Biodegradable electrospun fibers for drug delivery

Nanofibrous Sugar Sticks Electrospun from Glycopolymers for Protein Separation via Molecular Recognition

Summary: Nanofibrous sugar sticks with linear PANCGAMA and cyclic PANCAG glucose pendants were fabricated by electrospinning from acrylonitrile‐based glycopolymers. Field emission scanning electron microscope was used to characterize the morphologies of the nanofibers. Utilizing the specific carbohydrate‐protein interaction, these two kinds of nanofiber mats were applied to separate the protein mixtures. Con A and BSA were used as model proteins. The Con A/BSA mixture solution was isolated successfully by selective adsorption of Con A to the cyclic glucose pendants on the PANCAG nanofibrous sugar sticks. However, PANCGAMA nanofibers showed almost no selectivity for these two proteins due to the poor specificity between linear glucose pendants and Con A.

Modulation of protein release from biodegradable core–shell structured fibers prepared by coaxial electrospinning

Biodegradable core-shell structured fibers with poly(epsilon-caprolactone) as shell and bovine serum albumin (BSA)-containing dextran as core were prepared by coaxial electrospinning for incorporation and controlled release of proteins. BSA loading percent in the fibers and its release rate could be conveniently varied by the feed rate of the inner dope during electrospinning. With the increase in the feed rate of the inner dope, there was an associated increase in the loading percent and accelerated release of BSA. Poly(ethylene glycol) (PEG) was added to the shell section of the fibers to further finely modulate the release behavior of BSA. It was revealed that the release rate of BSA increased with the PEG percent in the shell section. By varying the feed rate of the inner dope and PEG content, most of BSA could be released from the core-shell structured fibers within the period of time ranging from 1 week to more than 1 month. The effect of the feed rate of the inner dope and addition of PEG into the shell section on the fiber morphology was also examined by scanning electron microscope.

Melt electrospinning of poly-(ethylene glycol-block-ε-caprolactone)

Various block copolymers of poly(ethylene glycol) and poly(epsilon-caprolactone) (PEG-b-PCL) with molecular weights between 7000 and 26,900 g/mol were synthesized, and melt electrospun at temperatures between 60 degrees C and 90 degrees C. Two types of fibers were collected, including excellent quality fibers - highly coiled and continuous, with a constant diameter and relatively defect free. Such fibers, termed "solid fibers", were sufficiently cooled during their path between the spinneret and the collector that the symmetric fiber shape is maintained after landing on the collector. The second type of melt electrospun fiber were poor quality, large diameter fibers, flattened on the collector - termed "molten fibers". The solid and molten fibers were morphologically distinct from each other as determined from scanning electron microscopy (SEM). Using an SEM imaging method to assess the regional variations of collected electrospun material, we found the spinneret pump rate largely influenced the fiber quality. The polymer flow rate to the spinneret and the molecular weight of PEG-b-PCL had the greatest effect on the electrospun fibers collected, with an optimum rate of 0.05-0.1 mL/h for the highest molecular weight copolymers. The lowest molecular weight PEG-b-PCL tended to electrospray, while the material collected from higher molecular weight copolymers were conducive to fiber formation. The highest quality fibers were PEG-b-PCL block copolymers (22,000 and 26,900 g/mol) melt electrospun at temperatures of 85 degrees C and 90 degrees C, corresponding to shear viscosities of the polymer of between 28.1 and 39.4 Pa.S.

