Photo-active plasmonic nanoparticles for biomedical applications

We review our experimental activities on the exploitation of a light stimulation produced by a laser source to "activate" suitable photothermal transducers like plasmonic nanoparticles for applications in bonding and repair of biotissues, in cancer diagnostics and therapy and for drug release. Laser-assisted tissue repair or laser welding has been proposed to close chronic accidental and surgical wounds. An exemplary application is in micro-vascular surgery for the repair of arterial wounds. To this aim, we have engineered a hybrid bioadhesive consisting in a chitosan film doped with gold nanorods (GNRs) that can be activated by NIR laser light to induce a well-localized photothermal effect leading to the adhesion of the film with the arterial wall. The effectiveness of the patches to close arterial wounds has been tested in vivo in preclinical studies in rabbits. Moreover, the combination of pulsed and CW near-infrared laser light with plasmonic particles is gaining relevance for the photoacoustic imaging and photothermal ablation of cancer. Selective targeting of malignant cells with these contrast agents may rely on complementary biochemical and biological strategies, including the use of specific probes or the exploitation of cellular vehicles. Here we moved from a platform of PEGylated GNRs with plasmonic NIR bands and we implemented different approaches for active delivery by functionalization with (i) antibodies against cancer antigen 125 (CA125), which is a common biomarker for ovarian lesions; (ii) inhibitors of carbonic anhydrase 9 (CAIX), which are expressed by hypoxic cells such as those found in solid tumors; and (iii) by introducing macrophages as a versatile model of cellular vehicles that would phagocytose the particles and home to inflammatory lesions. In vitro studies on cell cultures on those different approaches will be presented and discussed. For drug release, nano-gold and other light-responsive nanomaterials can be employed for the development of an implantable device for on demand chemical release in the form of a light-activated sponge-like scaffold. The photothermal response of the gold nanoparticles contained inside the sponge triggers a contraction in proximal drug-loaded thermosensitive micelles, thus promoting the expulsion of the drug from the sponge. An advanced version of this device consists in a dispersion of graphene nano-sheets in a biopolymer matrix, which is activated by millisecond-long light pulses for confined and precisely dosed drug release.