Fabrication of silicon-based nickel nanoflower-encapsulated gelatin microspheres as an active antimicrobial carrier.

Local antibiotic application might mitigate the burgeoning problem of rapid emergence of antibiotic resistance in pathogenic microbes. To accomplish this, delivery systems must be engineered. Hydrogels have a wide range of physicochemical properties and can mimic the extracellular matrix, rendering them promising materials for local antibacterial agent application. Here, we synthesized antibacterial silicon (Si)-based nickel (Ni) nanoflowers (Si@Ni) and encapsulated them in gelatin methacryloyl (GelMA) using microfluidic and photo-crosslink technology, constructing uniform micro-sized hydrogel spheres (Si@Ni-GelMA). Si@Ni and Si@Ni-GelMA were characterized using X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Injectable Si@Ni-GelMA exhibited excellent antibacterial activities owing to the antibiotic effect of Ni against Pseudomonas aeruginosa, Klebsiella pneumoniae, and methicillin-resistant Staphylococcus aureus, while showing negligible cytotoxicity. Therefore, the Si@Ni-GelMA system can be used as drug carriers owing to their injectability, visible light-mediated crosslinking, degradation, biosafety, and superior antibacterial properties.

Recent advances in nanoflowers: compositional and structural diversification for potential applications.

In recent years, nanoscience and nanotechnology have emerged as promising fields in materials science. Spectroscopic techniques like scanning tunneling microscopy and atomic force microscopy have revolutionized the characterization, manipulation, and size control of nanomaterials, enabling the creation of diverse materials such as fullerenes, graphene, nanotubes, nanofibers, nanorods, nanowires, nanoparticles, nanocones, and nanosheets. Among these nanomaterials, there has been considerable interest in flower-shaped hierarchical 3D nanostructures, known as nanoflowers. These structures offer advantages like a higher surface-to-volume ratio compared to spherical nanoparticles, cost-effectiveness, and environmentally friendly preparation methods. Researchers have explored various applications of 3D nanostructures with unique morphologies derived from different nanoflowers. The nanoflowers are classified as organic, inorganic and hybrid, and the hybrids are a combination thereof, and most research studies of the nanoflowers have been focused on biomedical applications. Intriguingly, among them, inorganic nanoflowers have been studied extensively in various areas, such as electro, photo, and chemical catalysis, sensors, supercapacitors, and batteries, owing to their high catalytic efficiency and optical characteristics, which arise from their composition, crystal structure, and local surface plasmon resonance (LSPR). Despite the significant interest in inorganic nanoflowers, comprehensive reviews on this topic have been scarce until now. This is the first review focusing on inorganic nanoflowers for applications in electro, photo, and chemical catalysts, sensors, supercapacitors, and batteries. Since the early 2000s, more than 350 papers have been published on this topic with many ongoing research projects. This review categorizes the reported inorganic nanoflowers into four groups based on their composition and structure: metal, metal oxide, alloy, and other nanoflowers, including silica, metal-metal oxide, core-shell, doped, coated, nitride, sulfide, phosphide, selenide, and telluride nanoflowers. The review thoroughly discusses the preparation methods, conditions for morphology and size control, mechanisms, characteristics, and potential applications of these nanoflowers, aiming to facilitate future research and promote highly effective and synergistic applications in various fields.

Construction of a bioactive copper-based metal organic framework-embedded dual-crosslinked alginate hydrogel for antimicrobial applications.

Metal-organic frameworks (MOFs) containing bioactive metals have the potential to exhibit antimicrobial activity by releasing metal ions or ligands through the cleavage of metal-ligand bonds. Recently, copper-based MOFs (Cu-MOFs) with sustained release capability, porosity, and structural flexibility have shown promising antimicrobial properties. However, for clinical use, the controlled release of Cu2+ over an extended time period is crucial to prevent toxicity. In this study, we developed an alginate-based antimicrobial scaffold and encapsulated MOFs within a dual-crosslinked alginate polymer network. We synthesized Cu-MOFs containing glutarate (Glu) and 4,4'-azopyridine (AZPY) (Cu(AZPY)-MOF) and encapsulated them in an alginate-based hydrogel through a combination of visible light-induced photo and calcium ion-induced chemical crosslinking processes. We confirmed Cu(AZPY)-MOF synthesis using scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, and thermogravimetric analysis. This antimicrobial hydrogel demonstrated excellent antibacterial and antifungal properties against two bacterial strains (MRSA and S. mutans, with >99.9 % antibacterial rate) and one fungal strain (C. albicans, with >78.7 % antifungal rate) as well as negligible cytotoxicity towards mouse embryonic fibroblasts, making it a promising candidate for various tissue engineering applications in biomedical fields.

