|Articles about Biomaterials|
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| Bone-like polyethelyne burr-hole cover
Dujovny, M., A. Aviles, et al. (2005), Neurol Res 27(3): 333-4.
Abstract: OBJECTIVE: Several materials are available for covering burr holes but none of them are ideal with respect to biocompatibility, strength and morbidity. With these properties in mind, our objective was to design a porous polyethylene device, which looked like bone and provides protection and cosmesis while being quick and easy to apply. METHODS AND MATERIALS/RESULTS: A burr-hole cover was created to cover small cranial defects and craniostomies. Using high-density polyethylene, this cover was designed to resemble the bony structure of the skull. Its porous architecture allows for tissue ingrowth and bony integration. It consists of a cylinder which fits into the burr hole and a cap which can be sutured or anchored with titanium screws. CONCLUSIONS: The "bone-like" burr-hole cover provides adequate protection, biocompatibility and cosmesis and is simple to use. Alternative implants can be toxic to surrounding tissues, costly and time consuming to apply. This high-density polyethylene cover is compatible with surrounding tissue as well as being of a porous nature and the material it is made from offers high tensile strength for adequate protection.
| BoneSource hydroxyapatite cement: a novel biomaterial for craniofacial skeletal tissue engineering and reconstruction
Friedman, C. D., P. D. Costantino, et al. (1998), J Biomed Mater Res 43(4): 428-32.
Abstract: BoneSource-hydroxyapatite cement is a new self-setting calcium phosphate cement biomaterial. Its unique and innovative physical chemistry coupled with enhanced biocompatibility make it useful for craniofacial skeletal reconstruction. The general properties and clinical use guidelines are reviewed. The biomaterial and surgical applications offer insight into improved outcomes and potential new uses for hydroxyapatite cement systems.
| Bone--special problems of the craniofacial region
Herring, S. W. and P. Ochareon (2005), Orthod Craniofac Res 8(3): 174-82.
Abstract: PROBLEMS: The craniofacial region presents special problems for tissue engineering. First, the stresses and strains that engineered tissues will encounter are mostly unknown. Second, if tissue engineering is to be useful in ameliorating craniofacial anomalies, it will have to mimic the growth activity of the native tissues. These problems are interrelated in that bone growth responds to loading conditions. METHODS: Our work uses miniature technology to measure skull deformation during function in the miniature pig. Growth is quantified in the same animals by labeling replicating cells with bromodeoxyuridine and newly mineralized bone with fluorochromes. The mandibular condyle and the cranial sutures are both candidate areas for tissue engineering, and craniofacial periosteum is a promising graft material. RESULTS: The condyle is compressed by the reaction load at the temporomandibular joint (TMJ). Cell divisions in the perichondrium are negatively correlated with bone strain. Craniofacial sutures deform during function much more than adjacent bones, and strains can be either tensile or compressive. In contrast to expectation, functional tension is not correlated with sutural growth rate. However, functional strain does predict sutural morphology, with compressed sutures showing complex interdigitation. Periosteum shows striking differences between resorptive and appositional surfaces. The resorptive medial side of the zygomatic arch is under pressure during function. Tensile strain perpendicular to the surface is probably greater on the temporal than on the zygomatic bone, thus correlating with more rapid periosteal apposition on the temporal. CONCLUSION: Engineered implants may be more likely to succeed if their architecture suits the strain environment in which they will function.
| Bovine BMP osteoinductive potential enhanced by functionalized dextran-derived hydrogels
Maire, M., F. Chaubet, et al. (2005), Biomaterials 26(24): 5085-92.
Abstract: This study evaluated functionalized dextran-derived hydrogels as BMP carriers using both in vitro and in vivo models. In vitro release kinetics indicated that dextran-derived hydrogels could retain rhBMP-2 growth factor in a variable manner depending on their functionalization ratio. The potential of these hydrogels when combined with extracted bovine BMP to enhance the bone formation was evaluated in a rat ectopic model. The largest osteoinduction was found when using hydrogels exhibiting the highest growth factor retention capacity. In addition, some implanted hydrogels demonstrated a capacity to induce an in-vivo calcification certainly related to their chemical composition. These properties make these materials interesting osteoconductive BMP carriers, allowing to decrease the amount of implanted factor required for bone regeneration.
| Breast implant fears put focus on biomaterials
Weiss, R. (1991), Science 252(5010): 1059-60.
| Buccal penetration enhancement properties of N-trimethyl chitosan: Influence of quaternization degree on absorption of a high molecular weight molecule
Sandri, G., S. Rossi, et al. (2005), Int J Pharm 297(1-2): 146-55.