Mechanical properties of single electrospun drug-encapsulated nanofibres

The mechanical and structural properties of a surface play an important role in determining the morphology of attached cells, and ultimately their cellular functions. As such, mechanical and structural integrity are important design parameters for a tissue scaffold. Electrospun fibrous meshes are widely used in tissue engineering. When in contact with electrospun scaffolds, cells see the individual micro- or nanofibres as their immediate microenvironment. In this study, tensile testing of single electrospun nanofibres composed of poly(ε-caprolactone) (PCL), and its copolymer, poly(caprolactone-co-ethyl ethylene phosphate) (PCLEEP), revealed a size effect in the Young's modulus, E, and tensile strength, σ(T). Both strength and stiffness increase as the fibre diameter decreases from bulk (∼5 μm) into the nanometre region (200-300 nm). In particular, E and σ(T) of individual PCL nanofibres were at least two-fold and an order of magnitude higher than that of PCL film, respectively. PCL films were observed to have more pronounced crystallographic texture than the nanofibres; however no difference in crystalline fraction, perfection, or texture was detected among the various fibres. When drugs were encapsulated into single PCLEEP fibres, mechanical properties were enhanced with 1-20 wt% of loaded retinoic acid, but weakened by 10-20 wt% of encapsulated bovine serum albumin. This understanding of the effect of size and drug and protein encapsulation on the mechanical properties of electrospun fibres may help in the optimization of tissue scaffold design that combines biochemical and biomechanical cues for tissue regeneration.

Encapsulating drugs in biodegradable ultrafine fibers through co-axial electrospinning

This article describes an electrospinning process to fabricate double-layered ultrafine fibers. A bioabsorbable polymer, Polycaprolactone (PCL), was used as the outer layer or the shell and two medically pure drugs, Resveratrol (RT, a kind of antioxidant) and Gentamycin Sulfate (GS, an antibiotic), were used as the inner layers or the cores. Morphology and microstructure of the ultrafine fibers were characterized by scanning electron microscope (SEM) and transmission electron microscopy (TEM), whereas mechanical performance of them was understood through tensile test. In vitro degradation rates of the nanofibrous membranes were determined by measuring their weight loss when immersed in pH 7.4 phosphate-buffered saline (PBS) mixed with certain amount of Pseudomonas lipase for a maximum of 7 days. The drug release behaviors of the RT and GS were measured using a high performance liquid chromatography (HPLC) and ultraviolet-visible (UV-vis) spectroscopy, respectively. It has been found that the drug solutions without any fiber-forming additive could be encapsulated in the PCL ultrafine fibers, although they alone cannot be made into a fiber form. Beads on the fiber surface influenced the tensile behavior of the ultrafine fibers remarkably. When the core solvent was miscible with the shell solvent, higher drug concentration decreased the bead formation and thus favored the mechanical performance. The situation, however, became different if the two solvents were immiscible with each other. The degradation rate was closely related to hydrophilicity of the drugs in the cores. Higher hydrophilicity apparently led to faster degradation. The release profiles of the RT and GS exhibited a sustained release characteristic, with no burst release phenomenon.

Improvement of cell adhesion on poly(L-lactide) by atmospheric plasma treatment

The purpose of this study is to elucidate the interaction between the cell and the surface of poly(L-lactide) (PLLA) samples, which were modified using a low-temperature plasma treatment apparatus at atmospheric pressure. The plasma treatments were carried out in the atmospheres of air, carbon dioxide (CO2), and perfluoro propane (C3F8) gas. The PLLA samples before and after the plasma treatment were analyzed by XPS and their contact angles with water. Furthermore, the cell adhesion capability and cell mass culturing tests on the PLLA samples were carried out using MC3T3-E1 cells. The results showed that the contact angle of the samples, which was plasma treated in air or in CO2 gas, decreased compared with that of the untreated samples. On the other hand, the contact angle of the samples, which was plasma treated in the C3F8 gas, increased compared with the untreated plasma samples. The cell response on the PLLA samples plasma treated in air or in the CO2 gas were significantly superior to that of the PLLA samples, which was plasma treated in the C3F8 gas.

Electrospun Micro- and Nanofibers for Sustained Delivery of Paclitaxel to Treat C6 Glioma in Vitro

PURPOSE

The present study aims to develop electrospun PLGA-based micro- and nanofibers as implants for the sustained delivery of anticancer drug to treat C6 glioma in vitro.

