Uniform deposition of protein incorporated mineral layer on three‐dimensional porous polymer scaffolds

Abstract

Inorganic-organic hybrid materials designed to facilitate bone tissue regeneration use a calcium phosphate mineral layer to encourage cell adhesion, proliferation, and osteogenic differentiation. Mineral formed on porous materials is often discontinuous through the thickness of the scaffold. This study aimed to uniformly coat the pores of three-dimensional (3D) porous, polymer scaffolds with a bone-like mineral layer in addition to uniformly incorporating a model protein within this mineral layer. A filtration system designed to induce simulated body fluid flow through the interstices of 3D polylactic-co-glycolic acid scaffolds (10-mm diameter x 2-mm thickness) illustrated that a uniform, continuous mineral layer can be precipitated on the pore surfaces of a 3D porous structure within 5 days. MicroCT analysis showed increased mineral volume percent (MV%) (7.86 +/- 3.25 MV%, p = 0.029) and continuous mineralization of filtered scaffolds compared with two static control groups (floating, 0.16 +/- 0.26 MV% and submerged, 0.20 +/- 0.01 MV%). Furthermore, the system was effective in coprecipitating a model protein, bone sialoprotein (BSA), within the mineral layer. A 10-fold increase in BSA incorporation was seen when coprecipitated filtered scaffolds (1308 +/- 464 microg) were compared to a submerged static control group (139 +/- 45 microg), p < 0.001. Confocal microscopy visually confirmed uniform coprecipitation of BSA throughout the thickness of the filtration scaffolds. The designed system enables 3D mineralization through the thickness of porous materials, and provides the option of including coprecipitated biomolecular cues within the mineral layer. This approach of providing a 3D conductive and osteoinductive environment could be conducive to bone tissue regeneration.

Physicochemical Properties and Applications of Poly(lactic-co-glycolic acid) for Use in Bone Regeneration

“…Moreover, PLGA is most often used in combination other ceramic or polymeric materials that interact with PLGA, thereby enhancing the difficulty to draw unambiguous conclusions on the specific effects of physicochemical characteristics of PLGA on ultimate performance in bone regeneration. In this regard, it is important to notice that relevant information on, for example, polymer molecular weight, [30][31][32][33][34][35] stereochemistry, [31][32][33][34] or end-group functionalization, [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] are often missing, which complicates scientific progress even further.…”

“…85 Several studies describe the use of biomimetic processes to produce apatite-coated PLGA constructs for bone tissue engineering by incubation of polymeric scaffolds in simulated body fluid (SBF) to obtain a mineralized scaffold. [32][33][34]86 The resulting coatings were shown to enhance the osteoconductive properties of PLGA. However, this procedure has drawbacks related to the immersion of the PLGA scaffold in SBF, as the scaffold can undergo hydrolytic degradation on soaking in aqueous solutions.…”

Use of Micro-Computed Tomography to Nondestructively Characterize Biomineral Coatings on Solid Freeform Fabricated Poly (L-Lactic Acid) and Poly (ɛ-Caprolactone) Scaffolds In Vitro and In Vivo

“…14 Although previous studies showed that m-CT may be applicable to monitor in vitro mineralization of porous scaffolds, 19 by m-CT has not been examined. Therefore, to evaluate the accuracy of m-CT data and qualify the amount of mineral, TMC and mineral volume from m-CT data were compared with the amount of calcium in the mineral layers using OCPC method which has been used to characterize biomineral coatings.…”

“…13,14,16 The existence of biomineral coatings on polymer scaffold surfaces also have been examined using m-CT since polymer is almost radio transparent compared to other radio-dense materials. [17][18][19] However, the 3D volume and distribution of mineral coating within porous scaffolds has not been precisely quantified and verified versus destructive methods. Furthermore, changes in mineral coating following implantation in vivo have not been rigorously quantified in 3D.…”

Proteins and Their Peptide Motifs in Acellular Apatite Mineralization of Scaffolds for Tissue Engineering

“…83 However, the incorporated protein could improve the mineral phase by conveying a function such as improvement of degradation kinetics of the polymer substrate 174,175 or adherence or stimulation of bone forming cells 184,185 (see also above paragraphs on drug delivery in the Peptide Coatings section).…”