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Spherical BSA loaded microporous matrix type microspheres composed of P(HB-HV) blended with 20% PCL II and fabricated using 0/W emulsification with solvent evaporation have been incubated in Hanks' buffer, pH 7.4; newborn calf serum; 1.5% pancreatin and synthetic gastric juice over 30 days and their percentage weight loss (PWL) and changes in ultrastructural morphology monitored by gravimetry and SEM respectively. The greatest percentage weight loss was observed after incubation in newborn calf serum and decreased in the order newborn calf serum > pancreatin > synthetic gastric juice > Hanks' buffer. Only incubation in synthetic gastric juice and Hanks' buffer produced a significant increase in PWL with increasing theoretical percentage loading. Incubation in Hanks' buffer produced limited surface erosion leading to an increase in micropore diameter and the coalescence of micropores to from surface pits. With pancreatin, surface erosion led to the disappearance of surface micropores and a reduction in microsphere diameter. Subsequent fracturing of the microsphere surface facilitated the breakup of the matrix. In synthetic gastric juice there was little surface erosion and surface flaking and bulk erosion were responsible for the breakup of the matrix. In newborn calf serum, spherical shape was maintained despite a reduction in microsphere diameter. Bulk erosion in the form of large macroporous pits extending deep into the matrix gave the microspheres a hollow appearance. The enhanced biodegradation in NCS and significant surface erosion in pancreatin was assumed to be due to the effects of exogenous enzyme activity in addition to simple ester hydrolysis.
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PMID:In vitro biodegradation of poly(beta-hydroxybutyrate-hydroxyvalerate) microspheres exposed to Hanks' buffer, newborn calf serum, pancreatin and synthetic gastric juice. 888 Apr 39

Cyclosporine (CyA) was incorporated into polycaprolactone nanoparticles (PCL-NP) in order to increase its oral bioavailability and to control drug distribution, thereby potentially reducing its toxicity. Prior to in vivo studies, the carrier was optimized and characterized by using different techniques. Light scattering (LS) and transmission and scanning electron microscopy (TEM and SEM) indicated the NP were spherical in shape with a mean size of approximately 100 nm. The influence of the solvent evaporation conditions and the polymer and drug amounts on CyA incorporation was established in order to optimize drug loading. When acetone and excess water were removed at constant temperature, no aggregation phenomena were observed. A value of 180 mg PCL was the minimum polymer amount necessary to encapsulate 95% of the drug initially added to the preparation. Under these conditions, HPLC analysis revealed that approximately 130 microg CyA per mg PCL were incorporated for a total CyA concentration of 2.5 mg/ml, being part of the drug adsorbed onto the particle surface. No structural changes or instability of the components during NP preparation were detected by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). However, GPC studies showed a competition between poloxamer and CyA for adsorption onto the carrier. In addition, DSC results suggested that at least part of the drug associated to NP remained in its crystal form. Therefore, CyA-loaded NP were easily manufactured and characterized and allow for the administration of therapeutic drug doses to experimental animals.
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PMID:Biodegradable nanoparticles as a delivery system for cyclosporine: preparation and characterization. 1103 19

A novel class of multiblock poly(epsilon-caprolactone)-based polymers containing hydrophilic trioxyethylene segments and potentially relevant to the delivery of drugs is described in this work. L-phenylalanine residues may also be inserted into the hydrophilic blocks to generate peptide bonds susceptible to enzymatic attack. The investigated polymers were poly(ether-ester-amide)s (PEEAs) obtained by a two-step polymerization procedure from OH-end capped low molecular weight poly(epsilon-caprolactone), sebacoyl chloride and either 4,7,10-trioxa-1,13-tridecanediamine (PEEA1) or 1,13-di(L-phenylalaninamido)-4,7,10-trioxatridecane (PEEA2). PEEAs were characterized by 1H-NMR spectroscopy, differential scanning calorimetry, gel permeation chromatography and were tested for their suitability in producing microspheres. Particles obtained by the single emulsion-solvent evaporation technique were regular and smooth (SEM analysis) showing a monomodal distribution of dimensions. To assess the potentiality of PEEAs in the oral delivery of drugs, three model compounds with different pKa and solubilities--diclofenac, nicardipine and dicumarol--were encapsulated within PEEA microspheres. For the sake of comparison, microspheres prepared from poly(epsilon-caprolactone) (PCL) with a molecular weight similar to PEEAs were also prepared and tested. The release of diclofenac from all the microspheres was very rapid (100% released within 2 h) whereas nicardipine release was slower and biphasic. The initial phase approximated a near zero-order release, being the fraction of nicardipine released after 8 h from PEEA microspheres higher with respect to PCL particles (about 70 vs. 30%). This result was ascribed to the lower crystallinity of PEEAs with respect to PCL which results in a facilitated access of water molecules through the polymer matrix. The lipophilic-unionizable dicumarol was released from PEEA microspheres at a very slow rate. Therefore, dicumarol-loaded PEEA2 microspheres allowed the study of the influence on the release rate of the insertion into the polymer chain of enzymatically degradable bonds. PEEA2 microspheres released dicumarol at the same rate in a medium with or without the proteolitic enzyme alpha-chymotrypsin. Although the insertion of an isolated amino acid was not sufficient to confer enzyme susceptibility to the polymer, the distinctive properties of PEEAs make their use very attractive in the field of controlled release.
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PMID:Biodegradable microspheres of novel segmented poly(ether-ester-amide)s based on poly(epsilon-caprolactone) for the delivery of bioactive compounds. 1133 10

