Facile construction of fluorescent C70-COOH nanoparticles with advanced antibacterial and anti-biofilm photodynamic activity

Photodynamic antibacterial therapy has been considered as one of the most promising treatments to alleviate the spread of multidrug resistant bacterial pathogens. Given the hypoxic environment of infectious tissues, photosensitizers with reduced oxygen-demand could exhibit superiority upon irradiation. Herein reported is a novel C₇₀-based photosensitizers synthesized by the facile one-step thiol-ene reaction. Various characterization techniques were employed to confirm the structural, photoluminescent properties, photostability and biocompatibility of the as-synthesized C₇₀-COOH nanoparticles. Furthermore, they were capable of efficiently producing reactive oxygen species following both the type I and II mechanistic pathways, thus still generating adequate free radicals under hypoxic condition. Therefore, they could approach and destroy the bacterial cell membrane in the presence of visible light, thereby causing cytoplasmic leakage and eventually achieving broad-spectrum inactivation of four representative bacterial strains. Especially, methicillin-resistant Staphylococcus aureus (MRSA) were completely eliminated after merely 10 minutes irradiation, and the formation of its corresponding biofilm were also greatly inhibited by C₇₀-COOH nanoparticles. These results provide new insights and opportunities for the development of hypoxia-tolerant fullerene-based photosensitizers to combat multidrug resistant bacterial and related infections.

Voltammetric sensor for the monitoring of hazardous herbicide triclopyr (TCP)

The herbicide Triclopyr (TCP) is widely applied to minimize the growth of woody plants. Monitoring of TCP is of major environmental concern due to its adverse impact on aquatic organisms, soils and animals. Electrochemical behavior of TCP was investigated at C₇₀ decorated PANI modified glassy carbon sensor (PANI/C₇₀/GC). The experimental parameters, such as concentration, pH, amplitude, frequency, deposition potential were optimized. The modified sensor exhibited an excellent catalytic response towards the reduction of TCP with a well-defined reduction peak at 1.72 V. The developed sensor was characterized by scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). The electrochemical measurements were carried out using square wave (SWV) and cyclic voltammetry (CV). The modified sensor exhibited linear calibration curve for TCP over a concentration range of 10 ngmL^-1-100 ngmL^-1 with detection limit of 1.9 ngmL^-1. The developed sensor could detect TCP efficiently without any interference from the common metabolites. The voltammetric procedure was applied successfully to real sample analysis with high sensitivity and good selectivity.

Photochemical reactivity of aqueous fullerene clusters: C60 versus C70

Over the past few years, there has been a strong interest in exploring the potential impact of fullerenes in the environment. Despite that both C₆₀ and C₇₀ have been detected in environmental matrices, the research on the impact of higher fullerenes, such as C_70, has been largely missing. This study evaluated and compared the phototransformation of aqueous C₆₀ and C₇₀ clusters (nC₆₀ and nC₇₀) and their ¹O₂ production under sunlight and lamp light irradiation (315nm, 360nm and 420nm). The nC₆₀ and nC₇₀ samples formed by direct mixing with water adopted a face-centered cubic (FCC) crystal structure. The apparent quantum yields (AQYs) of fullerene phototransformed were relatively constant over the examined wavelengths, while ¹O₂ production AQYs decreased with increased wavelengths. The long-term fate studies with outdoor sunlight indicated that both nC₆₀ and nC₇₀ lost considerable organic carbon contents (>80%) in water after ∼8 months of irradiation and that the intermediate photoproducts of nC₆₀ and nC₇₀ exhibited a progressively increased level of oxygen-containing functionalities. Overall, the study indicates that nC₇₀ can be photochemically removed under sunlight conditions and that the photoreactivity of nC₆₀ based on AQYs is greater than that of nC₇₀.

Liquid chromatography-atmospheric pressure photoionization-Orbitrap analysis of fullerene aggregates on surface soils and river sediments from Santa Catarina (Brazil)

In the present work, a new analytical approach is proposed for the analysis of seven fullerenes (C₆₀, C₇₀, N-methylfulleropyrrolidine, [6,6]-phenyl C₆₁ butyric acid methyl ester, [6,6]-thienyl C61 butyric acid methyl ester, C60 pyrrolidine tris-acid ethyl ester and [6,6]-phenyl C₇₁ butyric acid methyl ester fullerenes) in soils and sediments. This procedure combines an ultrasound-assisted solvent extraction (UAE) with toluene followed by liquid chromatography (LC), using a pyrenylpropyl group bonded silica based column, coupled to a high-resolution mass spectrometer (HRMS) using atmospheric pressure photoionisation (APPI) in negative ion mode. The analytical performance for fullerene separation of the pyrenylpropyl group bonded silica column was compared to the C18 column. For the ultra-trace analysis of fullerenes in complex environmental samples, the use of the APPI source and the use of the electrospray ionisation (ESI) source were compared. Using this approach for the analysis of fullerenes in complex matrices, a series of advantages, in terms of sensitivity and specificity, have been demonstrated. The method limits of detection (MLOD) and the method limits of quantification (MLOQ) in soils and sediments ranged from 0.022 to 0.39 pg/g and from 0.072 to 1.3 pg/g, respectively. Recoveries were between 68 and 106%. The analytical method was applied in order to assess the occurrence of selected fullerenes in 45 soils of Sul Catarinense (Santa Catalina State, Brazil) and 15 sediments from the Tubarão River, presenting different pressures of contamination: a coal-combustion power plant, car exhaust, coal mining industry and wastewater effluents. C₆₀ and C₇₀ fullerenes have been detected at concentrations ranging from the MLOD to 0.150 ng/g. None of the functionalised fullerenes were detected in any of the samples. Combustion processes, in particular car exhaust, were identified as the main source of fullerenes. However, the potential degradation of residual concentrations of engineered fullerenes to more stable forms, such as C₆₀ and C₇₀, should also be considered.