Abstract: The aim was to evaluate the influence of the degree of quaternization of N-trimethyl chitosans (TMCs) on the mucoadhesive and penetration enhancement properties towards buccal mucosa. Fluorescein isothiocyanate dextran (MW 4400 Da) (FD4) was used as model molecule. TMCs, obtained from chitosans of different MW (1460 and 580 kDa, respectively), were hydrated in distilled water and in pH 6.4 phosphate buffer (simulating the buccal fluid). The polymer solutions were subjected to mucoadhesion measurements towards bovine submaxillary mucin dispersion and porcine buccal mucosa and to FD4 permeation tests through porcine cheek epithelium. The trimethylation of chitosan allows maintenance or improvement of the mucoadhesive properties of the starting chitosans dependently on quaternization degree. In particular, the mucoadhesive properties increase on increasing degree of quaternization. The trimethylation does not produce any change in chitosan penetration enhancement properties when the medium is distilled water while if pH 6.4 buffer is used, the trimethylation produces an improvement in chitosan penetration enhancing effect. TMC derived from the lower MW chitosan and characterized by the highest degree of quaternization shows the best mucoadhesive and penetration enhancement properties and is the most promising TMC to improve the bioavailability of hydrophilic and large MW molecules (like peptides and proteins) when administered via buccal route.
| Building structured biomaterials using AC electrokinetics
Alp, B., J. S. Andrews, et al. (2003), IEEE Eng Med Biol Mag 22(6): 91-7.
| Business models for biomaterials in regenerative medicine
Williams, D. (2005), Med Device Technol 16(5): 7-8.
Abstract: The emergence of new therapeutic methods and technologies, including those associated with regenerative medicine, has required new thinking about regulation, reimbursement and business models. Some of the issues that particularly relate to the materials used in these technologies are discussed in this article.
| Ca/P mol ratio of cries-affected dentin structures
Hashemi, Z. K., Y. Oshida, et al. (2005), Biomed Mater Eng 15(4): 251-60.
Abstract: BACKGROUND: A new approach called "minimum intervention" has been introduced for restoration of carious lesions to preserve tooth structure. This approach suggests that perhaps caries need not always be removed completely from deeper portions of the cavity. It is, therefore, important to characterize caries-affected dentin structures, because of the potential changes in bonding quality when using different dentinal substrates. MATERIALS AND METHOD: Ninety teeth (30 teeth each group) were studied. The first group (CF) consisted of 30 caries-free teeth. The second group (CC) consisted of 30 teeth, for which caries-free dentin teeth was chemically demineralized. The third group (ND) consisted of 30 extracted human molars with coronal carious lesions. After all tooth samples were water-polished with grit #600 SiC paper, they were tested by surface contact angle measurements and the electron-probe microanalyzer to measure Ca/P mol ratio. RESULTS: Contact angles were CF = 60.07 degrees; CC = 30.8 degrees; ND = 26.11 degrees, p<0.05. Ca/P mol ratios were as follows; CF = 1.549 (+/-0.0435); CC = 1.324 (+/-0.2305); ND = 1.568 (+/-0.0523), p<0.05. Weibull analyses for Ca/P mol ratio indicated shape parameter (m) of CF was 13.3; it was 12.8 for ND and 11.8 for CC. Above the delta point (=1.65 in Ca/P ratio), for both groups m = 3.4. CONCLUSION: Caries-affected dentin surfaces (naturally-developed and chemically created) were statistically more chemically active than caries-free dentin surface. Ca/P mol ratio of chemically created caries was less than other two groups.
| Calcification as an indicator of osteoinductive capacity of biomaterials in osteoblastic cell cultures
Declercq, H. A., R. M. Verbeeck, et al. (2005), Biomaterials 26(24): 4964-74.
