Thermogelling chitosan and collagen composite hydrogels initiated with β-glycerophosphate for bone tissue engineering

Abstract

Chitosan and collagen type I are naturally-derived materials used as cell carriers because of their ability to mimic the extracellular environment and direct cell function. In this study beta-glycerophosphate (beta-GP), an osteogenic medium supplement and a weak base, was used to simultaneously initiate gelation of pure chitosan, pure collagen, and chitosan-collagen composite materials at physiological pH and temperature. Adult human bone marrow-derived stem cells (hBMSC) encapsulated in such hydrogels at chitosan/collagen ratios of 100/0, 65/35, 25/75, and 0/100 wt% exhibited high viability at day 1 after encapsulation, but DNA content dropped by about half over 12 days in pure chitosan materials while it increased two-fold in materials containing collagen. Collagen-containing materials compacted more strongly and were significantly stiffer than pure chitosan gels. In monolayer culture, exposure of hBMSC to beta-GP resulted in decreased cell metabolic activity that varied with concentration and exposure time, but washing effectively removed excess beta-GP from hydrogels. The presence of chitosan in materials resulted in higher expression of osterix and bone sialoprotein genes in medium with and without osteogenic supplements. Chitosan also increased alkaline phosphatase activity and calcium deposition in osteogenic medium. Chitosan-collagen composite materials have potential as matrices for cell encapsulation and delivery, or as in situ gel-forming materials for tissue repair.

Fabrication of Cell-Laden Macroporous Biodegradable Hydrogels with Tunable Porosities and Pore Sizes

“…Such DNA decreases in cell-laden hydrogels are consistent with several previous osteogenic studies employing similar OPF hydrogels 36 as well as other systems, including PEG-DA 45,46 and chitosan. 47 These hydrogel constructs share a common characteristic: the absence of cell-attachment sites. Since MSCs are anchorage-dependent progenitor cells, they likely experience cell death due to the lack of extracellular attachment.…”

Biodegradable polymers for dental tissue engineering and regeneration

“…Other applications of collagen relate to reconstructive skin surgery and tissue engineering scaffold for cartilage, tendon, and ligament [311]. In order to improve collagen's potential as a biomaterial it is combined with other degradable polymers [312] or is modified through cross-linking [313], association with bioactive molecules [314], and enzymatic pretreatment [315]. Moreover, composites of HA and collagen are utilized to mimic the composition of natural bone.…”

Sustained knock down of PPARγ and bFGF presentation in collagen hydrogels promote MSC osteogenesis

“…DNA contents were measured using the PicoGreen kit according to manufacturer's instruction. Both ALP activity and calciumcontents were normalized to DNA contents as previously reported [22].…”

“…Serial dilutions of p-nitrophenol (Sigma) were made in Triton solution for plotting standard curve. An OCPC (orthocresolphthalein complex one) method was used to quantify calcium according to the previous report too [3,22]. DNA contents were measured using the PicoGreen kit according to manufacturer's instruction.…”

“…As previously described [22], all frozen samples were pulverized in liquid nitrogen. To assess ALP activity, samples were treated according to the previous report [22]. Briefly, pulverized sample powders were lysed in 0.2% Triton X-100 using two freeze-thaw cycles.…”