Silk/Fibroin Microcarriers for Mesenchymal Stem Cell delivery: optimization of cell seeding by the Design of Experiment

Abstract: In this methodological paper, lyophilized fibroin-coated alginate microcarriers (LFAMs)
proposed as mesenchymal stem cells (MSCs) delivery systems and optimal MSCs seeding conditions
for cell adhesion rate and cell arrangement, was defined by a Design of Experiment (DoE) approach.
Cells were co-incubated with microcarriers in a bioreactor for different time intervals and conditions:
variable stirring speed, dynamic culture intermittent or continuous, and different volumes of
cells-LFAMs loaded in the bioreactor. Intermittent dynamic culture resulted as the most determinant
parameter; the volume of LFAMs/cells suspension and the speed used for the dynamic culture
contributed as well, whereas time was a less influencing parameter. The optimized seeding conditions
were: 98 min of incubation time, 12.3 RPM of speed, and 401.5 L volume of cells-LFAMs suspension
cultured with the intermittent dynamic condition. This DoE predicted protocol was then validated
on both human Adipose-derived Stem Cells (hASCs) and human Bone Marrow Stem Cells (hBMSCs),
revealing a good cell adhesion rate on the surface of the carriers. In conclusion, microcarriers can be
used as cell delivery systems at the target site (by injection or arthroscopic technique), to maintain
MSCs and their activity at the injured site for regenerative medicine.