Abstract: Mineralized extracellular matrix formation is representative for the osteoinductive capacity of biomaterials and is often tested in vitro. Characteristics of in vitro mineralization of primary rat osteoblastic cells (bone marrow, calvaria, periosteum, fetal and adult long bone) and UMR-106 cells were compared by von Kossa staining, FTIR, X-ray diffractometry, TEM and related to parameters of early (ALP and collagen I formation) and late (osteocalcin secretion) osteoblast expression. All cultures expressed high alkaline phosphatase activity and were able to form bone apatite. However, a nodular versus diffuse mineralization pattern was observed. Bone marrow, calvaria and periosteum (early passage) derived cells mineralized restrictively on the three-dimensional area of a nodule. The extracellular matrix consisted of collagen I fibers, among matrix vesicles loaded with needle-like crystals. Long bone, late passage periosteum derived and UMR-106 cells exhibited a diffuse mineralization pattern. Needle-like crystals were observed between the cells but collagen fibers and matrix vesicles could not be detected. Secretion of osteocalcin was detected in cultures derived from bone marrow and absent in UMR-106 and long bone derived cell cultures. The present study demonstrates that dystrophic calcification can not be distinguished from cell-mediated calcification with von Kossa, FTIR and X-ray diffractometry. Primary osteoblastic cells capable of forming nodules are recommended to evaluate the osteoinductive properties of biomaterials.
| Calcification of advanced atherosclerotic lesions in the innominate arteries of ApoE-deficient mice: potential role of chondrocyte-like cells
Rattazzi, M., B. J. Bennett, et al. (2005), Arterioscler Thromb Vasc Biol 25(7): 1420-5.
Abstract: OBJECTIVE: Advanced atherosclerotic lesions in the innominate arteries of chow-fed apolipoprotein E-deficient mice become highly calcified with 100% frequency by 75 weeks of age. The time course, cell types, and mechanism(s) associated with calcification were investigated. METHODS AND RESULTS: The deposition of hydroxyapatite is preceded by the formation of fibro-fatty nodules that are populated by cells that morphologically resemble chondrocytes. These cells are spatially associated with small deposits of hydroxyapatite in animals between 45 and 60 weeks of age. Immunocytochemical analyses with antibodies recognizing known chondrocyte proteins show that these cells express the same proteins as chondrocytes within developing bone. Histological and electron microscopic analyses of lesions from animals between 45 and 60 weeks of age show that the chondrocyte-like cells are surrounded by dense connective tissue that stains positive for type II collagen. Nanocrystals of hydroxyapatite can be seen within matrix vesicles derived from the chondrocyte-like cells. In mice between 75 and 104 weeks of age, the lesions have significantly reduced cellularity and contain large calcium deposits. The few remaining chondrocyte-like cells are located adjacent to or within the large areas of calcification. CONCLUSIONS: Calcification of advanced lesions in chow-fed apolipoprotein E-deficient mice occurs reproducibly in mice between 45 and 75 weeks of age. The deposition of hydroxyapatite is mediated by chondrocytes, which suggests that the mechanism of calcification may in part recapitulate the process of endochondral bone formation.
| Calcification of senile cataractous lens determined by Fourier transform infrared (FTIR) and Raman microspectroscopies
Chen, K. H., W. T. Cheng, et al. (2005), J Microsc 219(Pt 1): 36-41.
Abstract: A calcified plaque on the surface of a senile cataractous lens (CL) isolated from a 79-year-old male patient was identified and its chemical composition quantified using Fourier transform infrared (FTIR) and confocal Raman microspectroscopies. The noncalcified area of the same CL and hydroxyapatite (HA) were selected as a control. Several unique absorption bands, at 960, 1034 and 1090 cm(-1) assigned to the nu(1) and nu(3) stretching modes of phosphate and at 875 cm(-1) attributed to carbonate, were clearly displayed in the infrared (IR) spectra of calcified plaque and HA. A peak at 961 cm(-1) due to the nu(1) stretching mode of phosphate was also evidenced in the Raman spectra of calcified plaque and HA. The calcified plaque formed within the lens protein was found to mainly consist of a mature HA, in which type-A carbonate apatites (11.4%), type-B carbonate apatites (55.6%) and liable surface carbonate ions (33.0%) were presented. A higher content of the liable carbonate implies that the calcification or mineralization in this calcified lens was incomplete and still in progress. Moreover, calcification seems not to influence the secondary structure of lens protein because both IR and Raman spectra for the lens protein in the noncalcified area and calcified plaque were similar. The result suggests that both microscopic FTIR and Raman spectroscopies were easy to perform and capable of determination of the chemical composition of a calcified CL.
| Calcified matrix production by SAOS-2 cells inside a polyurethane porous scaffold, using a perfusion bioreactor
Fassina, L., L. Visai, et al. (2005), Tissue Eng 11(5-6): 685-700.
