Search

Antibiotic resistance is one of the world's most urgent public health problems. Antimicrobial photodynamic therapy (aPDT) is a promising therapy to combat the growing threat of antibiotic resistance. The aPDT combines a photosensitizer and light to generate reactive oxygen species to induce bacterial inactivation. Ruthenium polypyridyl complexes are significant because they possess unique photophysical properties that allow them to produce reactive oxygen species upon photoirradiation, which leads to cytotoxicity. These antimicrobial agents cause bacterial cell death by DNA and cytoplasmic membrane damage. This article presents a comprehensive review of photoactive antimicrobial properties of kinetically inert and labile ruthenium complexes, nanoparticles coupled photoactive ruthenium complexes, and photoactive ruthenium nanoparticles. Additionally, limitations of current ruthenium‐based photoactive antimicrobial agents and future directions for the development of antibiotic‐resistant photoactive antimicrobial agents are discussed. It is important to raise awareness for the ruthenium‐based aPDT agents in order to develop a new class of photoactive metalloantibiotics capable of combating antibiotic resistance. [ABSTRACT FROM AUTHOR]

Antibiotic resistance is one of the world's most urgent public health problems. Antimicrobial photodynamic therapy (aPDT) is a promising therapy to combat the growing threat of antibiotic resistance. The aPDT combines a photosensitizer and light to generate reactive oxygen species to induce bacterial inactivation. Ruthenium polypyridyl complexes are significant because they possess unique photophysical properties that allow them to produce reactive oxygen species upon photoirradiation, which leads to cytotoxicity. These antimicrobial agents cause bacterial cell death by DNA and cytoplasmic membrane damage. This article presents a comprehensive review of photoactive antimicrobial properties of kinetically inert and labile ruthenium complexes, nanoparticles coupled photoactive ruthenium complexes, and photoactive ruthenium nanoparticles. Additionally, limitations of current ruthenium‐based photoactive antimicrobial agents and future directions for the development of antibiotic‐resistant photoactive antimicrobial agents are discussed. It is important to raise awareness for the ruthenium‐based aPDT agents in order to develop a new class of photoactive metalloantibiotics capable of combating antibiotic resistance. [ABSTRACT FROM AUTHOR]

A series of nickel bis(diphosphine) complexes with dipeptides appended to the ligands were investigated for the catalytic oxidation of formate to carbon dioxide, a proton, and two electrons. Typical rates of approximately 7 s-1 were found, similar to that for the parent complex (ca. 8 s-1), with amino acid size and positioning contributing very little to the rate or operating potential. Hydroxy functionalities did result in lower rates, which were recovered by protecting the hydroxy group. The results suggest that the overall dielectric properties introduced by the dipeptides do not play an important role in catalysis, but free hydroxy groups do influence activity, implying contributions from intra- or intermolecular interactions. These observations are important in developing a fundamental understanding of the effect that an enzyme-like outer coordination sphere can have upon molecular catalysts. [ABSTRACT FROM AUTHOR]

The outer-coordination sphere of enzymes acts to fine-tune the active site reactivity and control catalytic rates, suggesting that incorporation of analogous structural elements into molecular catalysts may be necessary to achieve rates comparable to those observed in enzyme systems at low overpotentials. In this work, we evaluate the effect of an amino acid and dipeptide outer-coordination sphere on [Ni(PPh2NPh-R2)2]2+ hydrogen production catalysts. A series of 12 new complexes containing non-natural amino acids or dipeptides was prepared to test the effects of positioning, size, polarity and aromaticity on catalytic activity. The non-natural amino acid was either 3-( meta- or para-aminophenyl)propionic acid terminated as an acid, an ester or an amide. Dipeptides consisted of one of the non-natural amino acids coupled to one of four amino acid esters: alanine, serine, phenylalanine or tyrosine. All of the catalysts are active for hydrogen production, with rates averaging ∼1000 s−1, 40 % faster than the unmodified catalyst. Structure and polarity of the aliphatic or aromatic side chains of the C-terminal peptide do not strongly influence rates. However, the presence of an amide bond increases rates, suggesting a role for the amide in assisting catalysis. Overpotentials were lower with substituents at the N-phenyl meta position. This is consistent with slower electron transfer in the less compact, para-substituted complexes, as shown in digital simulations of catalyst cyclic voltammograms and computational modeling of the complexes. Combining the current results with insights from previous results, we propose a mechanism for the role of the amino acid and dipeptide based outer-coordination sphere in molecular hydrogen production catalysts. [ABSTRACT FROM AUTHOR]