hydroxyapatite/poly-L-lactide Research Articles

Endosteal strut using a hydroxyapatite/poly-L-lactide mesh tube with a proximal humeral locking plate for the treatment of proximal humeral fractures.

Proximal humeral fractures cause large intramedullary bone defects after humeral-head reduction. Hydroxyapatite/poly-L-lactide (HA/PLLA) materials are widely used for various fractures. However, the efficacy of endosteal strut using a HA/PLLA mesh tube (ES-HA/PLLA) with a locking plate for treating proximal humeral fractures was not reported. The purpose of this study is to examine the efficacy of ES-HA/PLLA with a proximal humeral locking plate in proximal humeral fractures. Seventeen patients with proximal humeral fractures treated using ES-HA/PLLA with a locking plate from November 2017 to November 2021 were evaluated. The range of motion of the shoulder and postoperative complications were assessed at the final follow-up. Radiographs were evaluated to assess bone union and loss of reduction by measuring humeral-head height (HHH) and humeral neck-shaft angle (NSA). The average flexion and external rotation of the shoulder at the final follow-up were 137° (range, 90-180°) and 39° (range, - 10 to 60°), respectively. All fractures were united. The average HHH and NSA just after the surgery and final follow-up were 12.5mm and 11.6mm and 129.9° and 127.4°, respectively. Two patients presented screw perforation of the humeral head. One patient underwent implant removal due to infection. Avascular necrosis of the humeral head was observed in one patient with arthritis mutilans. The use of ES-HA/PLLA with a proximal humeral locking plate resulted in bone union in all patients and prevented postoperative loss of reduction. ES-HA/PLLA is one of the treatment options for proximal humeral fractures.

Biomechanical integrity of hydroxyapatite/poly-l-lactide fixation system in mandibular body reconstruction with deep circumflex iliac artery free flap

The mechanical integrity of a deep circumflex iliac artery (DCIA) free flap connected to the remaining mandible after a segmental mandibulectomy directly influences the reconstructive surgery prognosis. This study aimed to assess the biomechanical integrity of fixation systems on the reconstruction site. The mechanical properties of mini-plate and screw fixations in two different materials, namely titanium (Ti) and hydroxyapatite/poly-L-lactide (HA-PLLA), were simulated using finite element analysis. Each end of the free flap was fixed with three mini-plates, a total of six mini-plates at the midline and the anterior to the coronoid process with 35 screws. The masticatory loading increment effect on peak von Mises stress (PVMS) distribution, size of fixation deformation, principal stresses on bones, and a gap opening size were taken into account for each material's pros and cons evaluation. Based on the comprehensive evaluation, the Ti fixation system presented superior performance immediately after surgery. However, the Ti fixation system's superiority was diminishing over time, and eventually, the differences became marginal at 12-months postop. This study's results imply the clinical indications of the HA-PLLA fixation system with the DCIA free flap during mandibular reconstructive surgery.

Biomechanical evaluation of unilateral subcondylar fracture of the mandible on the varying materials: A finite element analysis.

Fixation materials used in the surgical treatment of subcondylar fractures contribute to successful clinical outcomes. In this study, we simulated the mechanical properties of four fixation materials [titanium (Ti), magnesium alloy (Mg alloy), poly-L-lactic acid (PLLA), and hydroxyapatite/poly-L-lactide (HA-PLLA)] in a finite-element analysis model of subcondylar fracture. Two four-hole plates were fixed on the anterior and posterior surfaces of the subcondyle of the mandible. In the simulation model of a subcondylar fracture, we evaluated the stress distribution and mechanical deformation of fixation materials. The stress distribution conspicuously appeared on the condylar neck of the non-fractured side and the center of the anterior plate for all materials. More stress distribution to the biologic component appeared with HA-PLLA than with Ti or Mg alloy, but its effects were less prominent than that of PLLA. The largest deformation was observed with PLLA, followed by HA-PLLA, Mg alloy, and Ti. The results of the present study imply the clinical potential of the HA-PLLA fixation material for open reduction of subcondylar fractures.

