Near-infrared absorbing solid lipid nanoparticles encapsulating plasmonic copper sulfide nanocrystals

A novel near-infrared-absorbing nanoformulation is fabricated by efficiently encapsulating plasmonic Cu2-xS nanocrystals (NCs) within the core of low-density lipoprotein (LDL)-mimetic solid lipid nanoparticles (SLNs). Cu2-xS NCs are ideal candidates as photothermal or imaging agents for in vivo cancer treatment, thanks to their plasmonic properties, low toxicity, biodegradability, and low cost. Their incorporation in the LDL-mimetic nanocarriers enhances the nanoformulation potential in biomedical applications, resulting in nanosystems able to provide the concomitant delivery of anticancer molecules and cancer diagnosis and/or therapy. Besides the comprehensive characterization of the prepared nanostructures, the paper aims to tackle the accurate determination of the NC concentration in the final nanoformulation. Since both photothermal therapy and imaging efficiency strongly depend on the concentration of the nanoagents, the availability of a real-time and nondestructive approach for the determination of NC concentration in the SLNs is essential for clinical studies addressing the possible administration of the nanoformulation for in vivo applications. Here, the Mie theory and Drude model-based fitting procedure of the experimental results from the morphological and spectroscopic characterization is proposed for the explanation of the plasmonic properties of the nanoformulation and for the determination of the concentration in terms of Cu2-xS NCs and SLNs.