Measurement of excited singlet oxygen molecule in a vacuum sterilization system, using electric spin resonance (ESR) with a water-soluble polymer thin film

Cationic porphyrin-based nanoparticles for photodynamic inactivation and identification of bacteria strains

The emergence of antibiotic drug resistance has undermined the efficacy of antibiotics, and is becoming a severe threat to public health. To combat antibiotic drug resistance and to replace traditional antibiotic treatment, an alternative strategy based on antibacterial photodynamic therapy (APDT), which has broad applicability, high efficiency and less potential of developing antibiotic drug resistance, has been developed. In this work, the cationic porphyrin-based nanoparticles (NPs) were prepared by epoxy-amine chain extension polymerization of diepoxy-terminated poly(ethylene glycol) (PEG) and tetraamino-containing porphyrin, followed by quaternization with methyl iodine and butyl bromide. The as-obtained cationic porphyrin NPs preserved the photophysical properties of porphyrin derivatives, and can efficiently generate singlet oxygen (¹O₂) under 635 nm laser irradiation. The cationic porphyrin-based NPs displayed intrinsic antibacterial properties, and exhibited strong APDT effect on Gram-positive bacteria by destroying the bacterial cell membranes. Upon incubation with different bacterial strains, it was found that they could be utilized to identify Gram-positive bacteria by observing the sedimentation behavior of their mixtures, and visualizing their co-cultured and centrifugal bacteria cakes. In addition, the cationic porphyrin-based NPs had good hemocompatibility and low dark cytotoxicity.

Designing and application of a new medical instrument sterilization system using reactive oxygen species

The aim of this study is to design and test a new medical sterilization system as an alternative to the techniques used in the sterilization of medical instruments. The designed system, which uses a new oxygen molecule allotrope (NOMA) in the reactive oxygen species, is developed as an alternative to the sterilization systems using other gases. The test was conducted on 12 different materials, each having a surface of 2 cm², sterilized under 120 °C at 1 atm pressure for 20 min in the NUVE-OT 4060 sterilizer, and all surfaces were contaminated with a biological indicator Geobacillus stearothermophilus cultured in an incubator at 37 °C. Test samples in sterile Petri dishes were placed in a desiccator, and a sample was taken at 30-, 45-, and 60-min test periods and were placed on an agar medium and put in a Memmert incubator IN75 at 37 °C; in the controls conducted following 16-18 h of incubation period, no bacterial growth was observed in the newly designed system tested with gram positive bacilli; moreover, it was observed that the new system was 100% effective in sterilizing the microbes as no growth was observed on the samples. Within the scope of this study, a faster, low-cost, low-temperature, residue-free, and human and environmental friendly system was developed and tested for sterilization of medical devices compared to existing sterilization methods using NOMA.

Combination of microwave discharge electrodeless lamp and a TiO2/HZSM-5 composite for the photocatalytic degradation of dimethyl sulphide

In this study, an integrated photocatalytic system consisting of a microwave discharge electrodeless lamp (MDEL) and TiO₂/HZSM-5 was established to investigate the intensified degradation of dimethyl sulphide (DMS). The system targets optimisation of the reactive oxygen species (ROS) and photocatalytic degradation pathways without catalyst deactivation. TiO₂/HZSM-5, containing highly dispersed TiO₂ nanoparticles, was prepared through the sol-gel method. TiO₂/HZSM-5 exhibits strong acidity and can adsorb DMS in multiple adsorption forms. Thus, the adsorption capacity of TiO₂/HZSM-5 is 20 and 53 times higher than that of Aeroxide TiO₂ (P25) in dry and highly humid air, respectively. UV-Vis analysis was performed to investigate the ROS in the gas phase. The results show that the concentrations of the ROS increased by 8% and 62.7% in dry and highly humid air, respectively. ¹O₂ and O (¹D), as well as ·OH are the major ROS, accounting for 73.6% and 61.6% in dry and highly humid air, respectively. A total of 92.5% DMS was removed over 600 min in dry air. Microwaves have strong desorption effects on absorbed substances, promoting the degradation of DMS via ROS in the gas phase. Moreover, ¹O₂, O (¹D), and ·OH can mineralise more DMS molecules into SO₂ and SO₃ through methanesulfonic acid. The highest mineralisation rate of 89.48% was obtained at 90% humidity over 600 min without catalyst deactivation. Therefore, this integrated system induced by microwave radiation can improve ROS production and prevent catalyst deactivation, providing an alternative to achieve higher photocatalytic performances in dry and highly humid air.

