Rising concerns over multidrug-resistant bacteria have necessitated an expansion to the current antimicrobial arsenal and forced the development of novel delivery strategies that enhance the efficacy of existing treatments. Antimicrobial peptides (AMPs) are a promising antibiotic alternative that physically disrupts the membrane of bacteria, resulting in rapid bactericidal activity; however, clinical translation of AMPs has been hindered by their susceptibility to protease degradation. Through the co-loading of liposomes encapsulating model AMP, IRIKIRIK-CONH2 (IK8), and gold nanorods (AuNRs) into a poly­(ethylene glycol) (PEG) hydrogel, we have demonstrated the ability to protect encapsulated materials from proteolysis and provide the first instance of the triggered AMP release. Laser irradiation at 860 nm, at 2.1 W cm–2, for 10 min led to the photothermal triggered release of IK8, resulting in bactericidal activity against Gram-negative Pseudonomas aeruginosa and Gram-positive Staphylococcus aureus. Furthermore, by increasing the laser intensity to 2.4 W cm–2, we have shown the thermal enhancement of AMP activity. The photothermal triggered release, and enhancement of AMP efficacy, was demonstrated to treat two rounds of fresh S. aureus, indicating that the therapeutic gel has the potential for multiple rounds of treatment. Taken together, this novel therapeutic hydrogel system demonstrates the stimuli-responsive release of AMPs with photothermal enhanced antimicrobial efficacy to treat pathogenic bacteria.

High purity gold nanorods (AuNRs) with tunable morphology have been synthesized through a binary-surfactant seedless method, which enables the formation of monocrystalline AuNRs with diameters between 7 and 35 nm. The protocol has high shape yield and monodispersity, demonstrating good reproducibility and scalability allowing synthesis of batches 0.5 l in volume. Morphological control has been achieved through the adjustment of the molar concentrations of cetyltrimethylammonium bromide and sodium oleate in the growth solution, providing fine tuning of the optical scattering and absorbance properties of the AuNRs across the visible and NIR spectrum. Sodium oleate was found to provide greatest control over the aspect ratio (and hence optical properties) with concentration changes between 10 and 23 mM leading to variation in the aspect ratio between 2.8 and 4.8. Changes in the geometry of the end-caps were also observed as a result of manipulating the two surfactant concentrations.

Recently, the combination of metallic nanoparticles (NPs) of Au, Ag, Fe2O3, and Fe3O4 with traditional soft matter drug‐delivery systems has emerged as a promising strategy to achieve site‐specific and controlled release of antimicrobial agents. By harnessing the plasmonic and magnetic properties of inorganic NPs, the disruption of antibiotic‐loaded liposomes, polymersomes, and hydrogels can be remotely triggered by mechanisms such as photo‐ and magneto‐thermal effects, microbubble cavitation, magnetic positioning, and pH‐changes, hence offering significant advantages in improving antibacterial efficacy, reducing side effects, and in overcoming antimicrobial resistance. This review highlights the latest development of stimuli‐responsive antibiotic delivery systems incorporating inorganic NPs. The methods employed for preparation of hybrid inorganic NP‐associated drug‐delivery systems and the effects this has upon the system are discussed. Finally, a detailed exposition of the NP‐mediated triggering mechanisms is provided and pertinent examples of their use in antimicrobial applications are presented.

Inorganic nanoparticles have long been applied as catalysts and nanozymes with exceptional rate constants arising from their large surface areas. While it is understood that high surface area-to-volume ratios and low average atomic coordination are responsible for their exceptional catalytic properties, these facets remain under exploited in the design of gold nanoparticle catalysts and nanozymes. Here we have developed 3D, 2D, and quasi-1D gold nanoparticles for use as catalysts in reducing 4-nitrophenol by sodium borohydride. Each morphology was characterised with transmission electron microscopy and UV-Vis absorption spectroscopy, while the highest catalytic activity was achieved when the perimeter-to-surface area, or amount of ‘edge’, was maximised. The particles were then applied as nanozymes in modular nano-composite hydrogels. Independent hydrogel tiles containing either the substrate or catalyst were bonded in stacks, which allowed reagent transport across their interface for the colourimetric detection of hydrogen peroxide. This work presents novel insight into the catalytic activity of low-dimension nanoparticles and their potential application in nanozyme-based diagnostic devices.

Gold nanorods (AuNRs) have attracted a great deal of attention due to their potential for use in a wide range of biomedical applications. However, their production typically requires the use of the relatively toxic cationic surfactant cetyltrimethylammonium bromide (CTAB) leading to continued demand for protocols to detoxify them for in vivo applications. In this study, a robust and facile protocol for the displacement of CTAB from the surface of AuNRs using phospholipids is presented. After the displacement, CTAB is not detectable by NMR spectroscopy, surface‐enhanced Raman spectroscopy, or using pH‐dependent ζ‐potential measurements. The phospholipid functionalized AuNRs demonstrated superior stability and biocompatibility (IC50 > 200 µg mL−1) compared to both CTAB and polyelectrolyte functionalized AuNRs and are well tolerated in vivo. Furthermore, they have high near‐infrared (NIR) absorbance and produce large amounts of heat under NIR illumination, hence such particles are well suited for plasmonic medical applications.

depends on their NIR optical absorption for photoresponses, and their structure and surface properties leading to low cytotoxicity and efficient cellular uptake. An important challenge for photo-triggered nanocarriers lies in their cellular confinement within membrane-bound vacuoles. [9] This can limit therapeutic benefit by adversely modifying their optical properties due to agglomeration, [10] or reducing the efficacy of delivering therapeutic payloads by phototriggered drug release. [11,12] Recent studies have revealed that silicon nanowires with lengths of several micrometers can enter cells via nonendocytic pathways and demonstrate cytosolic distribution. [13] We hypothesized that NIR-active 1D nanomaterials with similar structural parameters might circumvent the drawbacks of vesicular confinement. Gold nanotubes (AuNTs) represent an intriguing subset of 1D nanomaterials. Their accessible inner cavity can in principle be loaded with drugs, [14,15] their open ends can be used as gates for controlled drug release, [16] and their lower heat capacity enables better pulse heating for photoacoustic imaging and photothermal therapy. [17] Despite the potential merits of AuNTs, their lack of NIR absorption and our limited understanding of cellular interactions have hindered their exploitation. For example, the pentagonal AuNTs synthesized by Bi and The generation of effective and safe nanoagents for biological applications requires their physicochemical characteristics to be tunable, and their cellular interactions to be well characterized. Here, the controlled synthesis is developed for preparing high-aspect ratio gold nanotubes (AuNTs) with tailorable wall thickness, microstructure, composition, and optical characteristics. The modulation of optical properties generates AuNTs with strong near infrared absorption. Surface modification enhances dispersibility of AuNTs in aqueous media and results in low cytotoxicity. The uptake and trafficking of these AuNTs by primary mesothelioma cells demonstrate their accumulation in a perinuclear distribution where they are confined initially in membrane-bound vesicles from which they ultimately escape to the cytosol. This represents the first study of the cellular interactions of high-aspect ratio 1D metal nanomaterials and will facilitate the rational design of plasmonic nanoconstructs as cytosolic nanoagents for potential diagnosis and therapeutic applications.

Two errors have been found in paragraph 2 of section 2.2. An incorrect volume for the amount of AgNO3 solution added and the order in which solutions were added is wrong.

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