Preparation And Properties Of Medical Grade Carbon Microspheres

In recent years,carbon microspheres have been widely used in the fields of medical treatment,catalysis,adsorption,electrochemistry,and synthesis due to their excellent biocompatibility,regular morphology,good chemical stability,and high specific surface area.As a commonly used nonsteroidal anti-inflammatory drug,aspirin shows good in the treatment of rheumatic and cardiovascular and cerebrovascular diseases,but it has great damage to gastric mucosa.Therefore,it is necessary to find suitable drug carriers to reduce the release of drugs in gastric juice and reduce its side effects.The main representative elements of internal radiation therapy,⁹⁰Y and ¹³¹I,have been used in the treatment of liver and thyroid cancer,respectively.Currently,all kinds of microspheres in clinical use have some shortcomings,such as glass microspheres that are easy to deposit in vivo,and the nuclides on resin microspheres that are easy to fall off,while carbon microspheres are good carriers of radionuclides ⁹⁰Y and ¹³¹I due to their high specific surface area,excellent biocompatibility,and regular morphology and structure.In this paper,⁹⁰Y and ¹³¹I were simulated by non-radioactive ⁸⁹Y and ¹²⁷I to study their adsorption mechanism.The main conclusions are shown as follows:（1）Carbon microspheres（CMs）with uniform particle size and good dispersion were prepared by one-step hydrothermal method using sucrose and glutaric acid as raw materials.The maximum drug loading capacity of CMs for acetylsalicylic acid was 228.2mg/g,and the 0.5-hour release rates of carbon microspheres in phosphate buffer salt solution and HCl solution are 36.18%and 17.27%,which comply with the provisions of the Chinese Pharmacopoeia 2020,showing good drug release performance and demonstrating the feasibility of carbon microspheres as drug sustained release carriers.（2）Porous Carbon Microspheres（PCMs）with very high specific surface area（1308.07 m²/g）were successfully prepared by hydrothermal method and modified by chemical activation using sucrose and resorcinol as raw materials.The porous carbon microspheres were loaded with sodium acetylsalicylate and then complexed with Y³⁺.The maximum adsorption capacity of porous carbon microspheres was 5.54 mg/g.The Y³⁺dissolution rate of Y³⁺carbon microspheres in normal saline was less than 0.1%,which reached the dissolution rate requirement of medical radiotherapy grade carrier.（3）Ag/Ag₂O-PCMs were prepared under alkaline conditions with porous carbon microspheres as the carrier and AgNO₃ as the precursor.The specific surface area of Ag/Ag₂O-PCMs was up to 1181.45 m²/g.In the range of pH=1～4,the maximum adsorption capacity of Ag/Ag₂O-PCMs for I^-is 202.65 mg/g.and the adsorption behavior conforms to the pseudo-second-order kinetic model（R²>0.9923）and Langmuir isothermal adsorption model（R²>0.9926）.It has been proved that the adsorption process of Ag/Ag₂O-PCMs for I^-includes both physical adsorption and chemical adsorption.The chemical adsorption is mainly for Ag/Ag₂O nanoparticles bonding with I^-under acidic conditions,among which chemical adsorption plays a dominant role.The I^-dissolution rate of I^--Ag/Ag₂O-PCMs was less than 0.5%.The prepared carbon microspheres are expected to be used as the carrier of ¹³¹I for radiotherapy of thyroid cancer.The carbon microspheres prepared in this paper have high specific surface area,abundant pore structure and uniform particle size,and show excellent performance in drug sustained release and the loading of nuclides of radiotherapy,which provides a new idea and theoretical basis for the practical application of carbon microspheres in the medical field.