Biocomposite films comprising a non-crosslinked, natural polymer (collagen) and a synthetic polymer, poly(epsilon-caprolactone) (PCL), have been produced by impregnation of lyophilised collagen mats with a solution of PCL in dichloromethane followed by solvent evaporation. This approach avoids the toxicity problems associated with chemical crosslinking. Distinct changes in film morphology, from continuous surface coating to open porous format, were achieved by variation of processing parameters such as collagen:PCL ratio and the weight of the starting lyophilised collagen mat. Collagenase digestion indicated that the collagen content of 1:4 and 1:8 collagen:PCL biocomposites was almost totally accessible for enzymatic digestion indicating a high degree of collagen exposure for interaction with other ECM proteins or cells contacting the biomaterial surface. Much reduced collagen exposure (around 50%) was measured for the 1:20 collagen:PCL materials. These findings were consistent with the SEM examination of collagen:PCL biocomposites which revealed a highly porous morphology for the 1:4 and 1:8 blends but virtually complete coverage of the collagen component by PCL in the 1:20 samples. Investigations of the attachment and spreading characteristics of human osteoblast (HOB) cells on PCL films and collagen:PCL materials respectively, indicated that HOB cells poorly recognised PCL but attachment and spreading were much improved on the biocomposites. The non-chemically crosslinked, collagen:PCL biocomposites described are expected to provide a useful addition to the range of biomaterials and matrix systems for tissue engineering.
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PMID:Biocomposites of non-crosslinked natural and synthetic polymers. 1196 51

To increase the local concentration of tamoxifen in estrogen receptor (ER) positive breast cancer, we have developed and characterized nanoparticle formulation using poly(epsilon -caprolactone) (PCL). The nanoparticles were prepared by solvent displacement method using acetone-water system. Particle size analysis, scanning electron microscopy, zeta potential measurements, and differential scanning calorimetry (DSC) were used for nanoparticle characterization. Biodegradation studies were performed in the presence and absence of Pseudomonas lipase in phosphate-buffered saline (PBS, pH 7.4) at 37 degrees C. Tamoxifen loading over different concentrations was analyzed by high-performance liquid chromatography (HPLC) and the optimum loading concentration was determined. In vitro release studies were performed in 0.5% (w/v) sodium lauryl sulfate (SLS) containing PBS at 37 degrees C. Cellular uptake and distribution of fluorescent-labeled nanoparticles was examined in MCF-7 breast cancer cells. SEM micrographs and Coulter analysis showed nanoparticles with spherical shape and uniform size distribution (250-300 nm), respectively. Zeta potential analysis revealed a positive surface charge of +25 mV on the tamoxifen-loaded formulation. Being hydrophobic crystalline polyester, PCL did not degrade in PBS alone, but the degradation was enhanced by the presence of lipase. The maximum tamoxifen loading efficiency was 64%. Initial burst release of tamoxifen was observed, probably due to significant surface presence of the drug on the nanoparticles. A large fraction of the administered nanoparticle dose was taken up by MCF-7 cells through non-specific endocytosis. The nanoparticles were found in the perinuclear region after 1 h. Results of the study suggest that nanoparticle formulations of selective ER modulators, like tamoxifen, would provide increased therapeutic benefit by delivering the drug in the vicinity of the ER.
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PMID:Biodegradable poly(epsilon -caprolactone) nanoparticles for tumor-targeted delivery of tamoxifen. 1243 41

The biodegradability of poly(epsilon-caprolactone) (PCL) was studied in blends and composites of modified and granular starch. Four types of PCL-starch compositions were prepared: (i) PCL-granular starch blends; (ii) hydrophobic coating of starch particles by n-butylisocyanate (C(4) starch) and octadecyltrichlorosilane (C(18) starch), followed by melt blending with PCL; (iii) PCL-starch blends compatibilized by PCL-g-dextran grafted copolymer (PGD); and (iv) PCL-grafted starch particles (PGS) as obtained by in situ ring-opening polymerization of caprolactone (CL) initiated directly from hydroxyl functions at the granular starch surface. Biodegradability of these materials was measured by monitoring the percentage of weight loss in composting and the rate of fungal colonization when samples were used as a sole carbon source for fungus (A. niger). Intrinsic viscosity [eta] of host PCL chains was measured after extraction of composted samples in boiled chloroform. SEM was used to study the surface morphology after compost incubation of the samples. The inherent biodegradability of host polymer was enhanced with surface compatibilization during composting for longer incubation. It was observed that the weight loss during composting increased with the decrease in interfacial tension between filler and polymer. In general, it was concluded that inherent biodegradability does not depend very significantly on the concentration of starch in the polyester matrix, but on the compatibilization efficiency. The effect of the PCL fraction in the graft copolymer, when used as compatibilizer, was also studied on the biodegradability of the host polymer.
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PMID:Biodegradation of poly(epsilon-caprolactone)/starch blends and composites in composting and culture environments: the effect of compatibilization on the inherent biodegradability of the host polymer. 1289 43

