Bi₂S₃-based Nanoprobe For Cancer Diagnosis And Therapy

At present,with the rapid development of nanotechnology,nanomaterials play an important role in the field of biomedicine,which provides new ideas and methods for the diagnosis and therapy of cancer.On the one hand,due to the fact that nanomaterials are easy to be functionalized,some nanomaterials have been widely introduced into molecular imaging to increase imaging resolution or sensitivity and enable early diagnosis of cancer.These nanomaterials are very suitable for the construction of novel therapeutic agents such as photothermal agents,chemotherapeutic agents and immunological agents because of the advantages of the small size,low toxicity and side effects.Nanometer diagnosis and therapeutic agents aim to integrate high-sensitivity medical diagnosis and effective therapy to achieve the best therapeutic effect.In recent years,it has attracted more and more researchers in this field.In most previous studies,several kinds of nanomaterials were introduced into the same nanoplatform to enhance its versatility.This undoubtedly increases synthesis steps,time,and potential toxicity.In the clinical diagnosis of cancer,X-rays can image the entire human body,which is one of the most important imaging tools in current diagnostics.However,the shortcomings such as the low sensitivity and the short circulation time in the body of the iodine-based small molecule CT imaging contrast agent used in clinic make it difficult to be used for the early diagnosis of cancer.In order to obtain valuable imaging results in actual use,a large dose of contrast agent is required,which easily causes side effects of kidney toxicity.Meanwhile,the iodine micromolecule CT contrast agent also has limitations such as being difficult to modify and having a short circulation time in the body,leading to its inability to be concentrated in the lesion tissue and difficult to be used for long-term,dynamic monitoring of the disease.Based on the above scientific issues,we conducted the following study:Bismuth has an atomic number of 87,so theoretically it has a stronger X-ray absorptivity than Iodine.Futhurmore,unlike most other heavy metal elements,Bi compounds have good biocompatibility.Taking the aforementioned into consideration,we proposed a strategy using Bi as a contrast unit and built Bi-type nano-CT probes.At the same time,the synthesis of nano-Bi probes faces scientific problems such as difficult control of particle size and hardly can achieve a large-scale preparation.We have achieved large-scale,controllable synthesis of CT probes with ultra-small Bi₂S₃nanoprobes（2-3 nm）by controlling nano-nucleating and growth rates.This Bi-type nano-CT probe not only has better imaging effect than the iodine small-molecule CT contrast agent used in clinical use,but also has an in vivo circulation half-life of more than 2 hours,which is much longer than iodine small-molecule CT contrast agents（1minute）.This long-term internal circulation feature allows the probe to be efficiently enriched in relevant organs and lesions,enabling imaging analysis of internal organs and lesions.Moreover,bismuth sulfide has a narrow energy bandgap and strong absorption in the near-infrared light（NIR）region,which can efficiently convert the absorbed light energy into heat energy.Therefore,the Bi₂S₃ nanoprobe provides an ideal platform for CT-guided tumor photothermal therapy（PTT）.The results of in vivo experiments showed that the Bi₂S₃ nanoprobe can be effectively enriched in the tumor site to achieve CT imaging of cancer,and under the irradiation of NIR,the nanoprobe achieved CT-guided cancer therapy,and its tumor elimination rate reached100%.In addition,the ultra-small Bi₂S₃ nanoprobe can be rapidly excreted after performing its function,thereby reducing the toxic side effects on the body.The ultra-small nanoprobe integrated with diagnosis and therapy we constructed provides a new idea for solving the toxic and side effects produced by traditional cancer diagnosis and therapy.