Rod-to-sphere elemental reconstruction of biocompatible Ag2Te-Ag4.53-Te3 nanoparticles for triple negative breast cancer photo-nano-therapy.

Silver nanoparticles (AgNPs) continue to be applied to agricultural and medical applications because of their antibacterial and antifungal effects. However, AgNPs are vulnerable to poisoning by oxidation or sulfidation, and unintentional toxicity can occur via leaching. Therefore, ensuring the stability of AgNPs for practical applications is considered an important requirement. In this study, we propose the solvothermal galvanic replacement of a Te nanorod (TeNR) template with a Ag precursor to manufacture highly stable and biocompatible Ag-Te nanoparticles (AgTeNPs). In addition to their high stability, AgTeNPs composed of Ag2Te-Ag4.53Te3 were evaluated as a nanotherapeutic agent enabled by their selective toxicity through metabolic degradation in breast cancer cells. It has been demonstrated that combinatorial treatment with hyperthermic cancer-cell ablation through photothermal conversion provides an effective cancer treatment in vitro and in vivo. The discovered new biocompatible Ag nanomaterials with innate anticancer effects are expected to be applied to various application fields.

Highly Sensitive Interdigitated Capacitive Humidity Sensors Based on Sponge-Like Nanoporous PVDF/LiCl Composite for Real-Time Monitoring.

In this study, a sponge-like poly(vinylidene fluoride) (PVDF)/lithium chloride (LiCl) nanocomposite-entrenched interdigitated capacitive (IDC) sensor was developed for real-time humidity-sensing applications. Here, we demonstrated a sponge-like nanoporous structure ranging from 200 nm to 2 µm size holes, the PVDF/LiCl structure fabricated on an interdigitated capacitor (IDC) electrode functioning as a high-performance sensor because of the presence of ionized LiCl. The nanoporous PVDF/LiCl composite-based humidity sensor exhibited a high sensitivity of 12.6 nF/% relative humidity (RH), a linearity of 0.990, and a low hysteresis of 2.6% in the range of 25-95% RH. The composite film exhibited a response time of 17.7 s, a recovery time of 21 s, and an intensified increase of 8.02 nF/s (a decrease of 6.7 nF/s). The sensor designed demonstrates ultra-high sensing characteristics with 10 times higher sensitivity, i.e., 12.678.96 pF/%RH as compared to other polymer-based composite humidity sensors. Owing to the sensing performance and portability, the proposed nanoporous PVDF/LiCl composite-based IDC sensor is expected to be a promising platform for a wide range of humidity-sensing applications, including real-time breath monitoring and non-contact sensing.

Inorganic Nanoflowers-Synthetic Strategies and Physicochemical Properties for Biomedical Applications: A Review.

Nanoflowers, which are flower-shaped nanomaterials, have attracted significant attention from scientists due to their unique morphologies, facile synthetic methods, and physicochemical properties such as a high surface-to-volume ratio, enhanced charge transfer and carrier immobility, and an increased surface reaction efficiency. Nanoflowers can be synthesized using inorganic or organic materials, or a combination of both (called a hybrid), and are mainly used for biomedical applications. Thus far, researchers have focused on hybrid nanoflowers and only a few studies on inorganic nanoflowers have been reported. For the first time in the literature, we have consolidated all the reports on the biomedical applications of inorganic nanoflowers in this review. Herein, we review some important inorganic nanoflowers, which have applications in antibacterial treatment, wound healing, combinatorial cancer therapy, drug delivery, and biosensors to detect diseased conditions such as diabetes, amyloidosis, and hydrogen peroxide poisoning. In addition, we discuss the recent advances in their biomedical applications and preparation methods. Finally, we provide a perspective on the current trends and potential future directions in nanoflower research. The development of inorganic nanoflowers for biomedical applications has been limited to date. Therefore, a diverse range of nanoflowers comprising inorganic elements and materials with composite structures must be synthesized using ecofriendly synthetic strategies.

Therapeutic Potency of NO Loaded into Anticancer Copper Metal-Organic Framework through Nonclassical Hydrogen Bonding.

