Gold nanostars as a photoagent under the antimicrobial action of infrared (808 nm) laser radiation

Gold nanostars with an average core diameter of 122,2 nm and a spike length of 114,6 nm were synthesized and characterized at a concentration of 5,36×1010 pcs/ml with an absorption maximum of 840 nm. Gold nanostars were coated with thiolated polyethylene glycol, its amount was about 8×104 molecules per 1 particle and about 4,4×1015 molecules/ml in the colloid. The zeta potential of gold nanostars coated with PEG-SH was −2.3 mV. The combined eff ect of gold nanostars and low-intensity infrared (808 nm) laser radiation on the bacteria Staphylococcus aureus 209 P and Escherichia coli 113-13 has been studied. Incubation of suspensions of microorganisms in the presence of nanoparticles without access to light did not lead to a signifi cant reduction in the number of bacteria. Irradiation for 30 min of bacterial suspensions containing nanoparticles caused the death of 39% of the S. aureus population and 80% of the E. coli population. During the thermometry of the studied suspensions, it was found that the temperature increase is dose-dependent. The increase in temperature of the control samples that did not contain photothermal agents did not exceed 1 °C in both cases throughout the entire time of the experiment. For suspensions of bacteria (equally S. aureus and E. coli) incubated with gold nanostars during irradiation, an increase in temperature indicators, on average, by 4 °C was revealed. The more pronounced antibacterial activity of the combination of gold nanostars and infrared (808 nm) laser radiation against E. coli can also be explained by the greater sensitivity of gram-negative microorganisms to photothermal exposure

Meso-substituted cationic 3- and 4-N-Pyridylporphyrins and their Zn(II) derivatives for antibacterial photodynamic therapy

Photodynamic inactivation of microorganisms known as antibacterial photodynamic therapy (APDT) is one of the most promising and innovative approaches for the destruction of pathogenic microorganisms. Among the photosensitizers (PSs), compounds based on cationic porphyrins/ metalloporphyrins are most successfully used to inactivate microorganisms. Series of meso-substituted cationic pyridylporphyrins and metalloporphyrins with various peripheral groups in the third and fourth positions of the pyrrole ring have been synthesized in Armenia. The aim of this work was to determine and test the most effective cationic porphyrins and metalloporphyrins with high photoactivity against Gram negative and Gram positive microorganisms. It was shown that the synthesized cationic pyridylporphyrins/metalloporphyrins exhibit a high degree of phototoxicity towards both types of bacteria, including the methicillin-resistant S. aureus strain. Zinc complexes of porphyrins are more phototoxic than metal-free porphyrin analogs. The effectiveness of these Zn-metalloporphyrins on bacteria is consistent with the level of singlet oxygen generation. It was found that the high antibacterial activity of the studied cationic porphyrins/metalloporphyrins depends on four factors: The presence in the porphyrin macrocycle of a positive charge (+4), a central metal atom (Zn2+) and hydrophobic peripheral functional groups as well as high values of quantum yields of singlet oxygen. The results indicate that meso-substituted cationic pyridylporphyrins/metalloporphyrins can find wider application in photoinactivation of bacteria than anionic or neutral PSs usually used in APD

Modeling of hyperthermia induced by functionalized gold nanorods bound to Staphylococcus aureus under NIR laser radiation

In this paper, a theoretical model of the formation of a local temperature field in suspensions of microorganisms with embedded plasmonic gold nanorods under irradiation by low-intensity NIR laser light was considered. The results of numerical modeling of the optical properties of plasmon nanorods used in the experiments, and the results of multiscale modeling of the parameters of local hyperthermia with various types of distribution of the concentration of plasmon nanoparticles are presented. Found that the process of concentration of nanoparticles, functionalized with human immune globulins IgA and IgG, around the cells of microorganisms with the formation of "clouds" leads to the appearance of a microscale zone of elevated temperature. This ensures a synergistic effect of a multiplicative increase in the volume of the hyperthermia zone. The results of numerical simulation provide a justification for the experimentally observed increase in the bacterium killing ability at laser hyperthermia of the cellular environment doped with functionalized nanoparticles, without a noticeable increment in the recorded average sample temperature when irradiated with a low intensity laser beam of around 100 mW/cm2

Optical clearing of tissues: Issues of antimicrobial phototherapy and drug delivery

In the modern world, with a poor environmental situation, there is a certain ‘‘erasure” of the boundaries between pathogenic, opportunistic microorganisms and commensals, the number of antibiotic-resistant bacterial strains is growing. The microbiome of the human body is made up of more than 500 types of microorganisms, representing an integral ecological system, which is in a state of dynamic equilibriumwith macroorganism. Colonization of various biotopes is carried out by the formation of a biofilm, which represents several layers of microorganisms covered with a common glycocalyx and enclosed in a highly hydrated exopolysaccharide-mucin matrix. Under certain conditions, opportunistic bacteria can become causative agents of purulentinflammatory diseases, i.e. the mechanism of autoinfection is realized with a decrease in the body’s resistance or their translocation into unusual biotopes

Thermal optics of ordered arrays of plasmon nanoparticles in context of SERS, cell optoporation, and pathogen destruction

Numerical modeling of spectral absorption and scattering properties of structures manufactured as the ordered arrays of plasmon nanoparticles is carried out in this work. The results of numerical 2D simulation of selective heating of an array of plasmon resonant gold nanodiscs irradiated by a CW NIR laser (810 or 1064 nm) are presented. Calculations fit well to experimental data received. We demonstrate the possibility to control the local amplification of a shining laser field in the space between nanodiscs, as well as plasmon resonance absorption of each individual nanodisc. The perspectives of application of such nanostructures for providing of precision dosed-up thermal effects in cells and biological tissues are discussed