Intramedullary fixation with bioabsorbable and osteoconductive hydroxyapatite/poly-L-lactide threaded pin in digital replantation

In digital replantation, Kirschner wire (K-wire) fixation has commonly been used for osteosynthesis. On the other hand, K-wires are often obtrusive because of protrusion from the replanted digit. We describe a case series treated using hydroxyapatite/poly-L-lactide (HPLLA) threaded pins, which are not only bioabsorbable, but also osteoconductive, for osteosynthesis in crushed amputation or comminuted fracture, including distal phalanx amputation. Using an HPLLA threaded pin, 10 digital replantations were performed between July 2016 and April 2018. The precisely cut pin is manually pushed into the fracture site as an intramedullary nail. The pin is first pushed into the distal site, and then into the proximal site, after drilling with a K-wire of the same diameter as the pin. All amputations were crush type, and levels of amputations were Tamai zone I in three cases, zone II in two and zone III in five. Eight of the 10 digits survived. The two digits that did not survive showed venous insufficiency. Bone union of the eight digits was successfully obtained after 9–19 weeks (median 12 weeks). No adverse events occurred such as distortion of the pin, infection or foreign body reaction. The HPLLA threaded pin may be an adequate device to fix fractures in digital replantation.

The influence of the preparation conditions and filler content on thermal properties of poly-l -lactide and hydroxyapatite/poly-l -lactide nanocomposite

Poly-l-lactide (PLLA) and hydroxyapatite/poly-l-lactide (HAp/PLLA) are two widely used biomaterials for three-dimensional scaffolds, drug release matrices and implantable medical devices for reparation of bone tissue; diversity in the initial preparation and filler content has a significant influence on different properties such as morphology and crystallinity, thus playing a considerable role in most of these applications. For this reason, PLLA and HAp/PLLA samples with a large difference in crystallinity (from below 20% to over 70%) and filler content (up to 86 wt% of HAp nanoparticles with an average diameter of 80 nm) were prepared and consequent dissimilarities in morphology, crystallinity and thermal properties were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) measurements and Fourier transform infrared (FTIR) spectroscopy. Special attention was devoted to analyzing data obtained from thermal measurements. A three-phase model was employed in order to describe the heat capacity step decline in the nanocomposite; the evolution in different polymer fractions, the crystalline fraction and the mobile and rigid amorphous fractions, with filler content was determined. © 2017 Society of Chemical Industry

Hydroxyapatite/poly-l-lactide nanocomposites coating improves the adherence and proliferation of human bone mesenchymal stem cells on porous biphasic calcium phosphate scaffolds

A well-developed three-dimensional (3-D) biphasic calcium phosphate (BCP) scaffold with interconnectivity and high porosity was fabricated for bone tissue engineering. After being coated with hydroxyapatite/poly-l-lactide (HA/PLLA) nanocomposites, the scaffold maintained the framework structure, and the porous network structure of scaffolds remained unchanged. MTT assay showed significantly increased proliferation of human bone mesenchymal stem cells (hBMSCs) on coated BCP scaffolds compared with uncoated scaffolds 5 days after seeding (p<0.05). Under scanning electron microscopy, hBMSCs on the coated BCP scaffolds showed more spreading on the first day after seeding. Furthermore, flocculent mineral accretions were formed on the surface of HA/PLLA coating. Cell adherence and proliferation ability of hBMSCs on scaffolds were improved by coating with HA/PLLA nanocomposites.

