ALCAP

Abstract: Hydroxyapatite (HA), aluminum-calcium-phosphorous oxide (ALCAP), bone meal (BM), and tricalcium phosphate (TCP) ceramic implants are biodegradable and nontoxic to the host. The purpose of this study was to investigate the capability of these ceramics to deliver the catecholamine, epinephrine (EPI) in a sustained and controlled manner. The ceramic powder (less than 38 um particle size) was prepared in our laboratory using standard procedures. Sixteen cylinders were prepared (1 g each) from each of the four ceramic materials. All cylinders were pressed at a compression load of 615 Kg and sintered for 36 hours. ALCAP (group I) and BM (group II) cylinders were sintered at 1400 degrees C and HA (group III) and TCP (group IV) ceramic capsules were sintered at 1150 degrees C. Three capsules from each group were loaded with 30 mg EPI. Capsules containing EPI and control (empty) capsules were each suspended in a serum bottle containing 100 ml of phosphate buffered saline (pH 7.4). The amount of EPI released from each capsule was determined by spectrophotometric methods. Data collected from this study showed that the rate of release of EPI from ALCAP, HA, BM and TCP was 6.14 +/- 0.3 3.55 +/- 0.29, 2.07 +/- 0.26 and 1.17 +/- 0.04 mg/day, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract: The purpose of this investigation was to correlate the thickness of the fibrous capsule and the various histological components surrounding aluminum-calcium phosphate (ALCAP) and tricalcium phosphate (TCP) bioceramics at the subcutaneous (sc) and intraperitoneal (ip) implantation sites. The rational of conducting this investigation is to further elucidate the mechanisms of tissue-implant interaction. Thirteen Sprague-Dawley adult male albino rats were randomly divided into three groups. Animals in groups I and II (n = 5/group) were implanted at both ip and sc implantation sites with either ALCAP or TCP ceramics, respectively. Animals in group III (n = 3) were not implanted and served as the intact control for the comparative purposes. At 90 days postimplantation, the animals in all groups were euthanized (Ketamine/Zylazane) and the fibrous tissue surrounding the ceramic devices was retrieved. After routine histological processing, sections (5 microm) of tissue was stained with hematoxylin and eosin (H&E) and evaluated using light microscopy. With the exception ofneutrophils, at both implantation sites, the fibrous tissues surrounding the TCP bioceramics demonstrated greater capsular thickness, more vascularity, and more macrophages, fibroblasts, and collagen than those surrounding the ALCAP ceramic. Data obtained from this investigation provided further insights into the differences in the tissue-implant responses of calcium-phosphate-based ceramics and the cellular composition of the fibrous tissue reaction found at sc and ip implantation sites.

Abstract: It is well demonstrated in the literature that ceramic drug delivery systems are highly compatible and non-immunogenic. Recent studies in our laboratory have documented the need of an experiment comparing foreign body reactions of several different types of ceramics used for implantation and/or drug delivery. The specific objective of this study was to compare the subcutaneous (s.c.) and intraperitoneal (i.p.) foreign body reactions and biocompatibility of the following implantable materials presently used in orthopedics: ALCAP (aluminum calcium phosphate), HA (hydroxyapatite), and TCP (tricalcium phosphate). The rats were divided into four groups: Group I consisted of 10 rats implanted with ALCAP i.p. and s.c., Group II (n = 10) animals were implanted i.p. and s.c. with HA, Group III consisted of 10 rats implanted i.p. and s.c. with TCP, and Group IV consisted of 10 control animals that were housed under the same environmental conditions as the three experimental groups. At 90 days post-implantation, rats in all four groups were euthanized. The microscopic evaluation of the fibrous tissue surrounding i.p. and s.c. implants revealed the following: 1) all of the ceramic devices had varying degrees of fibrous capsule formation at the time of sacrifice, 2) the thickness of the fibrous tissue capsule was dependent on the type of ceramic used, and 3) the thickness of the fibrous tissue capsules around the subcutaneous devices differed remarkably from implants placed intraperitoneally. The data from this study indicates that capsule formation is dependent upon factors such as ceramic composition and surgical implantation site.

Abstract: Summary It is well documented that several ceramic materials are highly compatible and non-immunogenic with host tissues. Recent studies have demonstrated the need for further investigation of these devices in vivo to further elucidate the possible mechanisms involved in biocompatibility. The purpose of this investigation was to study the morphological characteristics of the fibrous tissue capsule resulting from the implantation of aluminum calcium phosphate (ALCAP) and hydroxyapetite (HA) bioceramics. Implants of ALCAP and HA were implanted into 10 adult male rats subcutaneously (S/C) and intraperitoneally (I/P). At 90 days post-implantation, the animals were euthanized, and the ceramic devices, the fibrous tissue, and vital organs were harvested. Evaluation of routine stained sections (5 m, hematoxylin & eosin) of the fibrous tissue capsule surrounding the HA and ALCAP ceramics revealed the following: 1) all the ceramic devices had fibrous connective tissue capsules of slightly varying degrees of thickness at the time of sacrifice, depending on the site of implantation and type of material, and 2) there were statistically significant differences (p