PCL Films Research Articles

Pancreatin enhanced erosion of and macromolecule release from 2,2-bis(2-oxazoline)-linked poly(ϵ-caprolactone)

The degradation and erosion of solvent cast films and injection molded bars prepared from poly(ϵ-caprolactone) (PCL) and 2,2′-bis(2-oxazoline) linked poly(ϵ-caprolactone) (PCL-O) were evaluated in simulated gastric fluid (SGF) (pH 1.2, pepsin present) and in simulated intestinal fluid (SIF) (pH 7.5, pancreatin present). After incubation of the polymer films (10 mg) and bars (70 mg) in the medium, the resulting decrease in molecular weight (degradation) was determined by size exclusion chromatography and the weight loss of the preparations was measured. In addition, the effect of pancreatin on FITC–dextran (MW 4400) release from PCL and PCL-O microparticles, prepared by w/o/w double emulsion technique, was studied. No degradation or weight loss was observed for either PCL or PCL-O films in SGF (12 h incubation, 37 °C). When compared to PBS pH 7.4, pancreatin hardly enhanced the weight loss of PCL films and bars. In contrast, pancreatin enhanced substantially erosion of PCL-O films and bars. Unlike PCL preparations, the PCL-O preparations showed surface erosion in SIF. Pancreatin increased considerably FITC–dextran release from both PCL and PCL-O microparticles. In conclusion, the present results demonstrate the enzyme sensitivity of the novel PCL-O polymer. In addition, the results show that pancreatin present in intestinal fluid may substantially affect drug release from PCL based preparations.

Blends of aliphatic polyesters. VIII. Effects of poly(L‐lactide‐co‐ε‐caprolactone) on enzymatic hydrolysis of poly(L‐lactide), poly(ε‐caprolactone), and their blend films

AbstractPoly(L‐lactide), that is, poly(L‐lactic acid) (PLLA), poly(ε‐caprolactone) (PCL), and their blend (50/50) films containing different amounts of poly(L‐lactide‐co‐ε‐caprolactone) (PLLA‐CL), were prepared by solution casting. The effects of added PLLA‐CL on the enzymatic hydrolysis of the films were investigated in the presence of proteinase K and Rhizopus arrhizus lipase by use of gravimetry. The addition of PLLA‐CL decreased the proteinase K–catalyzed hydrolyzabilities of the PLLA and PLLA/PCL (50/50) films as well as the Rhizopus arrhizus lipase‐catalyzed hydrolyzability of the PCL and PLLA/PCL (50/50) films. The decreased enzymatic hydrolyzabilities of the PLLA and PCL films upon addition of PLLA‐CL are attributable to the fact that the PLLA‐CL is miscible with PLLA and PCL and the dissolved PLLA‐CL must disturb the adsorption and/or scission processes of the enzymes. In addition to this effect, the decreased enzymatic hydrolyzabilities of the PLLA/PCL (50/50) films upon addition of PLLA‐CL can be explained by the enhanced compatibility between the PLLA‐rich and PCL‐rich phases arising from the dissolved PLLA‐CL. These effects result in decreased hydrolyzable interfacial area for PLLA/PCL films. The decrement in proteinase K–catalyzed hydrolyzability of the PLLA film upon addition of PLLA‐CL, which is miscible with PLLA, was in marked contrast with the enhanced proteinase K–catalyzed hydrolyzability of the PLLA film upon addition of PCL, which is immiscible with PLLA. This confirms that the miscibility of the second polymer is crucial to determine the proteinase K–catalyzed hydrolyzabilities of the PLLA‐based blend films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 412–419, 2003

Drug release profiles from and degradation of a novel biodegradable polymer, 2,2-bis(2-oxazoline) linked poly(ε-caprolactone)