Application of custom-made bioresorbable raw particulate hydroxyapatite/poly-l-lactide mesh tray with particulate cellular bone and marrow and platelet-rich plasma for a mandibular defect: Evaluation of tray fit and bone quality in a dog model

The purpose of this study was to evaluate tray fit and bone quality of particulate cancellous bone and marrow (PCBM) mandibular reconstruction using custom-made bioresorbable forged composites of a raw particulate hydroxyapatite/poly-l-lactide (HA/PLLA) tray in a dog model. Mesh sheets of HA/PLLA were formed in a tray shape according to the mandible stereolithographs of 14 beagle dogs. Platelet-rich plasma (PRP) was obtained from venous blood, and PCBM was harvested from the iliac crest. Bone defects were made bilaterally on the lower borders of the mandible. The PCBM and PRP were mixed and compressed into the defects and a custom-made HA/PLLA or a manually adopted titanium tray was fixed by screws. Tray fit and bone qualities were evaluated using computed tomography, microfocus computed tomography and confocal laser scanning microscopy. In buccal side, there is no significant difference with tray fit between the HA/PLLA and the titanium type, but in lingual side, it was better in the HA/PLLA type than that of the Ti type. Bone volume fraction (BV/TV) had markedly increased on the HA/PLLA side at 12 months. In conclusion, the custom-made HA/PLLA tray was easily and accurately adapted to the mandible, and had achieved sufficient bone quality by 12 months.

INTERACTION OF BIOMATERIALS CONTAINING CALCIUM HYDROXYAPATITE/POLY-L-LACTIDE WITH THE SIMULATED BODY FLUID

The purpose of biomaterials is to replace a part or a function of the body in a safe, physiologically and economically acceptable way. The process of the reconstruction of bone defects has always been a big problem in orthopedics and maxillofacial surgery. Since hydroxyapatite (HAp) was detected as a component, the predominant constituent and the integral element of Mammalian bones, the development of the phospate ceramics as potential materials for implantation was enabled. This study investigated whether and in which way biomaterial calcium hydroxyapatite/poly-L-lactide (HAp/PLLA) interacts with the ionic composition of the human plasma. The simulated body fluid (SBF) is an artificial fluid that has the ionic composition and ionic concentration similar to the human blood plasma. HAp/PLLA was incubated for 1, 2, 3 and 5 weeks in SBF. The surfaces of both treated and untreated materials were analyzed on a scanning electron microscopy (SEM), and were also exposed to the energy dispersive X-ray spectroscopy (EDS), while SBF was submitted to the measuring of pH and electrical conductivity. However, our results indicate that the degradational changes of the material HAp/PLLA in SBF start from the surface of the treated material and that observed changes are the consequence of dissolution of its polymer component and the precipitation of the material similar to hydroxyapatite on its surface. This material shows good characteristics that place it among good candidates for the application in orthopedics and maxillofacial surgery. Acta Medica Medianae 2011;50(4):35-39.

The influence of gamma radiation on the molecular weight and glass transition of PLLA and HAp/PLLA nanocomposite

The influence of gamma radiation on the molecular weight and glass transition behaviour of poly- l-lactide (PLLA) and hydroxyapatite/poly- l-lactide (HAp/PLLA) nanocomposite has been studied. Since PLLA exposed to high-energy radiation in the presence of air is prone to chain scission reactions and large degradation, changes in molecular weight were obtained by gel permeation chromatography (GPC). Alterations in the glass transition behaviour were investigated by differential scanning calorimetry (DSC). The apparent activation energy (Δ H∗) for glass transition was determined on the basis of the heating rate dependence of the glass transition temperature ( T g ). Our findings support the fact that chain scission is the main reason for the decrease of T g and Δ H∗ with the absorbed dose. Furthermore, more intensive chain scission degradation of PLLA was observed in HAp/PLLA and can only be ascribed to the presence of HAp nanoparticles. Consequently, initial differences in the glass transition temperature and/or apparent activation energy of PLLA and HAp/PLLA became more pronounced with absorbed dose. This study reveals that radiation-induced changes in molecular weight and glass transition temperature occur in a predictable and fairly accurate manner. Therefore, gamma radiation can be used not only for sterilization but also for tailoring desirable end-use properties of these biomaterials.

