Apatite as carrier for growth hormone:In vitro characterization of loading and release

Abstract

Previous studies concerning bone drug delivery systems have provided little data about the amount of drug loaded, one of the essential factors for determining the dose/effect relationship. To investigate this factor, an adsorption method involving a therapeutic agent was tested in vitro on an apatitic calcium phosphate (AP). One milligram of human growth hormone (hGH) was deposited onto 0.1, 0.15, and 0.2 g of AP powder over a period of 24 h at 37 degrees C. The amount of hGH loaded was determined by subtracting the dose recovered from that applied on AP. The results show that 1 g of AP absorbed 9.48 mg of hGH. From 0.1 and 0.15 g of hGH-loaded AP, hGH was released in vitro for 2 and 3 weeks, respectively, with a 50% time release (T1/2) at 30 h and 72 h, respectively, for the two quantities. The amount of drug loaded and the determined release kinetics were compatible with the action pattern of hGH, indicating that hGH-loaded calcium phosphate supports are suitable for bone-growth promotion.

Calcium phosphate-alginate microspheres as enzyme delivery matrices

“…The possibility of exploiting the capacity of both components to act as enzyme delivery systems was investigated, since both may immobilise proteins [23][24][25][26][27]. For this reason, the enzyme was incorporated into the ceramic-alginate matrix before gel formation in two different ways, as described before.…”

“…Furthermore, recent in vivo studies showed direct bone contact of implanted cylinders containing calcium titanium phosphate as the main phase [24]. HAp, which has long been recognised for its bioactivity and osteoconductive properties and has been extensively tested as matrix in drug delivery applications [25,26], was also used in the present investigation.…”

Sol–Gel Preparation and Properties of Fluoride‐Substituted Hydroxyapatite Powders

“…H YDROXYAPATITE (HA, Ca 10 (PO 4 ) 6 (OH) 2 ) has attracted much interest as an implant material for teeth and bones, due to the similarity of its crystallography and chemical composition to that of human hard tissues. 1,2 Currently, the HA ceramic is used as a bone filler to heal and regenerate new tissues within the defect sites, in the form of powders, granules, and small porous blocks.…”

“…7 On the other hand, pure fluorapatite (FA, Ca 10 (PO 4 ) 6 F 2 ) is known to have a much lower solubility than HA, because FA possesses a greater stability than HA, both chemically and structurally. 8,9 Moreover, the FA forms fluor-hydroxyapatite (FHA, Ca 10 (PO 4 ) 6 (OH,F) 2 ) solid solutions with HA through the replacement of OH Ϫ by F Ϫ . Hence, modulation of the extent of fluoride substitution provides an effective way of controlling the solubility of the apatite.…”

Amelioration of Anemia in the ICGN Mouse, a Renal Anemia Model, with a Subcutaneous Bolus Injection of Erythropoietin Adsorbed to Hydroxyapatite Matrix

“…Advantages of this skintargeted approach include the fact that HAp administration is minimally invasive and have neither cellular nor humoral immune response. HAp particles have been examined as a carrier for sustained release of various therapeutic agents, such as antibiotics [2,13,28,29], anticancer drugs [11,33], and proteins [6,8,18,21]. It is known that the protein adsorbed to HAp is difficult to release in vitro, because the protein adsorbed to HAp is released with biodegradation of HAp [24].…”