In the present study, poly(ε-caprolactone) (PCL) was modified by introducing oxamide groups into PCL (PCL-O). The degradation (decrease in molecular weight) and erosion (weight loss) of PCL and PCL-O films were studied in PBS (pH 7.4, USP XXIV, 37 °C, 26 weeks incubation). The release rates of guaifenesin ( M w 198.2), griseofulvin ( M w 352.8), timolol ( M w 332.4), sodium salicylate ( M w 160.1) and FITC-dextran ( M w 4400) from PCL and PCL-O preparations (solvent cast films, compression-molded plates, midi injection-molded rods and microparticles) were examined in PBS (pH 7.4, 37 °C). The degradation rate of PCL-O film was faster than that of PCL film while no erosion was observed for either film. When compared to the corresponding drug release from PCL films, the release rates of low molecular weight drugs ( M w≤352.8) from PCL-O films were comparable, their releases from both films following closely square-root-of-time kinetics. These results indicate that the oxamide groups had no substantial effect on the release of the low molecular weight drugs. The exception was sodium salicylate which was released faster from PCL-O film. However, FITC-dextran release was notably faster from PCL-O microparticles than from those made of PCL. FITC-dextran release was a combination of diffusion and polymer degradation and thus, the faster degradation of PCL-O enhanced the release of FITC-dextran. In conclusion, the effects of the oxamide groups on drug release profiles were dependent on the drug release mechanisms.

Permeation of protein from porous poly(epsilon-caprolactone) films.

The objective of this study was designed to extend the application of poly(epsilon-caprolactone) (PCL) in delivery of macromolecular proteins. The strategy applied here is to create a porous structure in PCL films in order to control the diffusion rate of protein. Various amounts of both high-molecular-weight and low-molecular-weight poly(ethylene glycol) (PEG) were used as pore-forming agents. The porous films were prepared by a solvent-casting-leaching method. The thicknesses of the prepared films were controlled to be in the range of 75.3 +/- 0.6 similar 81.7 +/- 0.6 mum. The pore fraction of films was determined to be 27.7 +/- 1.0% similar 52.5 +/- 0.8% for PEG(10000) and 26.6 +/- 1.8% similar 48.8 +/- 1.4% for PEG(4000). The pore fraction initially increased with increasing amounts of PEG, independent of the molecular weight of PEG. In the permeation study, lysozyme was used as a model diffuser. The permeation rate of protein increased as the pore fraction of films increased, especially when 30 similar 40% of PEG was added initially, and this phenomenon was more prominent when low-molecular-weight PEG was used. This result was probably due to the highly porous structure creating interconnected channels in the films, further enhancing protein diffusion. In addition, the size of micropores formed by PEG(4000) was observed to be larger than by PEG(10000), which also accounted for faster permeation rate of lysozyme through PCL-PEG(4000) porous films.

Covalent and non-covalently coupled polyester–inorganic composite materials

Two types of organic/inorganic materials were synthesized via sol–gel reactions for tetraethylorthosilicate (TEOS) and organo-alkoxsilane monomers in the presence of poly(ε-caprolactone) (PCL): (1) non-covalent hybrids, in which PCL and silicate, and PCL and organically modified silicate (ORMOSIL), phases are coupled by non-bonded interactions; (2) covalent hybrids in which triethoxysilane–telechelic PCL molecules form chemical bonds with a sol–gel-derived silicate phase. Chemical structures were verified using FTIR and 13C NMR spectroscopies and MALDI-TOF mass spectrometry. The constant PCL phase T g for the silicate–PCL hybrids of (1) implies poor organic/inorganic mixing, but dual-melting endotherms varied with silicate content. TGA revealed significant elevation of degradation onset temperature ( T d) of (1) and suppression of the low temperature chain scission process. No PCL glass transition is seen for ORMOSIL–PCL hybrids where diethoxydimethylsilane is the co-monomer and melting occurs in one step, and there are significant increases in T d. Likewise, no glass transition is seen when acetoxypropyltrimethoxylsilane is the semi-organic co-monomer, but there are dual-melting endotherms. Triethoxysilane-endcapped PCL was synthesized and its microstructure verified by GPC, MALDI-TOF mass spectrometry, FTIR and NMR spectroscopies. T g for this telechelic PCL that was reacted with a small fraction of TEOS increases relative to hydroxy-telechelic PCL due to formation of phase-linking Si–O–Si bonds through end groups. The temperature/magnitude of the melting transition decreased upon inorganic modification. TGA showed appreciable increase in T d relative to PCL and both the high and low temperature degradation processes were hindered. Silane–telechelic PCL films have oxygen permeability values less than that of pure PCL, which is totally attributed to a decrease in diffusion coefficient.