The Influence of Gamma Radiation on the Glass Transition of Hydroxyapatite/Poly L-Lactide Composite

Hydroxyapatite/poly L-lactide (HAp/PLLA) is a composite biomaterial which has been widely utilized for substitution and reparation of the hard bone tissue. It is well known that gamma irradiation has been successfully employed in the modification/sterilization of such porous composites and that it has advantages over other procedures. In this study, differential scanning calorimetry (DSC) measurements were made to investigate the influence of the radiation on glass transition behavior and structural relaxation, as well as to estimate the activation energy for this process. The apparent activation energy ΔH* for structural relaxation in the glass transition region was determined on the basis of the heating rate dependence of the glass transition temperature Tg. Furthermore, the results were correlated with those obtained by gel permeation chromatography (GPC). Our findings support the fact that the radiation-induced chain scission in the PLLA phase is the main reason for the decrease of the glass transition temperature and/or activation energy with the absorbed dose.

Micromechanical properties of a hydroxyapatite/poly- l-lactide biocomposite using nanoindentation and modulus mapping

Biocomposites with ceramic fillers and polymer matrix are becoming attractive materials for bone tissue replacements. Nanoindentation has been used to locally characterize the surface mechanical properties of the hydroxyapatite/poly- l-lactide (HAp/PLLA) biocomposite. Additionally, differences in the mechanical properties of HAp phase were successfully characterized as a function of surface morphology by using a high-resolution modulus mapping technique. HAp granules consist of agglomerates of grainy clusters. Mechanical properties of ceramic grains and PLLA are in fair agreement with literature data. High-resolution methods were able to measure the properties of boundary phases between grains and the pore regions between particles in the agglomerate. After short-time immersion in distilled water, material surface showed a large decrease in storage modulus.

Radiation-induced degradation of hydroxyapatite/poly L-lactide composite biomaterial

The effects of gamma irradiation on the structure and properties of hydroxyapatite/poly L-lactide (HAp/PLLA) biomaterial have been investigated. Effects of radiation on microstructure, degradation of polymer part and thermal stability of composite were determined by scanning electronic microscopy (SEM), gel permeation chromatography (GPC) and thermogravimetric analysis (TGA), respectively. Mechanical properties were obtained through mechanical strength and elasticity modulus. Presented results show that properties of HAp/PLLA decay with irradiation dose, but for doses required for sterilization, changes and damaging effects are acceptable.

Repair of Bone Tissue Affected by Osteoporosis with Hydroxyapatite-Poly-L-lactide (HAp-PLLA) With and Without Blood Plasma

The aim of this study is to examine the reparatory ability of the synthetic biomaterial hydroxyapatite-poly-L-lactide (HAp-PLLA), the replacement of alveolar ridge, and rehabilitation of bone defects caused by osteoporosis, in an experimental group of animals. The experiments are performed on syngeneic Sprague Dawley rats. Osteoporosis is induced by glucocorticoids in rats during a 12-week period. After this, the experimental group of animals is divided into five subgroups. An artificial defect is made in the alveolar bone on the left side of the mandible. In one group of animals, the defect is left to heal by itself, while in other groups, pure HAp-PLLA or one mixed with plasma is implanted. The best results are achieved by the implantation of the HAp-PLLA composite biomaterial mixed with autologous plasma. Formation of a new mandibular bone is seen, growing intensely, leading to rapid osteogenesis.