Abstract: The repair and regeneration of damaged or resected bone are problematic. Bone autografts show optimal skeletal incorporation, but often bring about complications. Hence, there is increasing interest in designing new biomaterials that could potentially be used in the form of scaffolds as bone substitutes. In this study we used a hydrophobic cross-linked polyurethane in a typical tissue-engineering approach, that is, the seeding and in vitro culturing of cells within a porous scaffold. The polyurethane porous scaffold had an average pore diameter of 624 microm. Using a perfusion bioreactor, we investigated the effect of shear stress on SAOS-2 human osteoblast proliferation and calcified matrix production. The physical, morphological, and compressive properties of the polyurethane foam were characterized. At a scaffold perfusion rate of 3 mL/min, in comparison with static conditions without perfusion, we observed 33% higher cell proliferation; higher secretion of osteopontin, osteocalcin, decorin, and type I collagen (9.16-fold, 71.9-fold, 30.6-fold, and 18.12-fold, respectively); and 10-fold increased calcium deposition. The design of the bioreactor and the design of the polyurethane foam aimed at obtaining cell colonization and calcified matrix deposition. This cultured biomaterial could be used, in clinical applications, as an osteoinductive implant for bone repair.
| Calcitonin stimulates multiple stages of angiogenesis by directly acting on endothelial cells
Chigurupati, S., T. Kulkarni, et al. (2005), Cancer Res 65(18): 8519-29.
Abstract: Although a strong correlation between neuroendocrine differentiation and angiogenesis of prostate cancer has been reported, no mechanistic link between the two events has been established. Because neuropeptide calcitonin is secreted by prostate tumors and endothelial cells are known to express calcitonin receptor-like receptor, we examined the potential action of calcitonin on endothelial cells. The presence of calcitonin receptor, calcitonin receptor-like receptor, and receptor activity-modifying proteins in human microvessel endothelial-1 cells was tested by reverse transcriptase-PCR (RT-PCR). The proangiogenic action of calcitonin was examined in several in vitro models of angiogenesis using HMEC-1 cells and also in vivo using dorsal skinfold assays. Calcitonin expression of PC-3M cells was modulated, and its effect on angiogenesis was examined in in vitro as well as in vivo models. The results of RT-PCR and radioligand receptor assays showed the presence of functional calcitonin receptor in HMEC-1 cells. Calcitonin stimulated all phases of angiogenesis through the calcitonin receptor, but its effect on tube morphogenesis by endothelial cells occurred at the concentration of the Kd of calcitonin receptor. Silencing of calcitonin receptor expression in HMEC-1 cells abolished calcitonin-induced tube formation. Vascular endothelial growth factor antibodies attenuated but did not abolish calcitonin-induced tube morphogenesis. PC-3M prostate cancer cells induced angiogenesis in in vivo and in vitro models. Overexpression of calcitonin in PC-3M cells increased their angiogenic activity, whereas the silencing of calcitonin expression abolished it. These results show that prostate tumor-derived calcitonin may play an important role in prostate tumor growth by regulating intratumoral vascularization.
| Calcium phosphate biomaterials and bone mineral. Differences in composition, structures and properties
Rey, C. (1990), Biomaterials 11: 13-5.
Abstract: Most calcium phosphates used as biomaterials are well characterized high temperature compounds presenting both bulk and surface properties very different from those of bone mineral. The composition and structure of biomaterials and bone mineral are discussed in order to highlight the differences and determine their consequences on biological behaviour.
| Calcium phosphate cement composites in revision hip arthroplasty
Speirs, A. D., T. R. Oxland, et al. (2005), Biomaterials 26(35): 7310-8.