Environmental degradation of biodegradable polyesters 1. Poly(ε-caprolactone), poly[(R)-3-hydroxybutyrate], and poly(L-lactide) films in controlled static seawater

Films of biodegradable aliphatic polyesters, poly(ε-caprolactone) (PCL), poly[(R)-3-hydroxybutyrate] (R-PHB), and poly(L-lactide) (PLLA) were prepared by solution-casting and annealing from the melt. Their biodegradation in static seawater controlled at 25 °C was investigated using polarizing optical microscopy, gravimetry, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and tensile testing. The change in weight loss, tensile strength, and Young's modulus revealed that the biodegradabilities of the aliphatic polyesters in the controlled seawater decreased in the order: PCL>R-PHB>PLLA. The results of gravimetry, GPC, and DSC showed that the biodegradation of PCL and R-PHB films proceeds via surface erosion mechanisms. The polarizing optical microscopy indicated that the PCL and R-PHB films were biodegraded inhomogeneously on the film surface where the marine microbes attached, resulting in pore formation. The crystalline residues of PCL and R-PHB films could not be traced by GPC even when large weight losses occurred. Polarizing optical microscopy and GPC indicated that the decreased tensile strength and Young's modulus of the PCL and R-PHB films are attributed to the formation of pores and cracks during biodegradation. The biodegradation of the PLLA films was insignificant even after immersion in the controlled seawater for 10 weeks and the initial crystallinity had no significant effects on the biodegradability of the PLLA films, excluding the tensile properties change. The biodegradation of these aliphatic polyester films in the controlled static seawater could not be traced by GPC and DSC measurements.

Environmental degradation of biodegradable polyesters 2. Poly( ε-caprolactone), poly[(R)-3-hydroxybutyrate], and poly(L-lactide) films in natural dynamic seawater

The (bio)degradation of aliphatic polyesters, poly( ε-caprolactone) (PCL), poly[(R)-3-hydroxybutyrate] (R-PHB), and poly(L-lactide) (PLLA) films in natural dynamic seawater was investigated using polarizing optical microscopy, gravimetry, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and tensile testing. The results were compared with those reported for the polyester films biodegraded in the controlled static seawater to reveal the physical effects in the natural dynamic seawater on the degradation of the aliphatic polyesters. The gravimetry and tensile testing showed that the mechanical stresses and strains in the natural dynamic seawater caused mechanical destruction or degradation of the films, resulting in seemingly accelerated (bio)degradation of all the films compared with that in the controlled static seawater. Such mechanical acceleration effects in the natural dynamic seawater were higher for the R-PHB and PLLA films with relatively high T g than for the PCL films with relatively low T g, when their (bio)degradation was monitored by gravimetry. The polarizing microscopy showed that the R-PHB films were (bio)degraded predominantly at the centers of and between the spherulites. The tensile strength and Young's modulus were lower for the initially crystallized PLLA films than for the initially amorphous PLLA films when compared at the same degradation time.

Enzymatic degradation of blends of poly(ε‐caprolactone) and poly(styrene‐co‐acrylonitrile) by Pseudomonas lipase