Synthesis and application of hydroxyapatite/polylactide composite biomaterial

Hydroxyapatite/bioresorbable-polymer composite biomaterials can be used for the bone tissue reconstruction. There are different methods to obtain hydroxyapatite/poly-l-lactide (HAp/PLLA) composite biomaterial, but up to now only hot pressing and forging have been successfully used to produce blocks with mechanical properties similar to the natural bone tissue. By dissolving PLLA polymer mixed with HAp, highly porous HAp/PLLA composite biomaterial was obtained. A wide spectrum of blocks with different properties was produced by hot pressing, varying the pressing parameters. HAp/PLLA blocks were implanted into mice (intraperitoneally) and after implantation, the phenomenon was studied histopathologically and by FT-IR spectroscopy. The obtained composite biomaterial blocks have a compressive strength of up to 140MPa and elasticity module of up to 10GPa. After implantation, good adhesion of the surrounding tissue on the surface of the implant as well as its integration indicate high degree of its biocompatibility.

Evaluation of hot-pressed hydroxyapatite/poly-L-lactide composite biomaterial characteristics.

Hydroxyapatite/poly-L-lactide (HAp/PLLA) is a ceramic/polymer composite, whose application as a resorbable biomaterial for the substitution and repair of hard bone tissue is widely promising in orthopedic, oral, maxillofacial, and reconstructive surgery. Hot processing is a necessary step for obtaining HAp/PLLA composite blocks with mechanical properties similar to those of bones. In this article, the changes in structure and physicochemical properties of HAp/PLLA composite, hot pressed for different pressing times (5, 15, 30, 45, and 60 min), were studied. Because the morphology of HAp/PLLA composite biomaterial is very sensitive to this procedure, its surface microstructure was analyzed by scanning electron microscopy (SEM) coupled with an energy-dispersive X-ray (EDX) detector system. Structural changes occurring in the material, mostly changes in crystallinity of PLLA, were studied by wide-angle X-ray structural analyses (WAXS) and infrared (FTIR) spectroscopy. Using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC), the influence of hot pressing on the properties, crystallization kinetics, and decomposition of HAp/PLLA composite biomaterial was analyzed.

Molecular spectroscopy analysis of the substitution of bone tissue by HAp/PLLA composite biomaterial

Due to its pronounced osteoinductive properties, calcium hydroxyapatite (HAp) has been widely used in medicine. Bioresorptive poly-L-lactide (PLLA) as a polymer biomaterial has been also used extensively in medicine for its non-toxicity and biocompatibility. To combine the advantages exhibited by each of these materials, a HAp/PLLA composite biomaterial has been synthesized and used for reconstruction and repair of bone defects. Hydroxyapatite/poly-L-lactide (HAp/PLLA) composite biomaterial with PLLA of 50,000 and 430,000 g/mole molecular weight was studiedin vivo. The biocomposite with PLLA of both molecular weights was implanted into mice, then removed from their organisms and analyzed by the Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and histopathologic analysis. Characteristic absorption bands, registered and defined by FT-IR spectroscopy, confirm the formation of new functional groups and compounds during the bone repair process using HAp/PLLA biocomposite with PLLA of 50,000 and 430,000 molecular weights. Analysis of the microstructures of the sample surfaces by scanning electron microscopy (SEM) before and after implantation revealed bioresorption of the PLLA polymer phase in the system with PLLA of lower molecular weight and generation of collagen fibers at the sites of implanted bioresorptive PLLA. As the studied synthetic materials behave as the natural bone, i.e., they are phagocytosed and resorpable, they can be considered as biocompatible.

Gamma irradiation processing of hydroxyapatite/poly-L-lactide composite biomaterial

Effects of gamma irradiation on structure and physicochemical properties of the hydroxyapatite/poly-L-lactide (HAp/PLLA) composite were studied in this paper. Since the morphology of HAp/PLLA is very sensitive to gamma irradiation, surface microstructure was analyzed by scanning electron microscopy. Structural changes occurring in the material, mostly changes in PLLA which is more sensitive to irradiation than HAp, were studied by wide angle X-ray structural analyses and infrared spectroscopy. Differential scanning calorimetry measurements were used to study the changes in thermal behavior and crystallinity. Conclusions derived according to different methods were compared.