Metal-organic frameworks (MOFs) are potential exogenous scaffolds for therapeutic nitric oxide (NO) delivery because they can store drug or bioactive gas molecules within pores or on active metal sites. Herein, we employed a Cu-MOF coordinated with glutarate (glu) and 1,2-bis(4-pyridyl)ethane (bpa) to obtain NO-loaded Cu-MOF (NO⊂Cu-MOF). NO loading transformed the space group of Cu-MOF from monoclinic C2/c to triclinic P-1 through nonclassical hydrogen bonding with glu and bpa. Cu-MOF showed good stability in deionized water and phosphate-buffered saline. NO⊂Cu-MOF released up to 1.10 µmol mg-1 NO over 14.6 h at 37 °C, which is suitable for therapeutic applications. NO⊂Cu-MOF showed moderate biocompatibility with L-929 cells and significant anticancer activity against HeLa cells, suggesting an apoptosis-mediated cell death mechanism. These insights into NO bonding modes with Cu-MOF that enable controlled NO release can inspire the design of functional MOFs as hybrid NO donors for drug delivery.

Controllable Nitric Oxide Storage and Release in Cu-BTC: Crystallographic Insights and Bioactivity.

Crystalline metal-organic frameworks (MOFs) are extensively used in areas such as gas storage and small-molecule drug delivery. Although Cu-BTC (1, MOF-199, BTC: benzene-1,3,5-tricarboxylate) has versatile applications, its NO storage and release characteristics are not amenable to therapeutic usage. In this work, micro-sized Cu-BTC was prepared solvothermally and then processed by ball-milling to prepare nano-sized Cu-BTC (2). The NO storage and release properties of the micro- and nano-sized Cu-BTC MOFs were morphology dependent. Control of the hydration degree and morphology of the NO delivery vehicle improved the NO release characteristics significantly. In particular, the nano-sized NO-loaded Cu-BTC (NO⊂nano-Cu-BTC, 4) released NO at 1.81 µmol·mg-1 in 1.2 h in PBS, which meets the requirements for clinical usage. The solid-state structural formula of NO⊂Cu-BTC was successfully determined to be [CuC6H2O5]·(NO)0.167 through single-crystal X-ray diffraction, suggesting no structural changes in Cu-BTC upon the intercalation of 0.167 equivalents of NO within the pores of Cu-BTC after NO loading. The structure of Cu-BTC was also stably maintained after NO release. NO⊂Cu-BTC exhibited significant antibacterial activity against six bacterial strains, including Gram-negative and positive bacteria. NO⊂Cu-BTC could be utilized as a hybrid NO donor to explore the synergistic effects of the known antibacterial properties of Cu-BTC.

Injectable hyaluronic acid hydrogel encapsulated with Si-based NiO nanoflower by visible light cross-linking: Its antibacterial applications.

Bacterial infections have become a severe threat to human health and antibiotics have been developed to treat them. However, extensive use of antibiotics has led to multidrug-resistant bacteria and reduction of their therapeutic effects. An efficient solution may be localized application of antibiotics using a drug delivery system. For clinical application, they need to be biodegradable and should offer a prolonged antibacterial effect. In this study, a new injectable and visible-light-crosslinked hyaluronic acid (HA) hydrogel loaded with silicon (Si)-based nickel oxide (NiO) nanoflowers (Si@NiO) as an antibacterial scaffold was developed. Si@NiO nanoflowers were synthesized using chemical bath deposition before encapsulating them in the HA hydrogel under a mild visible-light-crosslinking conditions to generate a Si@NiO-hydrogel. Si@NiO synthesis was confirmed using scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. As-prepared Si@NiO-hydrogel exhibited enhanced mechanical properties compared to a control bare hydrogel sample. Moreover, Si@NiO-hydrogel exhibits excellent antibacterial properties against three bacterial strains (P. aeruginosa, K. pneumoniae, and methicillin-resistant Staphylococcus aureus (>99.9% bactericidal rate)) and negligible cytotoxicity toward mouse embryonic fibroblasts. Therefore, Si@NiO-hydrogel has the potential for use in tissue engineering and biomedical applications owing to its injectability, visible-light crosslink ability, degradability, biosafety, and superior antibacterial property.

Biocompatible Core-Shell-Structured Si-Based NiO Nanoflowers and Their Anticancer Activity.

