Development of a slow non-viral DNA release system from PDLLA scaffolds fabricated using a supercritical CO2 technique.
ABSTRACT Polyamidoamine polymers (PAA) comprising methylene-bisacrylamide/dimethylethylene-diamine monomers were synthesized, complexed with DNA and incorporated into porous P(DL)LA scaffolds by using a supercritical CO(2) (scCO(2)) technique. Scaffolds were made in a dry state consequently there was a need to lyophilize the complexes. A statistically significant reduction of the transfection efficiency was observed in the absence of trehalose when compared to the original complex after freeze-drying. Increasing concentrations (0-10% w/v) of trehalose were added to the complex prior to freeze-drying. Structure dependent differences in DNA binding were evaluated by gel electrophoresis and thermal transition analysis. TEM and PCS showed aggregate formation after freeze-drying without trehalose. Scaffolds were characterized by pore sizes of 173 +/- 73 microm and a porosity of 71%. The transfection potential of the released DNA was investigated by seeding scaffolds with A549 cells and following firefly luciferase as a marker gene after 48 h exposure. Low but continuous levels of transfection were observed for PAA complexes during a 60-day study. Complexes made with Lipofectaminetrade mark gave initially higher levels of DNA release but no further expression was seen after 40 days. Uncomplexed DNA showed background levels of transfection. Culturing cells on 3D scaffolds showed a benefit in retention of transfection activity with time compared to 2D controls. Transfection levels could be increased when cells were grown in OptiMEM. This study demonstrated that PAA/DNA complexes incorporated into a P(DL)LA scaffold made by using scCO(2) processing exhibited a slow release and extended gene expression profile.
- [Show abstract] [Hide abstract]
ABSTRACT: The aim of this study was to prepare poly-DL-lactide/polyethylene glycol (PDLLA/PEG) blends to improve medium absorption and cell proliferation in the three-dimensional (3-D) structure of their scaffolds. Carbon dioxide (CO2) was used as a foaming agent to create porosity in these blends. The results of Fourier transform infrared (FTIR) spectroscopy demonstrated that the blends were homogeneous mixtures of PDLLA and PEG. The peak shifts at 1092 and 1744 cm(-1) confirmed the presence of molecular interactions between these two compounds. Increasing the PEG weight ratio enhanced the relative crystallinity and hydrophilicity. The PDLLA/PEG blends (especially 80/20 and 70/30 weight ratios) exhibited linear degradation profiles over an incubation time of 8 weeks. The mechanical properties of PDLLA/PEG blends having less than 30 wt.% PEG were suitable for the fabrication of porous scaffolds. Increasing the concentration of PEG to above 50% resulted in blends that were brittle and had low mechanical integrity. Highly porous scaffolds with controllable pore size were produced for 30 wt.% PEG samples using the gas foaming technique at temperatures between 25 and 55 °C and pressures between 60 and 160 bar. The average pore diameters achieved by gas foaming process were between 15 and 150 μm, and had an average porosity of 84%. The medium uptake and degradation rate of fabricated PDLLA/PEG scaffolds were increased compared with neat PDLLA film due to the presence of PEG and porosity. The porous scaffolds also demonstrated a lower modulus of elasticity and a higher elongation at break compared to the non-porous film. The fabricated PDLLA/PEG scaffolds have high potential for various tissue-engineering applications.Acta biomaterialia 02/2012; 8(2):570-8. · 5.09 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: A novel nano-structured polyaniline-ionic liquid (i.e. 1-butyl-3-methylimidazolium hexafluorophosphate, BMIPF(6)) composite (BPAN) film coated steel wire was prepared by electrochemical deposition. Scanning electron microscopy images showed that the obtained porous BPAN coating consisted of nanofibers, whose diameter ranged from 50 to 80 nm. Furthermore, the novel nano-structured composite coating was very stable at relatively high temperatures (up to 350 °C) and it could be used for more 250 times without obvious decrease of the extraction efficiency. The novel BPAN coating was used for the headspace solid-phase microextraction (HS-SPME) of organochlorine pesticides (i.e. hexachlorocyolohexane, dichlorodiphenyldichloroethylene, dichlorodiphenyldichloroethane, dichlorodiphenyltrichloroethane), coupled with gas chromatography-electron capture detection (GC-ECD). The BPAN coating showed better analytical capability on the whole compared with common polyaniline (PANI) and polydimethylsiloxane (PDMS) coatings. The key parameters influencing extraction efficiency were investigated and optimized, including desorption time, stirring speed, extraction temperature, extraction time and ionic strength. The relative standard deviations (RSDs) for single fiber repeatability ranged from 2.3 to 8.7% (n=6) and the RSDs for fiber-to-fiber reproducibility (n=6) were 4.2-12.1%, respectively. The linear ranges exceeded three magnitudes with correlation coefficients above 0.99. The detection limits were 0.12-0.31 ng L(-1). The proposed method was successfully applied for the determination of organochlorine pesticides in lake water, waste water and sewage treatment plant effluent with good recoveries from 88.9 to 112.9%.Journal of Chromatography A 07/2011; 1218(37):6285-91. · 4.61 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Introduction: Next-generation scaffolds for bone tissue engineering (BTE) should exhibit the appropriate combination of mechanical support and morphological guidance for cell proliferation and attachment while at the same time serving as matrices for sustained delivery of therapeutic drugs and/or biomolecular signals, such as growth factors. Drug delivery from BTE scaffolds to induce the formation of functional tissues, which may need to vary temporally and spatially, represents a versatile approach to manipulating the local environment for directing cell function and/or to treat common bone diseases or local infection. In addition, drug delivery from BTE is proposed to either increase the expression of tissue inductive factors or to block the expression of others factors that could inhibit bone tissue formation. Composite scaffolds which combine biopolymers and bioactive ceramics in mechanically competent 3D structures, including also organic-inorganic hybrids, are being widely developed for BTE, where the affinity and interaction between biomaterials and therapeutic drugs or biomolecular signals play a decisive role in controlling the release rate. Areas covered: This review covers current developments and applications of 3D composite scaffolds for BTE which exhibit the added capability of controlled delivery of therapeutic drugs or growth factors. A summary of drugs and biomolecules incorporated in composite scaffolds and approaches developed to combine biopolymers and bioceramics in composites for drug delivery systems for BTE is presented. Special attention is given to identify the main challenges and unmet needs of current designs and technologies for developing such multifunctional 3D composite scaffolds for BTE. Expert opinion: One of the major challenges for developing composite scaffolds for BTE is the incorporation of a drug delivery function of sufficient complexity to be able to induce the release patterns that may be necessary for effective osseointegration, vascularization and bone regeneration. Loading 3D scaffolds with different biomolecular agents should produce a codelivery system with different, predetermined release profiles. It is also envisaged that the number of relevant bioactive agents that can be loaded onto scaffolds will be increased, whilst the composite scaffold design should exploit synergistically the different degradation profiles of the organic and inorganic components.Expert Opinion on Drug Delivery 06/2013; · 4.87 Impact Factor