The development of quick and efficient methods for the detection of pathogenic bacteria is urgently needed for the diagnosis of infectious diseases and the control of microbiological contamination in global waterways, potable water sources and the food industry. This contribution will describe the synthesis of gold nanoparticles and their conjugation to broad spectrum, polypeptide and β-lactam antibiotics that function as both reducing agents and surface protectants (ATB@AuNP). Nanoparticle colloids examined using transmission electron microscopy are generally spherical in shape and range from 2–50 nm in size. Dynamic light scattering and infrared spectroscopy were also used to confirm encapsulation of the AuNP surface by antibiotic molecules. ATB@AuNP were then used to detect 3 common pathogenic bacterial species: Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The colour of the AuNP colloid was monitored visually and using UV-visible spectroscopy. A red shift of the UV visible absorbance and a visible colour change following introduction of each pathogen is indicative of ATB binding to the bacteria surface, ascribed to AuNP agglomeration. This work demonstrates that ATB@AuNP may be an efficient and high throughput tool for the rapid detection of common bacterial contaminants.

The inactivation mechanism of bacterial growth by Photodynamic Antibacterial Chemotherapy (PACT) employing gold nanoparticles and gold core/silver shell aspartame stabilized bimetallic nanoparticles was studied. Reactive oxygen species were detected and quantified, using fluorescent probes, in the first 4 h of PACT treatment on a reference strain (Staphylococcus aureus ATCC 29213) and two clinical isolates (an extended-spectrum β-lactamase-producing Escherichia coli and Pseudomonas aeruginosa). At the same time, damage of essential molecules such as proteins and lipids was found by spectrometric techniques and TEM images analysis. Overall, these results suggest that the oxidative stress caused by the photothermal effect of plasmon excitation leads to irreversible macromolecular damage and therefore to bacterial death. No signals of resistance to PACT with AuNP was found after a total of 31 passages of S. aureus treated with lower doses of the photosensitizer. All this facts support this therapy as a promising antibacterial alternative to antibiotic-resistant microbes.

Contaminated drinking water is a major health hazard in large urban areas as well as remote communities. Several pollutants detected in rivers and lakes are hormone disruptors that are harmful to consumers as well as aquatic life. In this contribution, we present a new material, synthesized using novel green technologies, designed for solar- or LED-driven degradation of pollutants. This material is based on a glass fiber support, loaded with black TiO₂, a modified form of TiO₂ with strong visible light absorption and without any toxic metal or non-metal dopants. This photocatalyst is fully compatible with flow applications. The effectiveness of the catalyst is demonstrated with crocin and 17β-estradiol, the former being a natural carotenoid used as a screening tool and the latter being a common hormonal disruptor. Our work shows that under visible light illumination, our supported black TiO₂ can degrade these water contaminants with greater efficiency than conventional TiO₂. We envision that our findings can contribute to the production of inexpensive, large-scale solar or LED-based water decontamination systems that could be rapidly deployed to sites in need. Operation of such systems would require minimal training and could be monitored remotely. In addition to the catalyst’s non-toxicity and inflow compatibility, the material also has a long shelf life and is easy and inexpensive to produce, making it an attractive candidate for developing water treatment devices.