The aqueous synthesis of pure bismuth
nanoparticles (Bi NPs) is
still challenging due to oxidative decomposition and hydrolytic instability,
especially in aqueous media. This study reports the fabrication of
novel high Bi content biohybrids in the presence of Spirulina platensis (SP) microalgae as biotemplate
for enhanced computed tomography (CT) imaging. Rectangular microrods
coated with a high content of metal Bi NPs were obtained via an one-pot chemical reduction method with minimally involved reagents
in aqueous media, which could be converted to hollow microrod materials
after calcination. The effect of the molar ratio of NaBH4 as a reducing agent and bismuth nitrate on the nature and morphology
of the target biohybrids was fully investigated. Increasing the molar
ratio of NaBH4/Bi led to the conversion of Bi2O3 to metal Bi NPs with the same morphology. The resultant
biohybrid showed high physiological stability, suitable antioxidant
activity, long circulation time, low toxicity, and natural degradability.
Also, hemocompatibility assay revealed minor hemolytic activity of
the final biohybrids. X-ray attenuation measurements and in
vivo animal tests with both oral administration and intravenous
injection of the biohybrid showed high CT contrast efficacy compared
with those of conventional CT contrast agents. In summary, the prepared
biohybrids could serve as a promising CT probe for both a functional
gastrointestinal (GI) tract and intravenous injection.