Nanotechnologies are increasingly being developed for medical purposes. However, these nanomaterials require ultrastability for better control of their pharmacokinetics. The present study describes three types of ultrastable gold nanoparticles stabilized by thiolated polyethylene glycol groups remaining intact when subjected to some of the harshest conditions described thus far in the literature, such as autoclave sterilization, heat and freeze-drying cycles, salts exposure, and ultracentrifugation. Their stability is characterized by transmission electron microscopy, UV-visible spectroscopy, and dynamic light scattering. For comparison purposes, two conventional nanoparticle types were used to assess their colloidal stability under all conditions. The ability of ultrastable gold nanoparticles to encapsulate bimatoprost, a drug for glaucoma treatment, is demonstrated. MTS assays on human corneal epithelial cells is assessed without changing cell viability. The impact of ultrastable gold nanoparticles on wound healing dynamics is assessed on tissue engineered corneas. These results highlight the potential of ultrastable gold nanoparticles as a drug delivery system in ocular therapy.

A large number of drugs are administered on different mucosal surfaces. However, due to the poor mucoadhesion of the current formulations, their bioavailability is often very low. The development of efficient mucoadhesive drug delivery systems is thus crucial for improving the performance of these drugs. The mucoadhesive properties of gold nanoparticles were investigated. First, two types of gold nanoparticles were synthesized: AuNP1 and AuNP2. AuNP1 only contain internal thiol groups on their metallic core, and AuNP2 contain both internal and peripheral thiol groups. Different protocols based on an adapted quantitative colorimetric method, UV-visible and fluorescence spectroscopies were then developed to gather information on their mucoadhesive properties. Moreover, a global correction factor for the inner filter effect in spectrofluorimetry was proposed, and the data obtained were compared to those commonly used in the literature. Mucins deeply interact with AuNP1, perturbing their core, whereas they remain at the periphery of AuNP2. The quantitative method suggests that a larger number of mucins interact with AuNP2. The establishment of this protocol could be applied to assess the mucoadhesive properties of other stable molecules. This mucoadhesive property of gold nanoparticles could be combined with their drug delivery ability in order to improve the medication administered on mucosa.

The rapid electrochemical identification and quantification of neurotransmitters being a challenge in the ever-growing field of neuroelectronics, we aimed to facilitate the electrochemical selective detection of dopamine by functionalizing commercially available electrodes through the deposition of a thin film containing pre-formed gold nanoparticles. The influence of different parameters and experimental conditions, such as buffer solution, fiber material, concentration, and cyclic voltammetry (CV) cycle number, were tested during neurotransmitter detection. In each case, without drastically changing the outcome of the functionalization process, the selectivity towards dopamine was improved. The detected oxidation current for dopamine was increased by 92%, while ascorbic acid and serotonin oxidation currents were lowered by 66% under the best conditions. Moreover, dopamine sensing was successfully achieved in tandem with home-made triple electrodes and an in-house built potentiostat at a high scan rate mode.

On the cover: The cover image, by Florence Masse et al., is based on the Review Article Gold nanoparticles in ophthalmology, DOI: 10.1002/med.21509.