METHODS

PLGA and an anticancer drug--paclitaxel-loaded PLGA micro- and nanofibers were fabricated by electrospinning and the key processing parameters were investigated. The physical and chemical properties of the micro- and nanofibers were characterized by various state-of-the-art techniques, such as scanning electron microscope and field emission scanning electron microscope for morphology, X-ray photoelectron spectroscopy for surface chemistry, gel permeation chromatogram for molecular weight measurements and differential scanning calorimeter for drug physical status. The encapsulation efficiency and in vitro release profile were measured by high performance liquid chromatography. In addition, the cytotoxicity of paclitaxel-loaded PLGA nanofibers was evaluated using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide MTT) assay on C6 glioma cell lines.

RESULTS

PLGA fibers with diameters of around several tens nanometers to 10 microm were successfully obtained by electrospinning. Ultrafine fibers of around 30 nm were achieved after addition of organic salts to dilute polymer solution. The encapsulation efficiency for paclitaxel-loaded PLGA micro- and nanofibers was more than 90%. DSC results suggest that the drug was in the solid solution state in the polymeric micro- and nanofibers. In vitro release profiles suggest that paclitaxel sustained release was achieved for more than 60 days. Cytotoxicity test results suggest that IC50 value of paclitaxel-loaded PLGA nanofibers (36 microg/ml, calculated based on the amount of paclitaxel) is comparable to the commercial paclitaxel formulation-Taxol.

CONCLUSIONS

Electrospun paclitaxel-loaded biodegradable micro- and nanofibers may be promising for the treatment of brain tumour as alternative drug delivery devices.

BCNU-loaded PEG-PLLA ultrafine fibers and their in vitro antitumor activity against Glioma C6 cells

The purpose of the present study was to develop implantable BCNU-loaded poly(ethylene glycol)-poly(L-lactic acid) (PEG-PLLA) diblock copolymer fibers for the controlled release of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). BCNU was well incorporated and dispersed uniformly in biodegradable PEG-PLLA fibers by using electrospinning method. Environmental Scanning Electron Microscope (ESEM) images indicated that the BCNU-loaded PEG-PLLA fibers looked uniform and their surfaces were reasonably smooth. Their average diameters were below 1500 nm. The release rate of BCNU from the fiber mats increased with the increase of BCNU loading amount. In vitro cytotoxicity assay showed that the PEG-PLLA fibers themselves did not affect the growth of rat Glioma C6 cells. Antitumor activity of the BCNU-loaded fibers against the cells was kept over the whole experiment process, while that of pristine BCNU disappeared within 48 h. These results strongly suggest that the BCNU/PEG-PLLA fibers have an effect of controlled release of BCNU and are suitable for postoperative chemotherapy of cancers.

Synthesis and characterization of RGD peptide grafted poly(ethylene glycol)-b-poly(L-lactide)-b-poly(L-glutamic acid) triblock copolymer

Advances in tissue engineering require biofunctional scaffolds that can provide not only physical support for cells but also chemical and biological cues needed in forming functional tissues. To achieve this goal, a novel RGD peptide grafted poly(ethylene glycol)-b-poly(L-lactide)-b-poly(L-glutamic acid) (PEG-PLA-PGL/RGD) was synthesized in four steps (1) to prepare diblock copolymer PEG-PLA-OH and to convert its -OH end group into -NH(2) (to obtain PEG-PLA-NH(2)), (2) to prepare triblock copolymer PEG-PLA-PBGL by ring-opening polymerization of NCA (N-carboxyanhydride) derived from benzyl glutamate with diblock copolymer PEG-PLA-NH(2) as macroinitiator, (3) to remove the protective benzyl groups by catalytic hydrogenation of PEG-PLA-PBGL to obtain PEG-PLA-PGL, and (4) to react RGD (arginine-glycine-(aspartic amide)) with the carboxyl groups of the PEG-PLA-PGL. The structures of PEG-PLA-PGL/RGD and its precursors were confirmed by (1)H NMR, FT-IR, amino acid analysis, and XPS analysis. Addition of 5 wt % PEG-PLA-PGL/RGD into a PLGA matrix significantly improved the surface wettability of the blend films and the adhesion and proliferation behavior of human chondrocytes and 3T3 cells on the blend films. Therefore, the novel RGD-grafted triblock copolymer is expected to find application in cell or tissue engineering.