Abstract: Loosening of the femoral component in a total hip arthroplasty with concomitant bone loss can pose a problem for revision surgery due to inadequate structure in the remaining femur. While impaction allografting has shown promise, it has also shown serious complications, especially with moderate to severe bone loss. It may be possible to stabilize the graft layer with a bioresorbable cement to improve clinical results. This study examines the mechanical properties of a potential morsellized bone-bioresorbable composite. Morsellized bone was mixed with a commercially available bioresorbable cement (alpha-BSM, Etex Corp.) in compositions of 0%, 25%, 50% and 75% bone. Unconfined compression and diametral tensile and confined compression tests were performed to determine the composite mechanical properties. The composition containing 50% bone tended to exhibit the highest uniaxial strengths, as well as the highest confined compression modulus. The uniaxial compressive strength and stiffness of this composition was in the range of cancellous bone. Uniaxial compressive modulus decreased with increasing bone fraction whereas elongation exhibited the opposite trend. Bone fraction had a significant effect on compressive strength (p < 0.0001), compressive modulus (p < 0.0001), elongation (p < 0.01), tensile strength (p < 0.0001) and confined compressive modulus (p = 0.04). The addition of a bioresorbable cement to the allograft layer may improve the properties of the layer, preventing early subsidence seen in some clinical studies of impaction allografting, and therefore improving the clinical results. Further testing is required to evaluate the in vitro mechanical performance, as well as in vivo remodelling characteristics.
| Calcium-induced virulence factors associated with the extracellular matrix of mucoid Pseudomonas aeruginosa biofilms
Sarkisova, S., M. A. Patrauchan, et al. (2005), J Bacteriol 187(13): 4327-37.
Abstract: Pseudomonas aeruginosa colonizes the pulmonary tissue of patients with cystic fibrosis (CF), leading to biofilm-associated infections. The pulmonary fluid of CF patients usually contains elevated concentrations of cations and may contain the P. aeruginosa redox-active pigment pyocyanin, which is known to disrupt calcium homeostasis of host cells. Since divalent cations are important bridging ions for bacterial polysaccharides and since they may play regulatory roles in bacterial gene expression, we investigated the effect of calcium ions on the extracellular matrix constituents of P. aeruginosa biofilms. For mucoid strain P. aeruginosa FRD1, calcium addition (1.0 and 10 mM as CaCl(2)) resulted in biofilms that were at least 10-fold thicker than biofilms without added calcium. Scanning confocal laser microscopy showed increased spacing between cells for the thick biofilms, and Fourier transform infrared spectroscopy revealed that the material between cells is primarily alginate. An algD transcriptional reporter demonstrated that calcium addition caused an eightfold increase in alg gene expression in FRD1 biofilms. Calcium addition also resulted in increased amounts of three extracellular proteases (AprA, LasB, and PrpL). Immunoblots of the biofilm extracellular material established that AprA was harbored within the biofilm extracellular matrix. An aprA deletion mutation and a mutation in gene for a putative P. aeruginosa calmodulin-like protein did not significantly affect calcium-induced biofilm structure. Two-dimensional gel electrophoresis showed increased amounts of phenazine biosynthetic proteins in FRD1 biofilms and in calcium-amended planktonic cultures. Spectrochemical analyses showed that the calcium addition causes a three- to fivefold increase in pyocyanin production. These results demonstrate that calcium addition affects the structure and extracellular matrix composition of mucoid P. aeruginosa biofilms, through increased expression and stability of bacterial extracellular products. The calcium-induced extracellular matrix of mucoid P. aeruginosa consists primarily of the virulence factor alginate and also harbors extracellular proteases and perhaps pyocyanin, a biomolecule that may further disrupt cellular calcium levels.
| Can magnetic resonance imaging be the key technique to visualize and investigate endovascular biomaterials?
Guidoin, R., F. Langevin, et al. (2004), Artif Cells Blood Substit Immobil Biotechnol 32(1): 105-27.