AbstractIn polymer blends, the composition and microcrystalline structure of the blend near surfaces can be markedly different from the bulk properties. In this study, the enzymatic degradation of poly(ε‐caprolactone) (PCL) and its blends with poly(styrene‐co‐acrylonitrile) (SAN) was conducted in a phosphate buffer solution containing Pseudomonas lipase, and the degradation behavior was correlated with the surface properties and crystalline microstructure of the blends. The enzymatic degradation preferentially took place at the amorphous part of PCL film. The melt‐quenched PCL film with low crystallinity and small lamellar thickness showed a higher degradation rate compared with isothermally crystallized (at 36, 40, and 44°C) PCL films. Also, there was a vast difference in the enzymatic degradation behavior of pure PCL and PCL/SAN blends. The pure PCL showed 100% weight loss in a very short time (i.e., 72 h), whereas the PCL/SAN blend containing just 1% SAN showed ∼50% weight loss and the degradation ceased, and the blend containing 40% SAN showed almost no weight loss. These results suggest that as degradation proceeds, the nondegradable SAN content increases at the surface of PCL/SAN films and prevents the lipase from attacking the biodegradable PCL chains. This phenomenon was observed even for a very high PCL content in the blend samples. In the blend with low PCL content, the inaccessibility of the amorphous interphase with high SAN content prevented the attack of lipase on the lamellae of PCL. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 868–879, 2002

Biocomposites of non-crosslinked natural and synthetic polymers

Biocomposite films comprising a non-crosslinked, natural polymer (collagen) and a synthetic polymer, poly( ε-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 the1:20 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.

Evaluation of ultra-thin poly(epsilon-caprolactone) films for tissue-engineered skin.

Various natural and synthetic polymeric materials have been used as scaffold matrices for tissue-engineered skin. However, the commercially available skin replacement products pose problems of poor mechanical properties and immunological rejection. We have thus developed a film of 5 microm thickness, via biaxial stretching of poly(epsilon-caprolactone) (PCL), as a potential matrix for living skin replacements. The aim of this study was to evaluate the feasibility of using biaxially stretched PCL films as matrices for culturing human dermal fibroblasts. For this purpose, we cultured human dermal fibroblasts for 7 days on the films. Glass cover slips and polyurethane (PU) sheets were used as controls. The data from phase contrast light, confocal laser, and scanning electron microscopy suggested that biaxially stretched PCL films support the attachment and proliferation of human dermal fibroblasts. Thymidine-labeling results showed quantitatively that cell proliferation on the PCL films was superior to that on the PU samples. These results indicated that biaxially stretched PCL films supported the growth of human dermal fibroblasts and might have potential to be applied in tissue engineering a dermal equivalent or skin graft.

Formation of antibiotic, biodegradable polymers by processing with Irgasan DP300R (triclosan) and its inclusion compound with β‐cyclodextrin

AbstractThe inclusion compound (IC) between the FDA‐approved antibacterial Irgasan DP300 (Trichlosan), and β‐cyclodextrin (CD) has been formed. When the Irgasan–β‐CD–IC is embedded in biodegradeable/bioabsorbable films of poly(ϵ‐caprolactone) (PCL) at low levels (a few wt %), they are rendered resistant to the growth of E. coli bacteria. When these same PCL films embedded with Irgasan–β‐CD–IC are used as the adhesive for laminating cotton fabrics, we observe the resulting cotton laminates to also be resistant to the growth of E. coli bacteria. These results hold promise for the fabrication of bacteria‐resistant polymer films and fibers, as well as antibacterial fabrics, by means of simple melt processing with Irgasan–β‐CD–IC. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 300–309, 2001

Porous biodegradable polyesters. II. Physical properties, morphology, and enzymatic and alkaline hydrolysis of porous poly(ϵ‐caprolactone) films

AbstractPorous poly(ϵ‐caprolactone) (PCL) films were prepared by water extraction of poly(ethylene oxide) (PEO) from their solution‐cast phase‐separated blend films and the dependence of their blend ratio [XPCL = PCL/(PEO + PCL)] and molecular weight of PEO on the porosity, pore size, crystallinity, crystalline thickness, mechanical properties, morphology, and enzymatic and alkaline hydrolysis of the porous PCL films were investigated. The film porosity or extracted weight ratio was in good agreement with the expected values, irrespective of XPCL and molecular weight of PEO. The maximum pore size was larger for the porous films prepared using PEO having a lower molecular weight, compared with films prepared using PEO having a higher molecular weight at the same XPCL. Differential scanning calorimetry of the porous PCL films revealed that their crystallinity and crystalline thickness were almost constant, regardless of XPCL and molecular weight of PEO. The Young's modulus and tensile strength of the porous films decreased, whereas the elongation‐at‐break increased with decreasing XPCL. The enzymatic and alkaline hydrolysis rates of the porous films increased with a decrease in XPCL and an increase in the molecular weight of PEO. The porous PCL films having Young's modulus in the range of 2–24 kg/mm2 and enzymatic hydrolysis rate in the range of one‐ to 20‐fold that of the nonporous PCL film could be prepared by altering XPCL and the molecular weight of PEO. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2281–2291, 2001

