|Articles about Biomaterials|
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| Photochemical crosslinking improves the physicochemical properties of collagen scaffolds
Chan, B. P. and K. F. So (2005), J Biomed Mater Res A 75(3): 689-701.
Abstract: Collagen is a natural biomaterial with excellent biocompatibility. However, unprocessed collagen has low stability and weak mechanical strength, which limits its application in tissue engineering. The current study aimed to improve the physicochemical properties of collagen scaffolds by using photochemical crosslinking. Collagen gel was reconstituted and photochemically crosslinked by using laser irradiation in the presence of a photosensitizer. Scanning electron microscope was used to characterize the surface and cross-sectional morphology. Stress-strain relationship and other mechanical properties were determined by uniaxial tensile tests. Thermostability and water-binding capacities also were analyzed by using differential scanning calorimetry and swelling ratio measurements, respectively. Photochemically crosslinked porous structures showed fine microstructure with interconnected micron-sized pores, whereas uncrosslinked controls only showed macrosheet-like structures. The stabilizing effect of photochemical crosslinking also was revealed by retaining the three-dimensional lamellae-like structures after thermal analysis in crosslinked membranes but not in the controls. Photochemical crosslinking also significantly reduced the swelling ratio, improved the stress-strain relationship, peak load, ultimate stress, rupture strain, and tangent modulus of collagen membranes. The current study showed that an innovative photochemical crosslinking process was able to produce collagen scaffolds with fine microstructures; to strengthen, stiffen, and stabilize collagen membranes; and to modify their swelling ratio. This may broaden the use of collagen-based scaffolds in tissue engineering, particularly for weight-bearing tissues. (c) 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005.
| Photocrosslinking characteristics and mechanical properties of diethyl fumarate/poly(propylene fumarate) biomaterials
Fisher, J. P., D. Dean, et al. (2002), Biomaterials 23(22): 4333-43.
Abstract: The development of tissue engineered materials for the treatment of large bone defects would provide attractive alternatives to the autografts, allografts, non-degradable polymers, ceramics, and metals that are currently used in clinical settings. To this end, poly(propylene fumarate) (PPF), a viscous polyester synthesized from diethyl fumarate (DEF), has been studied for use as an engineered bone graft. We have investigated the photocrosslinking of PPF dissolved in its precursor, DEF, using the photoinitiator bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (BAPO) and low levels of ultraviolet light exposure. A three factor, 2 x 2 x 4 factorial design was developed, studying the effects of PPF number average molecular weight, BAPO initiator content, and DEF content upon photocrosslinking characteristics and mechanical properties. Uncured DEF/PPF solution viscosity fell over three orders of magnitude as DEF content was increased from 0% to 75%. The exothermic photocrosslinking reaction released low levels of heat, with no more than 160J/g released from any formulation tested. As a result, the maximum photocrosslinking temperature remained below 47 degrees C for all samples. Both sol fraction and swelling degree generally increased with increasing DEF content. Compressive mechanical properties were within the range of trabecular bone, with the strongest samples possessing an elastic modulus of 195.3 +/- 17.5 MPa and a fracture strength of 68.8 +/- 9.4MPa. Finally, the results indicate that PPF crosslinking was facilitated at low DEF precursor concentrations, but hindered at higher precursor concentrations. These novel DEF/PPF solutions may be preferred over pure PPF as the basis for an engineered bone graft because they (1) exhibit reduced viscosity and thus are easily handled, (2) form polymer networks with compressive strength at fracture suitable for consideration for trabecular bone replacement, and (3) may be readily fabricated into solids with a wide range of structures.
| Photocurable hard and porous biomaterials from ROMP precursors cross-linked with diyl radicals
Enholm, E., A. Joshi, et al. (2005), Bioorg Med Chem Lett 15(23): 5262-5.
Abstract: A combination of (ROMP) ring-opening metathesis polymerization and diradical (diyl) cross-linking provides a new access to hard biomaterials and potential artificial bone replacements. ROMP was used to construct soft and pliable linear polymers bearing photolabile diazene functions. After treatment with light, a nitrogen aerosol is released throughout the polymer to create desirable porosity, cross-linking, and hardening in a single step. Nonpolymeric mechanistic work supporting these studies was also examined.
| Photodegradation of DDT with the photodeposited ferric ion on the TiO2 film
Jang, S. J., M. S. Kim, et al. (2005), Water Res 39(10): 2178-88.
