Plasmonic gold nanoparticles for detection of fungi and human cutaneous fungal infections

Abstract

Fungi, which are common in the environment, can cause a multitude of diseases. Warm, humid conditions allow fungi to grow and infect humans via the respiratory, digestive and reproductive tracts, genital area and other bodily interfaces. Fungi can be detected directly by microscopy, using the potassium hydroxide test, which is the gold standard and most popular method for fungal screening. However, this test requires trained personnel operating specialist equipment, including a fluorescent microscope and culture facilities. As most acutely infected patients seek medical attention within the first few days of symptoms, the optimal diagnostic test would be rapid and self-diagnostic simplifying and improving the therapeutic outcome. In suspensions of gold nanoparticles, Aspergillus niger can cause a colour change from red to blue within 2 min, as a result of changes in nanoparticle shape. A similar colour change was observed in the supernatant of samples of human toenails dispersed in water. Scanning electron microscopy, UV/Vis and Raman spectroscopy were employed to monitor the changes in morphology and surface plasmon resonance of the nanoparticles. The correlation of colour change with the fungal infection was analysed using the absorbance ratio at 520 nm/620 nm. We found a decrease in the ratio when the fungi concentration increased from 1 to 16 CFU/mL, with a detection limit of 10 CFU/mL. The test had an 80% sensitivity and a 95% specificity value for the diagnosis of athlete's foot in human patients. This plasmonic gold nanoparticle-based system for detection of fungal infections measures the change in shape of gold nanoparticles and generates coloured solutions with distinct tonality. Our application has the potential to contribute to self-diagnosis and hygiene control in laboratories/hospitals with fewer resources, just using the naked eye. Graphical abstract Colorimetric method for fungi detection with gold nano particles.

Plasmonic rK28 ELISA improves the diagnosis of canineLeishmaniainfection

“…Plasmonic ELISAs have been used to investigate the diagnosis of different diseases, including cancer, HIV and fungal and bacterial infections, using a capture ELISA protocol and have shown several advantages in relation to sensitivity. However, only one report has described a bacterial diagnosis using an indirect ELISA protocol .…”

“…Although pELISA has been used to investigate different diseases, including cancer, HIV and fungal and bacterial infections, its use in diagnosing CanL has not been investigated. Recently, we developed and successfully tested an indirect pELISA on canine sera positive and negative for Leishmania spp.…”

Developing Gold Nanoparticles-Conjugated Aflatoxin B1 Antifungal Strips

“…The characteristics of the SPR depend on the nanoparticle size, which can strongly influence the resonant frequency that determines the characteristic colour, which is observable by the naked eye [34]. The associated colour can be employed for fungal detection [35]. The colour changes from red to purple/blue are sufficient for detection by the naked eye.…”

“…Di Nardo et al have employed blue (desert rose-like, mean diameter ca.75 nm) AuNPs in order to produce different colour bands of LFIAs [32,33]. There is a strong association between the AuNPs formulation and colour change [34,35]. The associated colour can be employed for a number of applications and, therefore, continued refinement of AuNPs synthesis can provide desirable bands for LFIAs.This study aims to develop a small gold nanoparticle (AuNP) immunochromatographic strip for detecting AFB1 in food samples.…”

Investigating the Role of Shape and Size of Gold Nanoparticles on Their Toxicities to Fungi

“…The formation time of GNPs was recorded, defined as the amount of time from the start of the reaction to the time point at which the ratio of the light absorption of GNPs at 540 nm (A540) and the absorption at 450 nm (A450) was higher than 1 [32][33][34].…”