However, after 48 h culture, number of cells proliferated on all sericin films was not significantly
different. This indicated that L929 cells had different proliferation rate when cultured on different
types of sericin films, as confirmed by PDT. The PDT of cells proliferated on urea extracted sericin
film (27 h) was similar to that on heat extracted sericin film (29 h). Furthermore, cells proliferated
on both pure heat and urea extracted sericin films showed significantly lower PDT than those
proliferated on the blended F/S films. This suggested that sericin extracted by urea treatment could
enhance cell proliferation rate which may be due to the suitability of its polypeptide chains.