Porous Biodegradable Polyesters, 3. Preparation of Porous Poly(ɛ-caprolactone) Films from Blends by Selective Enzymatic Removal of Poly(L-lactide)

Porous poly(e-caprolactone) (PCL) films were prepared by the removal of poly(L-lactide) (PLLA) from phase-separated PLLA/PCL blend films using the selective Proteinase K-catalyzed hydrolysis of PLLA and subsequent elution of its water-soluble oligomers and monomer into the surrounding hydrolysis media. Polarimetry, gravimetry, and differential scanning calorimetry (DSC) confirmed the complete removal of PLLA molecules from the blend films within 5 d of the Proteinase K catalyzed hydrolysis and therefore the formation of porous PCL films when the initial PLLA content [X PLLA(0) (w/w) = PLLA/(PCL + PLLA)] of the blend films was in the range 0.3-0.5. The fragmentation of the blend film with X PLLA(0) 0.7 occurred when the Proteinase K-catalyzed hydrolysis was continued for longer than 5d. These findings exhibited that both the PLLA-rich and PCL-rich phases were continuous in the blend films for X PLLA(0) ranges of 0.3-0.7 and of 0.3-0.5, respectively, and that the PCL rich phase became dispersed when X PLLA(0) was increased to 0,7. The dependence of enzymatic hydrolysis rate on X PLLA(0) strongly suggests that the Proteinase K-catalyzed hydrolysis of the blend films oceurs at the interfaces of PLLA-rich and PCL-rich phases as well as at the film sur faces.

Effects of storage on thermomechanical properties of poly(ɛ-caprolactone) blends containing poly(vinyl pyrrolidone/iodine)

This study reports the effects of: the molecular weight ratio of poly(ɛ-caprolactone) (PCL) in blends containing polymer of high (50 000 g mol-1 ) and low (4000 g mol-1 ) molecular weight; the concentration (0, 1, and 5 wt-%) of poly(vinyl pyrrolidone/iodine) (PVP/I); and storage at 30°C and 75% relative humidity; on the thermomechanical properties of films prepared by solvent evaporation from solutions containing both PCL and PVP/I. The tensile properties were found to be statistically dependent on the molecular weight ratio of PCL but not on the concentration of PVP/I. The reductions in tensile strength and elongation at break associated with increasing amounts of low molecular weight PCL were attributed to a reduction in the concentration of chain entanglements. No changes were observed in viscoelastic properties or the glass transition temperature. Following storage there were no changes in the tensile strength, glass transition temperature, or viscoelastic properties of the films; however, significant reductions in elongation at break were observed. It is suggested that this is due to hydrolytic chain scission of amorphous PCL. Inclusion of 5 wt-% PVP/I increased this process in films containing 100 : 0 and 80 : 20 high/low molecular weight PCL (but not 60 : 40), but the extent of this was small. This study highlighted significant aging properties of PCL in a moist atmosphere. Consequently, it is recommended that suitable packaging materials should be employed to control the exposure of PCL films to water during storage.