Abstract: The photodegradation capability of DDT has been enhanced by Fe/TiO2 film in a photoreactor with UV radiation. The optimal thickness of TiO2 for the DDT photodegradation was 2.94 microm with a 3-time coating, where the first-order rate constant was 0.077 min(-1). The optimal Fe3+(ferric ion) photodeposition amount was estimated as 3.7 x 10(-4) mg mm(-2) corresponding with 0.73 mg Fe3+ (mg TiO2)(-1). Photoremoval rate of DDT increased with an increasing pH value, while the pH value of solution decreased to acidic region during the DDT photodegradation. The photodegradation efficiency was 85% in 20 min with only TiO2 film and increased from 85% up to 96% by the photodeposition of 0.73 mg Fe3+ (mg TiO2)(-1) on TiO2 film as a sensitizer since the band gap energy of Fe2O3 (2.2 eV) is lower than that of TiO2 (3.0 eV).
| Photoenhancement of platelet adhesion to biomaterial surfaces observed with epifluorescent video microscopy (EVM)
Haycox, C. L., B. D. Ratner, et al. (1991), J Biomed Mater Res 25(10): 1317-20.
| Photoimmobilisation of poly(N-vinylpyrrolidinone) as a means to improve haemocompatibility of polyurethane biomaterials
Wetzels, G. M. and L. H. Koole (1999), Biomaterials 20(20): 1879-87.
Abstract: A novel method to improve the haemocompatibility of polymeric biomaterials (in particular: polyurethane elastomers) is reported. The new approach essentially rests upon photochemical immobilisation of the highly biocompatible polymer poly(N-vinylpyrrolidinone) (poly(NVP)) onto the biomaterial's surface. One of the key steps in the surface modification procedure is the preparation of a copolymer of NVP and the photoreactive building block 4-[4'-azidobenzoyl]-oxo-n-butylmethacrylate (1). This copolymer is first dissolved in a volatile solvent, then sprayed onto the biomaterial's surface, and subsequently immobilised via irradiation with ultraviolet light. The paper describes: (i) preparation of 1, (ii) preparation of the copolymer (NVP + 1), (iii) physico-chemical characterisation of the modified surfaces, and (iv) results of two in vitro haemocompatibility assays (i.e. thrombin generation and adhesion of blood platelets from recalcified human platelet-rich plasma). Furthermore, the surface modification was performed with a microporous polyurethane vascular graft (Chronoflex), which is already in clinical use. The in vitro experiments revealed that significant improvement of the haemocompatibility of polyurethanes can be achieved through this method.
| Photo-immobilization of dipyridamole (Persantin) at the surface of polyurethane biomaterials: reduction of in-vitro thrombogenicity
Aldenhoff, Y. B., R. Blezer, et al. (1997), Biomaterials 18(2): 167-72.
Abstract: Dipyridamole is a well-known vasodilator and a powerful inhibitor of activation and aggregation of blood platelets. Moreover, dipyridamole is essentially non-toxic. The drug is used extensively in clinical anti-coagulation regimes, for example pre- and post-coronary angioplasty procedures. Recently, we have found that photochemical, covalent coupling of dipyridamole to polyurethane surfaces leads to improved thromboresistance in vitro. This phenomenon is now studied in more detail. Both qualitative and more quantitative biochemical experiments were performed in order to characterize the in vitro blood compatibility of a set of polyurethane surfaces onto which dipyridamole was immobilized. First, scanning electron microscopy was used to examine the morphology of platelets which adhered during incubation with platelet-rich plasma. These experiments showed that immobilization of dipyridamole leads to a clearly decreased number of adherent platelets and to a largely diminished propensity of the surface to activate adherent platelets. Secondly, an in vitro thrombogenicity assay was run. These experiments showed that the thromboresistance increased with increasing surface density of immobilized dipyridamole. A short spacer chain separating dipyridamole from the polymer surface, was found to improve the thromboresistance further. Such a spacer chain apparently increases the efficacy of the immobilized drug. Collectively, the present results further substantiate the idea that dipyridamole retains its inhibitory activity with respect to activation and aggregation of blood platelets, when the compound is covalently attached to a polymer surface. The possible utility of these findings with respect to the development of an artificial blood vessel prosthesis is discussed briefly.
| Photoinduced plasticity in cross-linked polymers
Scott, T. F., A. D. Schneider, et al. (2005), Science 308(5728): 1615-7.
Abstract: Chemically cross-linked polymers are inherently limited by stresses that are introduced by post-gelation volume changes during polymerization. It is also difficult to change a cross-linked polymer's shape without a corresponding loss of material properties or substantial stress development. We demonstrate a cross-linked polymer that, upon exposure to light, exhibits stress and/or strain relaxation without any concomitant change in material properties. This result is achieved by introducing radicals via photocleavage of residual photoinitiator in the polymer matrix, which then diffuse via addition-fragmentation chain transfer of midchain functional groups. These processes lead to photoinduced plasticity, actuation, and equilibrium shape changes without residual stress. Such polymeric materials are critical to the development of microdevices, biomaterials, and polymeric coatings.
| Photopolymerized biomaterials for application in the temporomandibular joint
Poshusta, A. K. and K. S. Anseth (2001), Cells Tissues Organs 169(3): 272-8.
