Biomimetic synthesis of 2D ultra-small copper sulfide nanoflakes based on reconfiguration of the keratin secondary structure for cancer theranostics in the NIR-II region

Two-dimensional transition metal dichalcogenides have attracted widespread attention in cancer theranostics due to their high specific surface area and excellent photothermal conversion properties. However, their dimensions and biodegradability have limited the exploration of the therapeutic properties of transition metal dichalcogenides. Herein, we explore the mechanism of the keratin alpha-helix-to-random coil transition, as an actuation mechanism for the controllable design and precise synthesis of two-dimension copper sulfide nanoflakes (CuS NFs) with high absorption in the NIR-II window. Upon mixing keratin and Cu2+, the hydrogen bonds that maintain the alpha-helix are broken by copper ions to form biuret coordination, while the structure of the alpha-helix is transformed into a random coil, providing a more scalable space for the growth of CuS NFs. The CuS NFs prepared in this way possess the great advantages of outstanding uniformity, size controllability, and biodegradability. Importantly, the CuS NFs in the NIR-II window show an excellent photothermal conversion efficiency (32.9%) and extraordinary photoacoustic signal. This work updates the fabrication of two-dimensional transition metal dichalcogenides and greatly enhances their competitiveness in the area of cancer theranostics in the NIR-II region, and provides significant theoretical and practical opportunities for the development of keratin using biomimetic synthesis.

Automated summary

In this study, we investigated the mechanism of the keratin alpha-helix-to-random coil transition and successfully designed and synthesized two-dimensional copper sulfide nanoflakes (CuS NFs) with high absorption in the NIR-II window. The CuS NFs prepared in this way demonstrated outstanding uniformity, size controllability, and biodegradability. Moreover, the CuS NFs in the NIR-II window exhibited excellent photothermal conversion efficiency and extraordinary photoacoustic signal.