Biodegradable Heparin-Loaded Microspheres: Carrier Molecular Composition and Microsphere Structure

Microspheres of amphiphilic triblock polymers PLLA-PEG-PLLA were investigated as carriers for heparin delivery. Two series of PLLA-PEG-PLLA triblock were synthesized and prepared into microspheres with heparin loaded. The microspheres were hollow and the surface morphology varied from smooth to porous. The pore size increased with increasing PEG content. The microsphere size distribution showed that higher PEG content increased the average microsphere size. The release rate of heparin was closely related to the surface morphology of the microspheres. DSC spectra showed that both cold crystalline temperature (Tc) and crystalline melting temperature (Tm) of heparin-loaded microspheres were related to the copolymer composition and the Tc was lower than those of corresponding pure microspheres. [IMAGES: SEE TEXT]

Investigation of Drug Release and Matrix Degradation of Electrospun Poly(dl-lactide) Fibers with Paracetanol Inoculation

This study was aimed at assessing the potential use of electrospun fibers as drug delivery vehicles with focus on the different diameters and drug contents to control drug release and polymer fiber degradation. A drug-loaded solvent-casting polymer film was made with an average thickness of 100 microm for comparative purposes. DSC analysis indicated that electrospun fibers had a lower T(g) but higher transition enthalpy than solvent-casting polymer film due to the inner stress and high degree of alignment and orientation of polymer chains caused by the electrospinning process. Inoculation of paracetanol led to a further slight decrease in the T(g) and transition enthalpy. An in vitro drug release study showed that a pronounced burst release or steady release phase was initially observed followed by a plateau or gradual release during the rest time. Fibers with a larger diameter exhibited a longer period of nearly zero order release, and higher drug encapsulation led to a more significant burst release after incubation. In vitro degradation showed that the smaller diameter and higher drug entrapment led to more significant changes of morphologies. The electrospun fiber mat showed almost no molecular weight reduction, but mass loss was observed for fibers with small and medium size, which was characterized with surface erosion and inconsistent with the ordinarily polymer degrading form. Further wetting behavior analysis showed that the high water repellent property of electrospun fibers led to much slower water penetration into the fiber mat, which may contribute to the degradation profiles of surface erosion. The specific degradation profile and adjustable drug release behaviors by variation of fiber characteristics made the electrospun nonwoven mat a potential drug delivery system rather than polymer films and particles.

Electrospinning of Polymeric Nanofibers for Tissue Engineering Applications: A Review

Interest in electrospinning has recently escalated due to the ability to produce materials with nanoscale properties. Electrospun fibers have been investigated as promising tissue engineering scaffolds since they mimic the nanoscale properties of native extracellular matrix. In this review, we examine electrospinning by providing a brief description of the theory behind the process, examining the effect of changing the process parameters on fiber morphology, and discussing the potential applications and impacts of electrospinning on the field of tissue engineering.

Coaxial Electrospinning of (Fluorescein Isothiocyanate-Conjugated Bovine Serum Albumin)-Encapsulated Poly(ε-caprolactone) Nanofibers for Sustained Release

