Biosynthesis of bimetallic and core-shell nanoparticles: their biomedical applications - a review

Abstract

Recently, researchers succeeded in designing and manufacturing a new class of nanoparticles (NPs) called hybrid NPs. Among hybrid NPs, bimetallic and core-shell NPs were a revolutionary step in NPs science. A large number of green physiochemical and methods for nanostructures synthesis have been published. Eventually, physiochemical methods are either expensive or require the use of chemical compounds for the synthesis of bimetallic and core-shell nanostructures. The main challenges that scientists are facing are making the process cheaper, facile and eco-friendly efficient synthesis process. Green synthesis (biosynthesis) refers to the use of bio-resources (such as bacteria, fungi, plants or their derivatives) for the synthesis of nanostructures. The popularity of the green synthesis of nanostructures is due to their environmental friendliness and no usage of toxic materials, environmental friendliness for the synthesis or stability of nanostructure. Bimetallic and core-shell NPs have many biomedical applications such as removing heavy metals, parasitology, molecular and microbial sensor, gene carrier, single bacterial detection, oligonucleotide detection and so on. The purpose of this study is to discuss briefly the biosynthesised bimetallic and core-shell NPs, their biomedical applications.

Fig. 1

Nano to micro scales

Fig. 2

Structure of core–shell NPs

Fig. 3

Schematic diagram (A–H) and TEM (A″–H″) pictures of different structures of core–shell NPs A, A″: core–shell NPs B, B″: core double‐shell particles or core multi‐shell NPs C, C″: polyhedral core/shell NPs D, D″: core porous‐shell NPs E, E″: hollow‐core shell NPs or single‐shell NPs F, F″: hollow‐core double‐shell NPs G, G″: moveable‐core–shell NPs H, H″: multi‐core–shell NPs M, M″: irregular shape core–shell NPs N, N″: rod core–shell NPs

Fig. 4

Schematic of one‐step, two‐step and multiple‐step synthesis approaches of core–shell NPs

Fig. 5

Schematic diagram (a–f) images of different structures of bimetallic NPs (a) Core–shell NPs (all structures of core–shell NPs such as bimetallic moveable‐core–shell NPs and so on), (b) Random mixed structure bimetallic NPs, (c) Dumbbell structure, (e) Structure with two interfaces, (f) Regular mosaics, (g) Irregular mosaics, (h) Random mixed dendritic structure (sometimes named cluster, star or flower shape structure)

Fig. 6

Schematic for the synthesis of NPs using green tea that led to the synthesis of polyphenol surface coating NPs

Fig. 7

Schematic relationship between nanoscience and others sciences

Fig. 8

Applications of biosynthesised bimetallic and core–shell NPs in biomedical fields