Advances in bovine serum albumin-protected gold nanoclusters: from understanding the formation mechanisms to biological applications

Fluorescent gold nanoclusters (Au NCs) have become a promising material in nanobiotechnology due to their smaller size, fluorescence properties, and biocompatibility. Among these, proteins, mainly bovine serum albumin (BSA)-protected Au NCs, have been used extensively for diverse biological applications. The current literature data from the web of science suggest more than 2,400 publications are reported till July 2022, suggesting the pioneered role of the BSA–Au NCs in different biological applications. Even though numerous reviews and perspectives are written on fluorescence Au NCs (including protein protected), biological applications of Au NCs, and so on, still, to the best of our knowledge, none of them so far are focused on BSA–Au NCs. In this review, we highlighted the BSA-protected Au NCs starting from their synthesis, structural analysis, and biological applications. Briefly, we summarize various ‘top-down’ and ‘bottom-up’ synthesis approaches of fluorescent BSA–Au NCs. Then, we present the characterization techniques employed to study the intrinsic and unique properties of BSA–Au NCs. The probable synthesis mechanisms are also explored. Furthermore, we discuss the biological applications of fluorescent BSA–Au NCs, with a major focus on bioimaging, biosensing, biocatalysis, and drug delivery. Finally, current challenges and future potential prospective of fluorescent BSA–Au NCs in controllable synthesis and biological research are briefly discussed.