Biomimetic apatite formation on poly(lactic acid) composites containing calcium carbonates

Abstract

Poly(lactic acid) composites containing a mixture of calcium carbonates (vaterite, aragonite, and calcite) were prepared by a carbonation process in methanol. Soaking of the composites for 3 h in simulated body fluid (SBF) at 37°C resulted in the deposition of bonelike apatite particles on the composite surface. After soaking the composites, vaterite phase in the composites was forward to dissolve rapidly, resulting in increase the supersaturation of the apatite in SBF. 13 C cross-polarization magic angle spinning nuclear magnetic resonance ( 13 C CP/MAS-NMR) spectra of the composites suggested the formation of a bond between Ca 2+ ion and the COO − group, which induces the apatite nucleation. These results may elucidate the mechanism of means to reduce the induction period for apatite formation.Artificial materials are generally encapsulated by a fibrous tissue to be isolated from the surrounding bones when implanted into the bone defects. However, a kind of ceramics and glasses such as hydroxyapatite ceramics or Bioglass bond directly to living bone without forming the fibrous tissue and they are often called bioactive materials. They form a carbonate-containing hydroxyapatite layer on their surface in the living body and bond to living bone through apatite layers. 1,3 This layer is very similar to the apatite in the bone in its composition and structure (bonelike apatite). 4 The apatite can be formed biomimetically on bioactive materials even in simulated body fluid (SBF), which is a buffer solution with inorganic ion concentrations nearly equal to those of human blood plasma. 5 Two indispensable conditions needed for the formation of bonelike apatite on materials are (i) the existence of the surface functional groups that induce nucleation of the apatite and (ii) the supersaturation of the apatite in body fluid or SBF should be increased. [5][6][7] Materials having a high bioactivity or biodegradability play an important role in the recovery of the part of bone defects. In this work, highly bioactive bone-filler materials were prepared for bone substitution at an early stage after clinical operation. Biodegradable poly(lactic acid) (PLA), because of many carboxy groups, is one of the promising candidates for supplying inducers for the bonelike apatite nucleation. A carboxy group is known to induce apatite nucleation 6 and can be formed by hydrolyzation of PLA. To increase the supersaturation of apatite in body fluid or SBF, a large amount of Ca 2+ ions should be dissolved from the materials. Formation of apatite having lattice constant and Ca/P atomic ratio close to those of natural bone has been reported to influence carbonate ions in the solution. 8 From this point of view, calcium carbonate is expected to supply both Ca 2+ and carbonate ions simultaneously into body fluid or SBF resulting in increase in the supersaturation of the apatite.It is well-known that calcium carbonate has three polymorphs, viz., calcite, aragonite, and vaterite. Solubility of vaterite is higher than that of calcite or aragonite. 9...

Surface functional group dependent apatite formation on bacterial cellulose microfibrils network in a simulated body fluid

“…Formation of bonelike apatite layer on the surface of the artificial material is thus required for its ability to bond with the living bone without intervention of the fibrous tissue when it is used as a bone repairing material. 3 On this basis, extensive research has been explored on formation of bonelike apatite on various bioactive materials including NaOH and heat treated titanium and tantalum metals 4,5 and organic polymers [6][7][8] by means of biomimetic approach. This method consists of soaking bioactive materials in a simulated body fluid, SBF, with ion concentrations nearly equal to those of human blood plasma at physiological pH and temperature and analyzing the evolution of apatite formation with time.…”

Effect of preparation route on the degradation behavior and ion releasability of siloxane-poly(lactic acid)-vaterite hybrid nonwoven fabrics for guided bone regeneration

“…The peaks at approximately 170 ppm are related to the carboxy groups. It has been reported that when a bivalent ion is coordinated with a carboxy groups, a new peak corresponding to that groups appears at the side of low magnetic field in the band 17) , and that, on the composites prepared from PLA and vaterite, a peak indicating the coordination between Ca 2+ ions originating from vaterite and the carboxy groups originating from PLA appears at approximately 172 ppm 18) . In this work, to identify the existence of the peak at approximately 172 ppm, each broad peak at approximately 170 ppm was deconvoluted into two peaks by using a 2-component Gaussian fitting method.…”

Bonelike Apatite Coating on Skeleton of Poly(lactic acid) Composite Sponge

“…To eliminate this risk, it has been reported that the composites were fabricated using the polymer sponge coated with bioactive materials such as hydroxyapatite or Bioglass. [7][8][9] We reported earlier that a compact of calcium carbonate (vaterite)/poly(lactic acid) composite (CCPC) was reported to form b-HA on its surface even after 3 hours of soaking in SBF at 37 C. 10) The rapid formation of the b-HA was suggested to originate from the integration of PLA having carboxy groups bonded with Ca 2þ ions for b-HA nucleation and a large amount of calcium carbonate (vaterite) having an ability to effectively increase the supersaturation of b-HA due to the fast dissolution of the nano-sized vaterite. We believe that various novel biomaterials can be prepared using CCPC.…”