Present study describes the development of a new formulation of levonorgestrel and ethinylestradiol based on double emulsion-solvent evaporation technique using poly(epsilon-caprolactone) (PCL) as biodegradable polymer. The effect of polymer concentration on microspheres and entrapment of drug into microspheres were studied. PCL was selected because of its hydrophobicity and advantages over other biodegradable polymers. Characterization of biodegradable polymer used for controlled drug delivery is essential to ensure reproducibility of in vitro and in vivo performances. The selected characterisation techniques established for PCL microspheres include its loading and entrapment efficiencies, DSC to analyse thermal behaviour, SEM to observe surface morphology, drug content of microspheres and in vitro release of drugs from microspheres. The SEM reports showed that microspheres were with smooth surface and DSC thermograms revealed no interaction between drug and polymer. The entrapment was found to be 58 and 47% for 1:10 and 1:5 batches and in vitro release studies showed that about 69.7% of LNG and 66.7% of EE from 1:10 batch and about 80% of LNG and 75.5% of EE from 1:5 batch for 150 days.
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PMID:Preparation and characterization of injectable microspheres of contraceptive hormones. 1464 73

New acrylic-based cements were formulated by replacing a mass fraction of 20% of poly(methyl methacrylate) (PMMA) powder by PMMA/poly(epsilon-caprolactone) (PCL) beads (throughout this article all compositions are given as mass fractions, unless specified otherwise). PMMA/PCL beads containing 10 and 30% PCL were synthesized by suspension polymerization. Cements were prepared by replacing part of the PMMA powder of the formulation by an equivalent mass of PMMA/PCL particles. The influence of the PCL content in the beads on the mechanical behavior was assessed by testing the cements in flexure and compression. The addition of PMMA/PCL particles with 10% PCL content resulted in a marked increase in both flexural modulus and flexural strength related to the plain PMMA beads formulation. This improvement was attributed to a decrease in the cured material porosity. Conversely, by the incorporation of beads with 30% PCL content the flexural properties decreased. This behavior was attributed to the debonding of the particles from the matrix, which was revealed by SEM images. The observed compressive yield strength decrease with the increase of PCL content in the beads was attributed to a low degree of adhesion between the heterogeneous particles and the matrix as well as to the plasticizing effect of the PCL.
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PMID:Mechanical characterization of self-curing acrylic cements formulated with poly(methylmethacrylate)/poly(epsilon-caprolactone) beads. 1526 17

Tissue engineering offers the potential of providing vessels that can be used to replace diseased and damaged native blood vessels. The endothelization of a synthetic vascular graft minimizes the failures associated with blood clotting and platelet activation. The aim of this study was to culture vascular-derived endothelial and smooth muscle cells on both untreated and NaOH-treated poly(epsilon-caprolactone) (PCL) films, a biocompatible and bio-resorbable polymer, and to evaluate the behavior of both cell types as a preliminary study for vascular graft development. PCL films were prepared by hot pressing; characterized by DSC, IR, SEM, and scanning force microscopy; and treated with NaOH to increase the surface hydrophilicity before cell culture. Endothelial and smooth muscle cells, isolated from pig cava vein, were characterized by immunofluorescence and confocal microscopy studies of endothelial nitric oxide synthase and alpha-smooth muscle actin. Good adhesion, growth, viability and morphology of both the endothelial and smooth muscle cells on PCL films were obtained, but a light stimulation of mitochondrial activity was observed during short culture times. NaOH treatment improved the adhesion and enhanced the proliferation in both cell types. This verified the possible use of this modified polymer as a support in the preparation of a synthetic vascular graft. [Diagram: see text] SEM micrograph of smooth muscle cells cultured on NaOH-treated PCL film. (Original magnification: 1000x).
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PMID:Vascular endothelial and smooth muscle cell culture on NaOH-treated poly(epsilon-caprolactone) films: a preliminary study for vascular graft development. 1589 76

The biodegradable poly(epsilon-caprolactone) microcapsules (PCL) containing tocopherol (TC) were prepared by emulsion solvent evaporation method, and microcapsules were treated by oxygen plasma to enhance the hydrophilic microcapsules. The morphologies and thermal properties of the microcapsules were determined by SEM and DSC measurements. The microcapsules studied were characterized by surface free energy or work of adhesion through contact angle measurement. As a result, the features of the microcapsules could be adjusted by manufacturing condition, such as surfactant and core ratio. The surface free energy or work of adhesion of the microcapsules was increased with increasing the time of plasma treatment, which could be attributed to the increased hydrophilic groups during oxygen plasma treatment. The release profile of the microcapsules was determined by UV-vis spectroscopy and the microcapsules containing tocopherol showed the rapid release rate, as compared with untreated ones.
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PMID:Effect of oxygen plasma treatment on the release behaviors of poly(epsilon-caprolactone) microcapsules containing tocopherol. 1593 81


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