Structure and characteristics of the hot pressed hydroxyapatite/poly-L-lactide composite

Hydroxyapatite/poly-L-lactide (HAp/PLL) composite biomaterial can be obtained by different processing methods. Three-dimensional blocks of HAp/PLLA composite biomaterial with mechanical characteristics close to the natural bone tissue can be obtained by hot pressing procedure. Effects of synthesis and compacting on the structure and characteristics of the HAp/PLLA composite biomaterial were studied in this work. Using wade angle X-ray structural analyses (WAXS), differentially scanning calorimetry (DSC), thermogravimetric analysis (TGA) and infrared (IR) spectroscopy, the changes occurring in the material during synthesis and hot pressing were monitored. Surface microstructure was analyzed by scanning electronic microscopy (SEM) coupled with electron-dispersion analysis (EDX). The results obtained indicate a possible decrease in the degree of crystallinity with hot pressing time increase. A block of HAp/PLLA composite biomaterial with 1.6 times lower crystallinity of the polymer phase was obtained by hot pressing in a given time interval with a maximum of 60 minutes. Results of TG analysis show that PLLA stability decreases with increasing hot pressing time, and vice versa. IR study proved that neither destructive changes in constituents nor formation of new phases occurred during hot pressing.

A study of HAp/PLLA composite as a substitute for bone powder, using FT-IR spectroscopy

Chemically synthesized hydroxyapatite/poly- l-lactide (HAp/PLLA) composite biomaterial was studied in vivo. The biocomposite was implanted into Balb/c Singen mice and after 1 and 3 weeks removed from their organisms and analyzed by the FT-IR spectroscopy. After 1 week of testing in vivo the implanted sample gave a spectrum in which absorption bands arising from newly formed functional groups of amine and peptide can be seen. After 3 weeks, a spectrum with pronounced absorption bands at 3420 and 1650 cm −1 assigned to newly generated collagen, a component of the extracellular connective-tissue matrix, was registered. Also, decrease of the intensity absorption band at 1760 cm −1 originating from the CO group of PLLA indicates bioresorption of the PLLA used. Analysis of the microstructure of the sample surface by scanning electron microscopy before and after implantation revealed bioresorption of the PLLA polymer phase and generation of collagen fibers at the sites of implanted bioresorptive PLLA. A mixture of autologous bone powder and HAp/PLLA biocomposite was also examined. After implantation, the same final products as in the case of HAp/PLLA composite biomaterial used alone were found.

Analysis of In Vivo Substitution of Bone Tissue by HAp/PLLA Composite Biomaterial with PLLA of Different Molecular Weights Using FTIR Spectroscopy

Hydroxyapatite/poly-L-lactide (HAp/PLLA) composite biomaterial with PLLA of 50,000 and 430,000 g/mole molecular weight was studied in vivo. The biocomposite with PLLA of both molecular weights was implanted into mice and after 1 and 3 weeks removed from their organisms and analyzed by the FT-IR spectroscopy. After one week of testing in vivo, the implanted samples gave spectra in which absorption bands arising from new-formed functional groups of amine and peptide can be seen. Analysis of the spectra revealed faster formation of peptide compounds when the biocomposite with PLLA of lower molecular weight was used. After 3 weeks, the spectra of the biocomposite of both compositions were registered with pronounced absorption bands at about 3420 and 1650 cm -1 assigned to new-generated collagen, a component of the extracellular connective-tissue matrix. Also, in the case of the biocomposite sample with PLLA of lower molecular weight, disappearance of the previously present absorption band at about 1760 cm -1 originating from the C=O group of PLLA indicates complete bioresorption of the PLLA used. Analysis of the microstructures of the sample surfaces by scanning electron microscopy before and after implantation revealed bioresorption of the PLLA polymer phase in the system with PLLA of lower molecular weight and generation of collagen fibers at the sites of implanted bioresorptive PLLA. A mixture of autologous bone powder and HAp/PLLA biocomposite was also examined. After implantation, the same final products as in the case of HAp/PLLA composite biomaterial alone were found.