As an aim toward developing biologically mimetic and functional nanofiber-based tissue engineering scaffolds, we demonstrated the encapsulation of a model protein, fluorescein isothiocyanate-conjugated bovine serum albumin (fitcBSA), along with a water-soluble polymer, poly(ethylene glycol) (PEG), within the biodegradable poly(epsilon-caprolactone) (PCL) nanofibers using a coaxial electrospinning technique. By variation of the inner flow rates from 0.2 to 0.6 mL/h with a constant outer flow rate of 1.8 mL/h, fitcBSA loadings of 0.85-2.17 mg/g of nanofibrous membranes were prepared. Variation of flow rates also resulted in increases of fiber sizes from ca. 270 nm to 380 nm. The encapsulation of fitcBSA/PEG within PCL was subsequently characterized by laser confocal scanning microscopy, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analysis. In vitro release studies were conducted to evaluate sustained release potential of the core-sheath-structured composite nanofiber PCL-r-fitcBSA/PEG. As a negative control, composite nanofiber PCL/fitcBSA/PEG blend was prepared from a normal electrospinning method. It was found that core-sheath nanofibers PCL-r-fitcBSA/PEG pronouncedly alleviated the initial burst release for higher protein loading and gave better sustainability compared to that of PCL/fitcBSA/PEG nanofibers. The present study would provide a basis for further design and optimization of processing conditions to control the nanostructure of core-sheath composite nanofibers and ultimately achieve desired release kinetics of bioactive proteins (e.g., growth factors) for practical tissue engineering applications.

Hydrophilic nanofibrous structure of polylactide; fabrication and cell affinity

Microstructure and architecture of the scaffolds along with the surface chemistry exert profound effect on biological activity (cell distribution, proliferation, and differentiation). For the biological activity, scaffolds in tissue engineering have been widely designed. The objective of this study was to develop hydrophilic nanofibrous structure of polylactides (PLLA) polymer in the form of nonwoven mat by electrospinning technique, and further evaluate the fibroblast NIH3T3 cell proliferation, morphology, and cell-matrix interaction. Hydrophilicity of the PLLA fibers was improved by adding small fraction of low molecular weight polyethylene glycol (PEG) into the electrospinning solution. Four different ratio types (100/0, 80/20, 70/30, and 50/50) of PLLA/PEG electrospun matrices were fabricated, and the pore characteristics, tensile properties, contact angle, and hydrolytic degradation were observed. Furthermore, scanning electron microscope (SEM) and fluorescence actin staining images were used for micro-observation of cell-matrix interaction and cell morphology. It was found that the electrospun mat of PLLA/PEG (80/20), composed of fibers with diameters in the range 540-850 nm, majority of pore diameter less than 100 microm, tensile strength 8 MPa, elongation 150%, porosity more than 90%, and improved hydrophilicity with slow hydrolytic degradation, is favorable for biological activity of NIH3T3 fibroblast cell. Based on these results, the correct composition of PLLA and PEG in the porous electrospun matrix (i.e., PLLA/PEG (80/20)) will be a better candidate rather than other compositions of PLLA/PEG as well as hydrophobic PLLA for application in tissue engineering.

The role of electrospinning in the emerging field of nanomedicine

The fact that in vivo the extracellular matrix (ECM) or substratum with which cells interact often includes topography at the nanoscale underscores the importance of investigating cell-substrate interactions and performing cell culture at the submicron scale. An important and exciting direction of research in nanomedicine would be to gain an understanding and exploit the cellular response to nanostructures. Electrospinning is a simple and versatile technique that can produce a macroporous scaffold comprising randomly oriented or aligned nanofibers. It can also accommodate the incorporation of drug delivery function into the fibrous scaffold. Endowed with both topographical and biochemical signals such electrospun nanofibrous scaffolds may provide an optimal microenvironment for the seeded cells. This review covers the analysis and control of the electrospinning process, and describes the types of electrospun fibers fabricated for biomedical applications such as drug delivery and tissue engineering.

Controlled release of heparin from poly(epsilon-caprolactone) electrospun fibers

Sustained delivery of heparin to the localized adventitial surface of grafted blood vessels has been shown to prevent the vascular smooth muscle cell (VSMC) proliferation that can lead to graft occlusion and failure. In this study heparin was incorporated into electrospun poly(epsilon-caprolactone) (PCL) fiber mats for assessment as a controlled delivery device. Fibers with smooth surfaces and no bead defects could be spun from polymer solutions with 8%w/v PCL in 7:3 dichloromethane:methanol. A significant decrease in fiber diameter was observed with increasing heparin concentration. Assessment of drug loading, and imaging of fluorescently labeled heparin showed homogenous distribution of heparin throughout the fiber mats. A total of approximately half of the encapsulated heparin was released by diffusional control from the heparin/PCL fibers after 14 days. The fibers did not induce an inflammatory response in macrophage cells in vitro and the released heparin was effective in preventing the proliferation of VSMCs in culture. These results suggest that electrospun PCL fibers are a promising candidate for delivery of heparin to the site of vascular injury.