Compared to most of nano-sized particles, core-shell-structured nanoflowers have received great attention as bioactive materials because of their high surface area with the flower-like structures. In this study, core-shell-structured Si-based NiO nanoflowers, Si@NiO, were prepared by a modified chemical bath deposition method followed by thermal reduction. The crystal morphology and basic structure of the composites were characterized by powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (BET) and porosity analysis (BJT), and inductively coupled plasma optical emission spectrometry (ICP-OES). The electrochemical properties of the Si@NiO nanoflowers were examined through the redox reaction of ascorbic acid with the metal ions present on the surface of the core-shell nanoflowers. This reaction favored the formation of reactive oxygen species. The Si@NiO nanoflowers showed excellent anticancer activity and low cytotoxicity toward the human breast cancer cell line (MCF-7) and mouse embryonic fibroblasts (MEFs), respectively, demonstrating that the anticancer activities of the Si@NiO nanoflowers were primarily derived from the oxidative capacity of the metal ions on the surface, rather than from the released metal ions. Thus, this proves that Si-based NiO nanoflowers can act as a promising candidate for therapeutic applications.

Therapeutic Application of Metal-Organic Frameworks Composed of Copper, Cobalt, and Zinc: Their Anticancer Activity and Mechanism.

Effective penetration into cells, or binding to cell membranes is an essential property of an effective nanoparticle drug delivery system (DDS). Nanoparticles are generally internalized through active transport mechanisms such as apoptosis, and cargo can be released directly into the cytoplasm. A metal-organic framework (MOF) is a network structure consisting of metal clusters connected by organic linkers with high porosity; MOFs provide a desirable combination of structural features that can be adjusted with large cargo payloads, along with Cu, Co, and Zn-MOFs, which have the chemical stability required for water-soluble use. Bioactive MOFs containing copper, cobalt, and zinc were prepared by modifying previous methods as therapeutic drugs. Their structures were characterized via PXRD, single-crystal crystallographic analysis, and FT-IR. The degradability of MOFs was measured in media such as deionized water or DPBS by PXRD, SEM, and ICP-MS. Furthermore, we investigated the anticancer activity of MOFs against the cell lines SKOV3, U87MG, and LN229, as well as their biocompatibility with normal fibroblast cells. The results show that a nanoporous 3D Cu-MOF could potentially be a promising candidate for chemoprevention and chemotherapy.

Polyurethane Foam Incorporated with Nanosized Copper-Based Metal-Organic Framework: Its Antibacterial Properties and Biocompatibility.

Polyurethane foams (PUFs) have attracted attention as biomaterials because of their low adhesion to the wound area and suitability as biodegradable or bioactive materials. The composition of the building blocks for PUFs can be controlled with additives, which provide excellent anti-drug resistance and biocompatibility. Herein, nanosized Cu-BTC (copper(II)-benzene-1,3,5-tricarboxylate) was incorporated into a PUF via the crosslinking reaction of castor oil and chitosan with toluene-2,4-diisocyanate, to enhance therapeutic efficiency through the modification of the surface of PUF. The physical and thermal properties of the nanosized Cu-BTC-incorporated PUF (PUF@Cu-BTC), e.g., swelling ratio, phase transition, thermal gravity loss, and cell morphology, were compared with those of the control PUF. The bactericidal activities of PUF@Cu-BTC and control PUF were evaluated against Pseudomonas aeruginosa, Klebsiella pneumoniae, and methicillin-resistant Staphylococcus aureus. PUF@Cu-BTC exhibited selective and significant antibacterial activity toward the tested bacteria and lower cytotoxicity for mouse embryonic fibroblasts compared with the control PUF at a dose of 2 mg mL-1. The Cu(II) ions release test showed that PUF@Cu-BTC was stable in phosphate buffered saline (PBS) for 24 h. The selective bactericidal activity and low cytotoxicity of PUF@Cu-BTC ensure it is a candidate for therapeutic applications for the drug delivery, treatment of skin disease, and wound healing.

Robust Copper Metal-Organic Framework-Embedded Polysiloxanes for Biomedical Applications: Its Antibacterial Effects on MRSA and In Vitro Cytotoxicity.