Simultaneous biaxial drawing of poly (ϵ-caprolactone) films

The objective in our study was to investigate the biaxial drawing of Poly (ϵ-caprolactone) (PCL), a bioerodable polyester that is flexible and elastomeric. PCL films were fabricated using solution casting and melt-pressing methods, and biaxially drawn to draw ratio of 3×3. The morphology, mechanical properties and gas permeability changes of the undrawn and drawn films were studied. Results showed that even at the low draw ratio used, a fibrillar morphology developed in the films, interspersed with undrawn material. The tensile strengths of the drawn films were also improved by 50–160%. The solution-cast films have higher gas permeabilities (20-fold), with Knudsen flow character, than melt pressed films. This higher gas permeability was attributed to the presence of microvoids and drawing defects. Permeability was reduced in the melt-pressed films and oxygen was found to permeate three times faster than nitrogen. Biaxial drawing increased the gas permeability slightly but selectivity remained unchanged.

Graft polymerisation of acrylamide onto PCL film by electron beam pre-irradiation in air or argon. Morphology in the final grafted state

Poly(ϵ-caprolactone) has been graft polymerised to final graft yields with acrylamide (AAm) as monomer in an aqueous solution by the pre-irradiation method. The synthesis of the samples obtained, pre-irradiated in air or argon atmosphere, was controlled by dose and concentration of inhibitor, provided as Mohr's salt, in the ranges from 2.5 to 10 Mrad and from 0.005 to 0.500 wt%, respectively. Final graft yields and lateral dimensions in swollen condition ranged from 70 to 3400 wt%, and from 23×30 to 89×94 mm 2, respectively, as atmosphere during irradiation, dose and concentration of inhibitor were altered. These properties gave values in crystallinity extending from 4 to 57 wt%. Samples pre-irradiated in air and subsequently graft polymerised yielded higher values of crystallinity in the entire range of dose and concentration of inhibitor. At low concentration of inhibitor, final graft yield and lateral dimension for samples pre-irradiated in air had considerably larger values while the final graft yield and lateral dimension of samples pre-irradiated in argon had slightly larger values at high concentration of inhibitor. The initial biaxial morphology of the PCL film was continuously transformed into a uniform morphology, which was reached at a final graft yield of approximately 800 wt%.

Human articular chondrocyte adhesion and proliferation on synthetic biodegradable polymer films

The effect of polymer chemistry on adhesion, proliferation, and morphology of human articular cartilage (HAC) chondrocytes was evaluated on synthetic degradable polymer films and tissue culture polystyrene (TCPS) as a control. Two-dimensional surfaces of poly(glycolide) (PGA), poly( l-lactide) ( l-PLA), poly( d, l-lactide) ( d, l-PLA), 85:15 poly( d, l-lactide-co-glycolide) ( d, l-PLGA), poly( ε-caprolactone) (PCL), 90:10 ( d, l-lactide-co-caprolactone) ( d, l-PLCL), 9:91 d, l-PLCL, 40:60 l-PLCL, 67:33 poly(glycolide-co-trimethylene carbonate) (PGTMC), and poly(dioxanone) (PDO) were made by spin-casting into uniform thin films. Adhesion kinetics were studied using TCPS and PCL films and revealed that the rate of chondrocyte adhesion began to level off after 6 h. Degree of HAC chondrocyte adhesion was studied on all the substrates after 8 h, and ranged from 47 to 145% of the attachment found on TCPS. The greatest number of chondrocytes attached to PGA and 67:33 PGTMC polymer films, and attachment to PCL and l-PLA films was statistically lower than that found on PGA ( p<0.05). There was no correlation between amount of chondrocyte attachment to the substrates and the substrates’ water contact angle. Chondrocytes proliferated equally well on all the substrates resulting in equivalent cell numbers on all the substrates at both day 4 and day 7 of the culture. However, these total cell numbers were reached as a result of a 88- and 42-fold expansion on PDO and PLA, respectively, which was significantly higher than the 11-fold expansion found on TCPS ( p<0.05). The greater fold expansion of the cells on PDO and l-PLA films may be attributed to the availability of space for cells to grow, since their numbers at the start of culture were fewer following the 8 h attachment period. This suggests that regardless of initial seeding density on these degradable polymer substrates (i.e., if some minimum number of cells are able to attach), they will eventually populate the surfaces of all these polymers given sufficient space and time.

