation efficiency (>80%) over three cycles. The present work reports a cost-effective and scalable strategy for environmental remediation of real wastewater which usually contains both dye pollutants as well as microbes using abundantly available renewable resources such as sunlight and agricultural biomass wastes.

Silicon Clathrate-Supported Catalysts with Low Work Functions for Ammonia Synthesis.

Diamond-type silicon has a work function of ≈4.8 eV, and conventional n- or p-type doping modifies the value only between 4.6 and 5.05 eV. Here, it is shown that the alkali clathrates AxSi46 have substantially lower work functions approaching 2.6 eV, with clear trends between alkali electropositivity and clathrate cage size. The low work function enables alkali clathrates such as K8Si46 to be effective Haber-Bosch catalyst supports for NH3 synthesis. The catalytic properties of Si, Ge, and Sn-based clathrates are investigated while supporting Fe and Ru on the surface. The activity largely scales with the work function, and low activation energies below 60 kJ mol-1 are observed due to strong electron donation effects from the support. Ru metal and Sn clathrates seem to be unsuitable for stability issues. Compared to other similar hydride/electride catalysts, the simple structure and composition combined with stability in air/water make a systematic study of these clathrates possible and open the door to other electron-rich Zintl phases and related intermetallics as low-work function materials suitable for catalysis. The observed low work function may also have implications for other existing electronic applications.

Survival of Salmonella spp. and Pathogenic Escherichia coli in Food Matrixes and Its Relevance in the Development of Proficiency Testing Samples.

Monitoring of food products by government agencies for their compliance to regulatory limits is an essential step in controlling foodborne outbreaks. For monitoring purposes, an extensive setup of the surveillance system is used, which involves ISO 17025:2017 accredited laboratories for food testing. Participation in proficiency testing (PT) programs is a requirement of ISO 17025:2017, which ensures data accuracy and analyst competency. Participation in PT schemes is costly for laboratories in developing countries as most of the commercial suppliers are situated in the United States and Europe. The literature or data available on creation of microbiological proficiency testing is scanty as much of the data available with commercial suppliers are trade secrets, and there is only 0.06% of research articles available in the Scopus database on the topic. In this review article, an attempt is made to understand the factors impacting the survival of two important foodborne pathogens, i.e., Escherichia coli and Salmonella spp., by extracting information available from growth studies and root-cause analysis of various food safety incidents and recalls. Utilization of this information in the development of PT samples is discussed in this review article along with a focus on the availability of PT samples and associated ISO standards to formulate homogeneous and stable PT samples. This review article elaborates on the focus areas that can be considered by PT providers (PTP)-for example, initial inoculum level and preparation, strain type, microbial growth phase, the impact of different types of food matrixes including low-moisture food, antimicrobial components, pH, presence of competitor microbes, and environmental conditions involving storage temperature, time, and relative humidity. These focus areas can be used to successfully create PT samples by PTP in developing countries.

Superporous soy protein isolate matrices as superabsorbent dressings for successful management of highly exuding wounds: In vitro and in vivo characterization.

Soy protein isolate (SPI) has received widespread attention of the biomedical research community primarily due to its good biocompatibility, biodegradability, high availability and low cost. Herein, glutaraldehyde cross-linked microporous sponge-like SPI scaffolds were prepared using the cryogelation technique for tissue engineering applications. The prepared SPI scaffolds possess an interconnected porous structure with approximately 90% porosity and an average pore size in the range of 45-92 µm. The morphology, porosity, swelling capacity and degradation rate of the cryogels were found to be dependent on the concentration of polymer to crosslinking agent. All cryogels were found to be elastic and able to maintain physical integrity even after being compressed to one-fifth of their original length during cyclic compression analysis. These cryogels showed excellent mechanical properties, immediate water-triggered shape restoration and absorption speed. Furthermore, cryogels outperformed cotton and gauze in terms of blood clotting and blood cell adherence. The in vitro and in vivo studies demonstrated the potency of SPI scaffolds for skin tissue engineering applications. Our findings showed that crosslinking with glutaraldehyde had no detrimental effects on cell viability. In addition, an in vivo wound healing study in rats validated them as good potential wound dressing materials.

Ammonia Synthesis via an Associative Mechanism on Alkaline Earth Metal Sites of Ca3 CrN3 H.

Typically, transition metals are considered as the centers for the activation of dinitrogen. Here we demonstrate that the nitride hydride compound Ca3 CrN3 H, with robust ammonia synthesis activity, can activate dinitrogen through active sites where calcium provides the primary coordination environment. DFT calculations also reveal that an associative mechanism is favorable, distinct from the dissociative mechanism found in traditional Ru or Fe catalysts. This work shows the potential of alkaline earth metal hydride catalysts and other related 1 D hydride/electrides for ammonia synthesis.

Polypyridyl-based Co(III) complexes of vitamin B6 Schiff base for photoactivated antibacterial therapy.

Herein, five novel polypyridyl-based Co(III) complexes of Schiff bases, viz., [Co(dpa)(L1)]Cl (1), [Co(dpa)(L2)]Cl (2), [Co(L3)(L2)]Cl (3), [Co(L3)(L1)]Cl (4), and [Co(L4)(L1)]Cl (5), where dpa (dipicolylamine) = bis(2-pyridylmethyl)amine; H2L1 = (E)-2-((2-hydroxybenzylidene)amino)phenol; H2L2 = (E)-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylpyridin-3-ol; L3 = 4'-phenyl-2,2':6',2''-terpyridine (ph-tpy); and L4 = 4'-ferrocenyl-2,2':6',2''-terpyridine (Fc-tpy), were synthesized and characterized. Complexes 1, 3, and 4 were structurally characterized by single-crystal XRD, indicating an octahedral CoIIIN4O2 coordination core. The absorption bands of these complexes were observed in the visible range with a λmax at ∼430-485 nm. Complex 5 displayed an extra absorption band near 545 nm because of a ferrocene moiety. These absorptions in the visible region reflect the potential of the complexes to act as visible-light antimicrobial photodynamic therapy (aPDT) agents. All of these complexes showed reactive oxygen species (ROS)-mediated antibacterial effects against S. aureus (Gram-positive) and E. coli (Gram-negative bacteria) upon low-energy visible light (0.5 J cm-2, 400-700 nm) exposure. Additionally, 1-5 did not show any toxicity toward A549 (Human Lung adenocarcinoma) cells, reflecting their selective bacteria-killing abilities.