Graphene oxide as a cartridge enable on-line assembly of photosensitizer for 1O2-based electrochemical aptasensing

An ultrasensitive ¹O₂-based electrochemical aptasensor by on-line assembly of photosensitizers using graphene oxide (GO) as a cartridge is reported. In the presence of target protein lysozyme, the interaction of lysozyme with aptamer led to the dissociation of dsDNA and release of the aptamer-lysozyme complex to solution, with DNA-c retaining on the electrode; then, the photosensitizer phloxine B (PB) was assembled on the electrode since GO can simultaneously adsorb DNA-c and PB molecules. Upon irradiation by a green LED, ¹O₂ was generated by photocatalysis of PB molecules and then cleaved the DNA-c, leading to remarkably decreased impedance signals that linearly respond with the logarithm of lysozyme concentration. Benefitting from the efficient photosensitization ability of PB and the high PB-loading capacity of GO, the developed sensor allowed determination of 0.001 to 100 nM lysozyme with a limit of detection of about 0.14 pM. The relative standard deviation (RSD) for five independent electrodes with 1 nM lysozyme was 3.1%, indicating satisfactory reproducibility. The sensor also showed excellent selectivity toward lysozyme in the presence of interfering substances and was applied to the determination of lysozyme in urine samples with recoveries ranging from 91 to 101%. The on-line assembly of photosensitizer technique opens a new way for amplified electrosensing of biomolecules. Graphical abstract An on-line assembly of photosensitizers and DNA on electrode was developed using graphene oxide a cartridge and the photocatalytic electrosensor can be used for label-free detection of lysozyme as low as 1 pM.

A covalent triazine framework as an oxidase mimetic in the luminol chemiluminescence system: application to the determination of the antioxidant rutin

It is found that a covalent triazine framework (CTF-1) (that was prepared from 1,4-dicyanobenzene) exhibits oxidase-like activity toward the oxidation of luminol with dissolved oxygen in alkaline condition to produce intense blue chemiluminescence (CL). The reaction follows Michaelis-Menten kinetics and shows strong specificity for luminol. Reactive oxygen species including ¹O₂, ^•OH and O₂^•- are testified to be involved in the reaction and responsible for the CL. The reaction was applied to the determination of the radical-scavenging activity of antioxidants, with rutin, kaempferol and ferulic acid serving as model scavengers. A sensitive CL method was developed for the determination of rutin based on its inhibitory effect on the reaction. The CL system gave a linear response to the concentration of rutin in the range of 0.03-0.25 μmol·L^-1 with a limit of detection of 0.015 μmol·L^-1. The practicability of the method was demonstrated by successful determination of rutin in tablets and in Flos Sophorae Immaturus. Graphical Abstract.

Investigation of reactive oxygen species produced by microwave electrodeless discharge lamp on oxidation of dimethyl sulfide

Microwave electrodeless discharge lamp (MEDL) has been regarded as a powerful light source of photoreaction. Four kinds of chemicals, nitrogen (N₂), oxygen (O₂), water (H₂O) and dimethyl sulfide (DMS), were used as molecular probes to explore the generation process of reactive oxygen species (ROS) and their photo-oxidation performances on the photodegradation of organic pollutants with application of an exterior MEDL system. ROS such as O (³P), O₃, O (¹D) and ¹O₂ were generated via irradiation of O₂ and H₂O except dry N₂ by MEDL. They were transformed to other ROS including ·OH and H₂O₂ with increase of relative humidity. The ROS productivity was inhibited evidently by humidity and ·OH became the major active species at high humidity. An optimal mineralization rate of 23.6% for DMS photodegradation was reached in dry air compared with 8.74% at high humidity, which indicated that O (¹D) and ¹O₂ were more powerful oxidants than O₃ and OH. The results showed that the higher mineralization rate of organic pollutants was obtained by increasing the generation efficiency of ROS of O (¹D) and ¹O₂. Furthermore, the results provided an alternative to develop intensification technology on photodegadation of organic pollutants with MEDL system and an optimal operation process including photocatalyst and humidity.