Sustained release of proteins from electrospun biodegradable fibers

Electrospinning is a simple and versatile technique of producing polymeric fibers ranging from submicron to micron in diameter. Incorporation of bioactive agents into the fibers could make a biofunctional tissue engineering scaffold. In this study, we investigated the feasibility of encapsulating human beta-nerve growth factor (NGF), which was stabilized in a carrier protein, bovine serum albumin (BSA) in a copolymer of epsilon-caprolactone and ethyl ethylene phosphate (PCLEEP) by electrospinning. Partially aligned protein encapsulated fibers were obtained and the protein was found to be randomly dispersed throughout the electrospun fibrous mesh in aggregate form. A sustained release of NGF via diffusion process was obtained for at least 3 months. PC12 neurite outgrowth assay confirmed that the bioactivity of electrospun NGF was retained, at least partially, throughout the period of sustained release, thus clearly demonstrating the feasibility of encapsulating proteins via electrospinning to produce biofunctional tissue scaffolds.

In vitro non-viral gene delivery with nanofibrous scaffolds

Extracellular and intracellular barriers typically prevent non-viral gene vectors from having an effective transfection efficiency. Formulation of a gene delivery vehicle that can overcome the barriers is a key step for successful tissue regeneration. We have developed a novel core-shelled DNA nanoparticle by invoking solvent-induced condensation of plasmid DNA (beta-galactosidase or GFP) in a solvent mixture [94% N,N-dimethylformamide (DMF) + 6% 1x TE buffer] and subsequent encapsulation of the condensed DNA globule in a triblock copolymer, polylactide-poly(ethylene glycol)-polylactide (L8E78L8), in the same solvent environment. The polylactide shell protects the encapsulated DNA from degradation during electrospinning of a mixture of encapsulated DNA nanoparticles and biodegradable PLGA (a random copolymer of lactide and glycolide) to form a nanofibrous non-woven scaffold using the same solution mixture. The bioactive plasmid DNA can then be released in an intact form from the scaffold with a controlled release rate and transfect cells in vitro.

A facile technique to prepare biodegradable coaxial electrospun nanofibers for controlled release of bioactive agents

A one-step, mild procedure based on coaxial electrospinning was developed for incorporation and controlled release of two model proteins, BSA and lysozyme, from biodegradable core-shell nanofibers with PCL as shell and protein-containing PEG as core. The thickness of the core and shell could be adjusted by the feed rate of the inner dope, which in turn affected the release profiles of the incorporated proteins. It was revealed that the released lysozyme maintained its structure and bioactivity. The current method may find wide applications for controlled release of proteins and tissue engineering.

Ultrafine medicated fibers electrospun from W/O emulsions

Ultrafine fibers containing water-soluble drugs were successfully electrospun from water-in-oil (W/O) emulsions, in which the aqueous phase contained the water-soluble drugs and the oily phase was a chloroform solution of amphiphilic poly (ethylene glycol)-poly (L-lactic acid) (PEG-PLLA) diblock copolymer. The diameter of the electrospun fibers was in the range of 300 nm-1 microm. A water-soluble anticancer agent, doxorubicin hydrochloride (Dox), was used as the model drug. Its content in the fibers was 1-5 wt.% and it was entirely encapsulated inside the electrospun fibers. Its release from the fibers was controlled by the combined diffusion mechanism and enzymatic degradation mechanism. At the early stage, the diffusion mechanism was predominant and a certain time later, the enzymatic degradation mechanism became predominant. The antitumor activity of the Dox incorporated in the PEG-PLLA fibers against mice glioma cells (C6 cell lines) was evaluated by MTT method. The results showed that the Dox could be released from the fibers without losing cytotoxicity.

