High-Performance Spirulina–Bismuth Biohybrids for Enhanced Computed Tomography Imaging

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.