Noble metal nanoparticles applications in cancer

Abstract

Nanotechnology has prompted new and improved materials for biomedical applications with particular emphasis in therapy and diagnostics. Special interest has been directed at providing enhanced molecular therapeutics for cancer, where conventional approaches do not effectively differentiate between cancerous and normal cells; that is, they lack specificity. This normally causes systemic toxicity and severe and adverse side effects with concomitant loss of quality of life. Because of their small size, nanoparticles can readily interact with biomolecules both at surface and inside cells, yielding better signals and target specificity for diagnostics and therapeutics. This way, a variety of nanoparticles with the possibility of diversified modification with biomolecules have been investigated for biomedical applications including their use in highly sensitive imaging assays, thermal ablation, and radiotherapy enhancement as well as drug and gene delivery and silencing. Here, we review the available noble metal nanoparticles for cancer therapy, with particular focus on those already being translated into clinical settings.

Figure 1

Noble metal NPs for cancer therapy. Once the tumor is directly connected to the main blood circulation system, NPs can exploit several characteristics of the newly formed vasculature and efficiently target tumors. Tumor cells are supplied by blood capillaries that perfuse the cells of the tissue where NPs can (i) passively accumulate or (ii) anchor through targeting moieties to biomarkers overexpress by tumor cells. NPs can act simultaneously as therapeutic agents, inducing hyperthermia, enhancing radiotherapy, silencing genes, and/or delivering drugs to induce tumor cell death, and as imaging enhancers or contrast agents, to help tracking the therapeutic effects in real time.

Figure 2

Multifunctional NP-based systems for tumor targeting, delivery and imaging. These innovative NPs comprise nucleic acids, aptamers and anticancer drug molecules for delivery to the target tissue. Depending on the targeting mechanism, they can be on the surface or inside the NPs. Responsive NPs/molecules can also trigger reaction upon external stimuli through the functionality of valuable tumor markers, peptides, polymers and antibodies that can used to improve NP circulation, effectiveness and selectivity. Multifunctional systems can carry reporter molecules tethered to the particle surface and employed as tracking and/or contrast agents.