Recent development of polymer nanofibers for biomedical and biotechnological applications

Research in polymer nanofibers has undergone significant progress in the last one decade. One of the main driving forces for this progress is the increasing use of these polymer nanofibers for biomedical and biotechnological applications. This article presents a review on the latest research advancement made in the use of polymer nanofibers for applications such as tissue engineering, controlled drug release, wound dressings, medical implants, nanocomposites for dental restoration, molecular separation, biosensors, and preservation of bioactive agents.

Characterization of the Surface Biocompatibility of the Electrospun PCL-Collagen Nanofibers Using Fibroblasts

The effect of nanofiber surface coatings on the cell's proliferation behavior was studied. Individually collagen-coated poly(epsilon-caprolactone) (PCL) nanofibers (i.e., Collagen-r-PCL in the form of a core-shell structure) were prepared by a coaxial electrospinning technique. A roughly collagen-coated PCL nanofibrous matrix was also prepared by soaking the PCL matrix in a 10 mg/mL collagen solution overnight. These two types of coated nanofibers were then used to investigate differences in biological responses in terms of proliferation and cell morphology of human dermal fibroblasts (HDF). It was found that coatings of collagen on PCL nanofibrous matrix definitely favored cells proliferation, and the efficiency is coating means dependent. As compared to PCL, the HDF density on the Collagen-r-PCL nanofiber membrane almost increased linearly by 19.5% (2 days), 22.9% (4 days), and 31.8% (6 days). In contrast, the roughly collagen-coated PCL increased only by 5.5% (2 days), 11.0% (4 days), and 21.0% (6 days). SEM observation indicated that the Collagen-r-PCL nanofibers encouraged cell migration inside the scaffolds. These findings suggest that the Collagen-r-PCL nanofibers can be used as novel functional biomimetic nanofibers toward achieving excellent integration between cells and scaffolds for tissue engineering applications.

A composite of hydroxyapatite with electrospun biodegradable nanofibers as a tissue engineering material

Biodegradable and biocompatible poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a copolymer of microbial polyester, was fabricated as a nanofibrous film by electrospinning and composited with hydroxyapatite (HAp) by soaking in simulated body fluid. Compared with a PHBV cast (flat) film, the electrospun PHBV nanofibrous film was hydrophobic. However, after HAp deposition, both of the surfaces were extremely hydrophilic. The degradation rate of HAp/PHBV nanofibrous films in the presence of polyhydroxybutyrate depolymerase was very fast. Nanofiber formation increased the specific surface area and HAp enhanced the invasion of enzyme into the film by increasing surface hydrophilicity. The surface of the nanofibrous film showed enhanced cell adhesion over that of the flat film, although cell adhesion was not significantly affected by the combination with HAp.

Influence of the drug compatibility with polymer solution on the release kinetics of electrospun fiber formulation

The electrospun fiber mat for drug delivery is a novel formulation with promising clinical applications in the future. The influence of the solubility and compatibility of drugs in the drug/polymer/solvent system on the encapsulation of the drug inside the poly(L-lactide) (PLLA) electrospun fibers and the release behavior of this formulation were examined by using paclitaxel, doxorubicin hydrochloride and doxorubicin base as model drugs. The burst release of the drugs can be avoided by using compatible drugs with polymers, and the drug release can follow nearly zero-order kinetics due to the degradation of the PLLA fibers in the presence of proteinase K.

