Thanoo B C, Jayakrishnan A
Polymer Chemistry Division, Biomedical Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India.
J Microencapsul. 1991 Jan-Mar;8(1):95-101. doi: 10.3109/02652049109021863.
Chloroform solutions of medical grade silicone resin were cured in an aqueous dispersion medium containing poly(vinyl alcohol) (PVA) as the drop stabilizer at 40-60 degrees C to generate smooth, spherical, elastic microspheres. The microspheres were encapsulated with tantalum powder to render them radiopaque. Tantalum loaded microspheres having diameter more than 1.00 mm could be prepared by this technique. Incorporation of radiopaques such as barium sulphate and methyl iothalamate resulted in the instability of the suspension giving rise to an agglomerated product. Microspheres were grafted with hydrophilic monomers such as 2-hydroxyethyl methacrylate (HEMA) and N-vinyl pyrrolidone (NVP) using ionizing radiation from a 60Co source in an effort to make their surfaces hydrophilic. While the graft yield was very little when HEMA alone was used for grafting, a combination of HEMA/NVP in a 1:1 ratio produced better graft yields resulting in improved surface hydrophilicity. The tantalum loaded microspheres were found to be very resistant to surface modification. Microspheres could be dispersed in water with the aid of small quantities of surfactants such as Tween 20. These microspheres may find use in particulate embolization.
医用级硅树脂的氯仿溶液在含有聚乙烯醇（PVA）作为液滴稳定剂的水分散介质中于40 - 60摄氏度固化，以生成光滑、球形、有弹性的微球。这些微球用钽粉包裹，使其具有射线不透性。通过该技术可以制备直径大于1.00毫米的载钽微球。加入硫酸钡和碘他拉酸甲酯等射线不透性物质会导致悬浮液不稳定，产生团聚产物。使用来自60Co源的电离辐射，将微球与甲基丙烯酸2 - 羟乙酯（HEMA）和N - 乙烯基吡咯烷酮（NVP）等亲水性单体接枝，以使它们的表面具有亲水性。单独使用HEMA进行接枝时接枝产率很低，而以1:1比例混合的HEMA/NVP产生了更好的接枝产率，从而改善了表面亲水性。发现载钽微球对表面改性具有很强的抗性。借助少量表面活性剂如吐温20，微球可以分散在水中。这些微球可能用于颗粒栓塞。