Polysiloxanes (PSs) have been widely utilized in the industry as lubricants, varnishes, paints, release agents, adhesives, and insulators. In addition, their applications have been expanded to include the development of new biomedical materials. To modify PS for application in therapeutic purposes, a flexible antibacterial Cu-MOF (metal-organic framework) consisting of glutarate and 1,2-bis(4-pyridyl)ethane ligands was embedded in PS via a hydrosilylation reaction of vinyl-terminated and H-terminated PSs at 25 °C. The bactericidal activities of the resulting Cu-MOF-embedded PS (PS@Cu-MOF) and the control polymer (PS) were tested against Escherichia coli, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus. PS@Cu-MOF exhibited more than 80% bactericidal activity toward the tested bacteria at a concentration of 100 µg⋅mL-1 and exhibited a negligible cytotoxicity toward mouse embryonic fibroblasts at the same concentration. Release tests of the Cu(II) ion showed PS@Cu-MOF to be particularly stable in a phosphate-buffered saline solution. Furthermore, its physical and thermal properties, including the phase transition, rheological measurements, swelling ratio, and thermogravimetric profile loss, were similar to those of the control polymer. Moreover, the low cytotoxicity and bactericidal activities of PS@Cu-MOF render it a promising candidate for use in medicinal applications, such as in implants, skin-disease treatment, wound healing, and drug delivery.

Novel Metal-Organic Framework-Based Photocrosslinked Hydrogel System for Efficient Antibacterial Applications.

Metal-organic frameworks (MOFs) can be applied in biology and medicine as drug delivery systems by carrying drugs on their surfaces or releasing bioactive ligands. To investigate the therapeutic potential of hydrogels that contain MOFs, three MOFs containing glutarate and 1,2-bis(4-pyridyl)ethylene ligands were synthesized by the previously reported hydrothermal or solvothermal reactions: Cu-MOF 1, Co-MOF 2, and Zn-MOF 3. Bioactive MOF-embedded hydrogels (hydrogel@Cu-MOF 1, hydrogel@Co-MOF 2, and hydrogel@Zn-MOF 3) were prepared by UV light-mediated thiol-ene photopolymerization using diacrylated polyethylene glycol (PEG), 4-arm-thiolated PEG, and MOFs. The activities of the MOF-embedded hydrogels were tested against the Gram-negative bacterium Escherichia coli and the Gram-positive bacterium Staphylococcus aureus. These MOF-embedded hydrogels were observed to be very stable, based on the release test of MII ions, and both hydrogel@Cu-MOF 1 and hydrogel@Co-MOF 2 showed excellent antibacterial activity. Although, in human dermal fibroblasts, hydrogel@Cu-MOF 1 showed no cytotoxic effects, it exhibited 99.9% antibacterial effects at the minimum bactericidal concentration. Physical properties such as the surface area and dimension of MOFs with different central metals appeared to be more important than the chemical properties of the ligands in determining the effects on bacteria. These MOF-embedded hydrogels may be useful in antibacterial applications such as cosmetics, treatment of skin diseases, and drug delivery owing to their low cytotoxicity and high bactericidal activity.

Antibacterial activities of Cu-MOFs containing glutarates and bipyridyl ligands.

Metal-organic frameworks (MOFs) can be utilized as antibacterial agents due to their effective antibacterial activities. Four three-dimensional (3D) Cu-MOFs formulated as [Cu2(Glu)2(µ-L)]·x(H2O) (Glu is glutarate, and L is bpy = 4,4'-bipyridine (1), bpa = 1,2-bis(4-pyridyl)ethane (2), bpe = 1,2-bis(4-pyridyl)ethylene (3), and bpp = 1,2-bis(4-pyridyl)propane (4)) were synthesized by hydrothermal reactions or modified literature methods. Their solid-state structures were slightly modified to increase their hydrolytic stabilities in aqueous solution. Despite the seemingly sufficient void spaces in all the solvent-free MOFs, only the thermally activated form of MOF 2 displayed selective gas uptake ability for CO2 over N2 and H2. The antibacterial activities of the four Cu-MOFs, 1, 2, 3, and 4, were investigated by determining their minimal bactericidal concentration (MBC) values against five strains of bacteria, including E. coli, S. aureus, K. pneumonia, P. aeruginosa, and MRSA, which can be easily met in our daily surrounding environments. Although these Cu-MOFs were found to be structurally very stable in aqueous medium during antibacterial activity tests, they exhibited excellent antibacterial activities against all five kinds of bacteria, including Gram-positive bacteria (S. aureus and MRSA) and Gram-negative bacteria (E. coli, K. pneumonia, and P. aeruginosa), with very low MBCs. The robust 3D frameworks with surface active metal sites rather than the small amount of leached CuII ions may participate more strongly in inactivating various kinds of bacteria and reduce potential cytotoxicity mainly caused by leached metal ions.