Abstract: OBJECTIVE: Magnetic resonance imaging (MRI) is an established modality in clinical use but may be potentially underutilized to visualize and investigate biomaterials. As its use is totally contraindicated only for ferromagnetic devices, it was employed to visualize deployment, biofonctionality, healing, and biodurability of a commercially available endovascular device, namely the Medtronic-AVE AneuRx. The quality of the observations coupled with the absence of ionizing radiations are likely to make this technique an attractive imaging modality in the future. METHOD: The potential benefits of the MRI technique were investigated in a GE Vectra-MR 0.5T MRI for the Medtronic-AVE AneuRx endovascular prosthesis, under different conditions: undeployed i.e., inserted in the delivery cartridge as received from the manufacturer (step 1), deployed in a mock glass-aneurysm tube (step 2), and as a pathological explant harvested at the autopsy of a patient (step 3). The device was submitted to X-rays for examination in addition to MRI. At step 3, the device was further investigated with light microscopy and scanning electron microscopy (SEM) together with X-ray diffraction. RESULTS: The device which was inserted and pleated in the delivery cartridge did not demonstrate any significant observation either in MRI or in X-rays. When it was deployed in the mock aneurysmal glass tube, light artefacts were associated with the T2 weighed FSE images around the Nitinol whereas X-rays gave images of indisputable interest. Similar results were noted using the explanted device. Very high contrasts were obtained with T1 whereas T2 images were almost defect free. The X-rays allowed to accurate imaging of the Nitinol skeleton but were poor to discriminate between the different tissues. Pathology observations using light microscopy were not really challenged, as the magnetic resonance imaging was performed using a 0.5T machine. DISCUSSION: The benefits of magnetic resonance imaging as a quality control technique to examine an endovascular device within its cartridge remains ill defined. Similarly, the role of conventional X-rays is unknown. The observation of devices fully deployed in a mock aneurysmal glass-tube under MRI are potentially useful but X-rays images allowed better definition. The MRI examination of the explanted device does permit observations related to the healing of the device that might be obtained in vivo and, thus offers new avenues for the follow-up of implanted devices. The pathological investigations brought additional informations about the tissues and the corrosion of the Nitinol. However, it is unlikely that MRI will permit detailed analysis of the biomaterials and in particular the corrosion process of the stents. CONCLUSION: These early observations of the follow-up of devices using MRI warrant further investigation. The absence of ionizing radiation with MRI makes this technique particularly attractive. As there is no emission of ionizing radiation associated with magnetic resonance, it is recommended that further investigation using this environment friendly technique for the follow-up of devices made of biomaterials that are MRI compatible.
| Capillary electrophoresis of poly(amidoamine) dendrimers: from simple derivatives to complex multifunctional medical nanodevices
Shi, X., I. J. Majoros, et al. (2005), Mol Pharm 2(4): 278-94.
Abstract: Multifunctional poly(amidoamine) (PAMAM) dendrimer-based nanodevices provide novel nanoplatforms for targeting, imaging, and treatment of cancers in vitro and in vivo. Generational, skeletal, and substitutional dispersities are always present in dendrimer-based medical nanodevices. Molecular distribution plays a central role for one to evaluate the quality of PAMAM materials for medical applications. Capillary electrophoresis (CE) has been extensively used as a characterization technique to analyze a range of PAMAM dendrimers, from simple PAMAM derivatives to complex multifunctional PAMAM nanodevices. This review reports the recent advances in the analysis and characterization of a variety of PAMAM dendrimer-based nanoparticles ranging from polycationic and polyanionic PAMAM derivatives to PAMAMs of different generations and defined substitutions, and to complex multifunctional PAMAM nanodevices containing targeting ligands, dyes, and drugs. Understanding the structural complexity of dendrimer nanodevices is crucial for their use as multifunctional imaging, targeting, and cancer therapeutic devices, as well as for their use in biosensing, diagnostics, and control of biological systems.
| Capillary liquid chromatography of chlorophenoxy acid herbicides and their esters in apple juice samples after preconcentration on a cation exchanger based on polydivinylbenzene-N-vinylpyrrolidone
Rosales-Conrado, N., M. E. Leon-Gonzalez, et al. (2005), J Chromatogr A 1076(1-2): 202-6.
Abstract: A capillary liquid chromatography (cLC) method with gradient elution has been used to determine chlorophenoxy acid herbicides: 2,4-dichlorophenoxyacetic acid, 4-chloro-2-methylphenoxyacetic acid, 2-(2,4-dichlorophenoxy)propanoic acid, 2-(4-chloro-2-methylphenoxy)propanoic acid, 4-(2,4-dichlorophenoxy)butanoic acid, 4-(4-chloro-2-methylphenoxy)butanoic acid, 2-(2,4,5-trichlorophenoxy)propanoic acid, 2,4-dichlorophenoxyacetic-1-methyl ester and 2,4-dichlorophenoxyacetic-1-butyl ester in spiked apple juice samples with amounts between 0.025 and 0.150 mg kg(-1) of each herbicide. Clean-up and preconcentration of acid and esters were carried out in an Oasis MCX polymer. Detection limits obtained by cLC, between 0.005 and 0.018 mg kg(-1), allowed the determination of chlorophenoxy acids and their esters in apple juice samples around the levels permitted by the European Regulations, with recoveries in the range 84-99% and RSDs between 1 and 4%.
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