Nanomaterials are materials in which at least one of the dimensions of the particles is 100 nm and below. There are many types of nanomaterials

but noble metal nanoparticles are of interest due to their uniquely large surface-to-volume ratio

high surface area

optical and electronic properties

high stability

easy synthesis

and tunable surface functionalization. More importantly

noble metal nanoparticles are known to have excellent compatibility with bio-materials

which is why they are widely used in biological applications. The synthesis method of noble metal nanoparticles conventionally involves the reduction of the noble metal salt precursor by toxic reaction agents such as NaBH

4

hydrazine

and formaldehyde. This is a major drawback for researchers involved in biological application researches. Hence

the bio-synthesis of noble metal nanoparticles (NPs) by bio-materials via bio-reduction provides an alternative method to synthesize noble metal nanoparticles which are potentially non-toxic and safer for biological application. In this review

the bio-synthesis of noble metal nanoparticle including gold nanoparticle (AuNPs)

silver nanoparticle (AgNPs)

platinum nanoparticle (PtNPs)

and palladium

nanoparticle (PdNPs) are first discussed. This is followed by a discussion of these biosynthesized noble metal in biological applications including antimicrobial

wound healing

anticancer drug

and bioimaging. Based on these

it can be concluded that the study on bio-synthesized noble metal nanoparticles will expand further involving bio-reduction by unexplored bio-materials. However

many questions remain on the feasibility of bio-synthesized noble metal nanoparticles to replace existing methods on various biological applications. Nevertheless

the current development of the biological application by bio-synthesized noble metal NPs is still intensively ongoing

and will eventually reach the goal of full commercialization.