Selective carbon dioxide sorption by a new breathing three-dimensional Zn-MOF with Lewis basic nitrogen-rich channels.

Lewis basic heteroatoms orderly located inside the well-defined channels of metal-organic frameworks (MOFs) are potentially ideal active sites for selective gas sorption and catalysis. To develop functional MOFs with Lewis basic sites inside channels, a new C2h-symmetric dicarboxylate-based bridging ligand, 3,3'-(pyrazine-2,5-diyl)dibenzoic acid (3,3'-PDBA), was prepared by a Suzuki coupling reaction. Subsequently, two new Zn-MOFs containing the C2h-symmetric 3,3'-PDBA bridging ligand and two different bis(pyridyl)-based pillars, 1,2-bis(4-pyridyl)ethane (bpa) or 1,2-bis(4-pyridyl)ethylene (bpe), were prepared through a thermal reaction in N,N-dimethylformamide (DMF). The resulting two Zn-MOFs of the general formula of three-dimensional (3D) [Zn2(µ4-3,3'-PDBA)2(µ2-bpa)]3·(DMF)5(H2O)13 (1) or 3D-like 2D [Zn2(µ4-3,3'-PDBA)2(µ2-bpe)]·(H2O) (2) displayed primitive cubic pcu net and 2D sql net, respectively. Both Zn-MOFs 1 and 2 contain uncoordinated Lewis basic pyrazinyl nitrogen atoms in the frameworks. The solvent-free 1 with flexible bpa linkers only showed a potential porosity of 15.9% by PLATON analysis. Zn-MOF 1 with openly accessible Lewis basic sites exhibited selective sorption of CO2 over N2, H2, and CH4 at low temperature. The adsorption and desorption isotherms for CO2 sorption at 196 K showed phenomenal hysteretic behaviour indicative of a breathing process through an adsorbate-discriminatory gate-opening process toward CO2 at a low gas pressure.

Structure of poly[di-aqua-[µ-1,2-bis-(pyri-din-4-yl)ethane-κ(2) N:N']bis-(µ3-cyclo-butane-1,1-di-carboxyl-ato-κ(3) O,O':O'':O''')dimanganese(II)].

In the title compound, [Mn(C6H6O4)(C12H12N2)(H2O)] n , the cyclo-butane-1,1-di-carboxyl-ate (cbdc) ligands bridge three Mn(II) ions, forming layers parallel to the ac plane. These layers are additionally connected by 1,2-bis-(pyridin-4-yl)ethane ligands to form a three-dimensional polymeric framework. An inversion centre is located at the mid-point of the central C-C bond of the 1,2-bis-(pyridin-4-yl)ethane ligand. The coordination geometry of the Mn(II) ion is distorted octa-hedral and is built up by four carboxyl-ate O atoms, one water O atom and a pyridyl N atom. The pyridine ligand and the coordinating water mol-ecule are in a trans configuration. One carboxyl-ate group of the cbdc ligand acts as a chelating ligand towards one Mn(II) atom, whereas the second carboxyl-ate group coordinates two different Mn(II) atoms.

Synthesis and characterization of electrochemiluminescent ruthenium(II) complexes containing o-phenanthroline and various alpha-diimine ligands.

A series of o-phenanthroline-substituted ruthenium(II) complexes containing 2,2'-dipyridyl, 2-(2-pyridyl)benzimidazole, 2-(2-pyridyl)-N-methylbenzimidazole, 4-carboxymethyl-4'-methyl-2,2'-dipyridyl, and/or 4,4'-dimethyl-2,2'-dipyridyl ligands were synthesized and examined as potent electrochemiluminescent (ECL) materials. The characteristics of these complexes, regarding their electrochemical redox potentials and relative ECL intensities for tripropylamine were studied. As found in a 2,2'-bipyridyl-substituted ruthenium(II) complexes, a good correlation between the observed ECL intensity and the donor ability of alpha-diimine ligands was observed, i.e., the ECL intensity of the Ru(II) complex decreased with an increase in the ligand donor ability. The ECL efficiency increased as the number of substitutions of o-phenanthroline (o-phen) to metal complexes increased.