Formation of antibiotic, biodegradable/bioabsorbable polymers by processing with neomycin sulfate and its inclusion compound with ?-cyclodextrin

Samples of pure neomycin sulfate and its inclusion compound (IC) with β-cyclodextrin were implanted into films of poly(L-lactic acid) (PLLA) and poly(e-caprolactone) (PCL). Both polymers have been widely used commercially to make sutures. The antibacterial activity of these films against Escherichia coli was tested. Films made by either solution casting or melt pressing were divided into the following three groups: (1) plain polymer films, (2) those embedded with pure neomycin sulfate, and (3) those embedded with neomycin sulfate-β-cyclodextrin IC. Filter paper treated with 1.5 μL of 10 mg/μL Kanamycin and neomycin were used as controls and resulted in 11- and 8-mm zones of inhibition/or antibacterial activity, respectively. Small discs (ca. 2% of total area) cut from solution-cast films of PLLA and PCL containing 50 wt % neomycin sulfate IC had 17- and 16-mm zones of inhibition, and PLLA and PCL containing 50 wt % pure neomycin sulfate deterred bacterial growth, resulting in 19-mm zones of inhibition. Melt-pressed films containing 10 wt % pure neomycin sulfate or its IC, showed 17- and 11-mm zones of inhibition for PLLA films, respectively, while PCL films showed 13- and 9-mm zones of inhibition, respectively. For melt-pressed films that contain 0.01 wt % pure neomycin sulfate or its IC, PLLA films showed 11- and 9.5-mm zones of inhibition, respectively, while PCL films showed 11- and 10-mm zones of inhibition, respectively. Since an antibiotic, bioabsorbable suture does not require surgical removal, implanting an inclusion compound in the suture might allow the slow release of antibiotic, thereby guarding against postsurgical infection and also protecting the antibiotic from degradation during the melt-spinning process used to make the suture. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 937–947, 1999

Effect of molecular orientation on the biodegradability of aliphatic polyester

AbstractThe effect of morphological microstructure on the biodegradability of aliphatic polyester, poly(ϵ ‐caprolactone) (PCL) was studied in terms of crystallite size, crystallinity and amorphous and crystalline orientation factors. Microstructural changes during hydrolysis/biodegradation of the drawn PCL films were investigated by the conventional small and wide angle X‐ray scattering methods. The lower was the draw ratio, the higher the hydrolytic degradability or biodegradability. With the increase of the hydrolysis time, the long period, at earlier stage, decreased; then slightly recovered and the crystallinity increased while the lamellar thickness remained unchanged. The amorphous orientation factors start to decrease at earlier stage and gradually go down to zero before the end of hydrolysis. In the case of crystalline orientation factor, although the values decrease with increasing hydrolysis time, they do not reach zero point. After the biodegradation for 60 days, crystallinity, crystal lateral size and lamellar thickness in all drawn PCL films decreased, and then it was confirmed that even crystalline regions were degraded for long term biodegradation test.

A novel laser light-scattering study of enzymatic biodegradation of poly(ε-caprolactone) nanoparticles

A successful micronization of water-insoluble poly(ε-caprolactone) (PCL) into narrowly distributed nanoparticles stable in water has not only enabled us to study the enzymatic biodegradation of PCL in water at 25°C by a combination of static and dynamic laser light scattering (LLS), but also to shorten the biodegradation time by a factor of more than 10 3 compared with using a thin PCL film, i.e. a 1 week conventional experiment becomes a 4 min one. The time-average scattering intensity decreased linearly. It was interesting to find that the decrease of the scattering intensity was not accompanied by a decrease of the average size of the PCL nanoparticles, indicating that the enzyme, Lipase Pseudomonas (PS), “eats” the PCL nanoparticles one-by-one, so that the biodegradation rate is determined mainly by the enzyme concentration. Moreover, we found that using anionic sodium lauryl sulphate instead of cationic hexadecyltrimethylammonium bromide as surfactant in the micronization can prevent the biodegradation, suggesting that the biodegradation involves two essential steps: the adsorption of slightly negatively charged Lipase PS onto the PCL nanoparticles and the interaction between Lipase PS and PCL.