Development of novel tissue engineering scaffolds via electrospinning

Electrospinning has recently been developed as an efficient technique to develop polymeric nanofibres. Various synthetic and natural biodegradable polymers have been electrospun into fibres with diameters in the nanometre range (< 1 microm). The fibre diameter, structure and physical properties of the nanofibre matrices can be effectively tuned by controlling various parameters that affect the electrospinning process. The dimension and structure of electrospun polymeric nanofibre mats resembles mostly the collagen phase of natural extracellular matrix. This, combined with excellent physical properties such as high surface area, high porosity, interconnective pores of the nanofibre matrices and appropriate mechanical properties, well-controlled degradation rates and biocompatibility of the base polymer, make biodegradable polymeric nanofibre matrices ideal candidates for developing scaffolds for tissue engineering. This article reviews the recent advances in the development of synthetic biodegradable nanofibre-based matrices as scaffolds for tissue engineering.

Use of monoatomic and polyatomic projectiles for the characterisation of polylactic acid by static secondary ion mass spectrometry

The application of polyatomic primary ions is a strongly developing branch of static secondary ion mass spectrometry (S-SIMS), since these projectiles allow a significant increase in the secondary ion yields to be achieved. However, the different limitations and possibilities of certain polyatomic primary ions for use on specific functional classes of samples are still not completely known. This paper compares the use of monoatomic and polyatomic primary ions in S-SIMS for thin layers of polylactic acid (PLA), obtained by spin-coating solutions on silicon wafers. Bombardment with Ga+, Xe+ and SF5+ primary ions allowed the contribution of the projectile mass and number of atoms in the gain in ion yield and molecular specificity (relative importance of high m/z and low m/z signals) to be assessed. Samples obtained by spin-coating solutions with increasing concentration showed that optimal layer thickness depended on the primary ion used. In comparison with the use of Ga+ projectiles, the yield of structural ions increased by a factor of about 1.5 to 2 and by about 7 to 12 when Xe+ and SF5+ primary ion bombardment were applied, respectively. A detailed fragmentation pattern was elaborated to interpret ion signal intensity changes for different projectiles in terms of energy deposition and collective processes in the subsurface, and the internal energy of radical and even-electron precursor ions.

Nanofibres and their Influence on Cells for Tissue Regeneration

Synthetic polymer and biopolymer nanofibres can be fabricated through self-assembly, phase separation, electrospinning, and mechanical methods. These novel functional biocompatible polymers are very promising for a variety of future biomedical applications. There are many characteristics of nanofibres that would potentially influence cell growth and proliferation. As such, many studies have been carried out to elucidate the cell–nanofibre interaction with the purpose of optimizing the matrix for cell growth and tissue regeneration. In this Review, we present current literatures and our research on the interactions between cells and nanofibres, and the potentials of nanofibre scaffolds for biomedical applications.

Enzymatic Degradation of Poly(L-lactide) and Poly(?-caprolactone) Electrospun Fibers

Poly(L-lactide) (PLLA) and poly(epsilon-caprolactone) (PCL) ultrafine fibers were prepared by electrospinning. The influence of cationic and anionic surfactants on their enzymatic degradation behavior was investigated by measuring weight loss, molecular weight, crystallinity, and melting temperature of the fibers as a function of degradation time. Under the catalysis of proteinase K, the PLLA fibers containing the anionic surfactant sodium docecyl sulfate (SDS) exhibited a faster degradation rate than those containing cationic surfactant triethylbenzylammonium chloride (TEBAC), indicating that surface electric charge on the fibers is a critical factor for an enzymatic degradation. Similarly, TEBAC-containing PCL fibers exhibited a 47% weight loss within 8.5 h whereas SDS-containing PCL fibers showed little degradation in the presence of lipase PS. By analyzing the charge status of proteinase K and lipase PS under the experimental conditions, the importance of the surface charges of the fibers and their interactions with the charges on the enzymes were revealed. Consequently, a "two-step" degradation mechanism was proposed: (1) the enzyme approaches the fiber surface; (2) the enzyme initiates hydrolysis of the polymer. By means of differential scanning calorimetry and wide-angle X-ray diffraction, the crystallinity and orientation changes in the PLLA and PCL fibers during the enzymatic degradation were investigated, respectively.