Abstract: Chronic foreign body reactions have limited the successful application of alloplastic implants for treatment of temporomandibular joint (TMJ) disorders. There is a great clinical need for new materials with enhanced properties for application in the diarthrodial joint. Photopolymerizations may provide many advantages for fabricating new biomaterials for the TMJ and may address some of the notable differences between the TMJ and other articulations. Specifically, the feasibility of trans-tissue (i.e. through the skin) photopolymerizations may yield less-invasive surgical procedures. Also, novel 3-dimensional photoprocessing techniques may be used to fabricate patient-specific alloplastic devices for improved compliance and efficacy. Finally, the mild conditions necessary for photopolymerizations make the reaction ideal for encapsulating cells with the potential to create constructs for tissue engineering, which may be beneficial for disk replacement therapies.
| Photoreactive analog of peptide FN-C/H-V from the carboxy-terminal heparin-binding domains of fibronectin supports endothelial cell adhesion and spreading on biomaterial surfaces
Huebsch, J. B., G. B. Fields, et al. (1996), J Biomed Mater Res 31(4): 555-67.
Abstract: The extracellular matrix protein fibronectin (FN) plays an important role in cell adhesion, spreading, and motility. Several cell-adhesion promoting domains exist within fibronectin, and peptide sequences from these domains have been shown to play an important role in cell interactions with fibronectin. Recently, a peptide sequence (FN-C/H-V) from the 33/66 kD carboxy-terminal heparin-binding domains of fibronectin was shown to promote the adhesion and spreading of vascular endothelial cells in vitro. Endothelial cell spreading on this peptide was followed by cytoskeletal reorganization, focal contact formation, and, ultimately, cell migration. In the current study, a photoreactive analog of FN-C/H-V (ASD-V) was generated using a heterobifunctional photoreactive crosslinking agent, sulfosuccinimidyl 2-(pazidosalicylamido) ethyl-1,3'-dithio-propionate. ASD-V was then covalently coupled to polystyrene (PS) and polyethylene terephthalate film (PET) in order to assess the utility of ASD-V for preparing biomaterial surfaces with endothelial cell-adhesion promoting properties. The effects of pre-adsorption time and initial coating concentration on the efficiency of ASD-V coupling to PS and to PET were examined. Contact angle measurements and atomic force microscopy were used to characterize ASD-V-modified surfaces. Finally, the adhesion and spreading of vascular endothelial cells on ASD-V-modified surfaces was assessed. Our results suggest that photoreactive peptides are an effective and convenient means of modifying biomaterial surfaces to impart adhesion-promoting properties and that ASD-V, when coupled to PS and PET, promotes endothelial cell adhesion and spreading and may therefore be useful as a biomaterial surface modification in applications where re-endothelialization is desired (e.g., autologous endothelial seeding of vascular grafts, or transplantation of genetically engineered endothelial cells via polymer-coated stents.
| Photosensitized oxidation of biomaterials and related model compounds
Davila, J. and A. Harriman (1989), Photochem Photobiol 50(1): 29-35.
Abstract: Aluminium trisulfonatophthalocyanine (A1PCS), a dye being widely advocated for use in photodynamic therapy, produces singlet oxygen with a quantum yield of 0.34 in oxygenated water at pH 7. Triplet A1PCS abstracts an electron from a variety of amines and phenols, the rate of electron transfer depending upon the thermodynamic driving force, forming the A1PCS radical anion. This latter species reduces molecular oxygen to superoxide ions with high efficiency. The triplet state also abstracts an electron from biological components, including NADH, vitamin C, cysteine, methionine, tyrosine, tryptophan, uracil, and guanine, but not from DNA. These results suggest that photoinduced electron abstraction from appropriate biomaterials could compete with singlet oxygen production under in vivo conditions.
| pH-sensitive polyelectrolyte complex gel microspheres composed of chitosan/sodium tripolyphosphate/dextran sulfate: swelling kinetics and drug delivery properties
Lin, W. C., D. G. Yu, et al. (2005), Colloids Surf B Biointerfaces 44(2-3): 143-51.
Abstract: Porous chitosan (CS) polyelectrolyte complex (PEC) hydrogel microspheres were prepared via either wet phase-inversion or ionotropic crosslinking with sodium tripolyphosphate (Na+ - TPP) and dextran sulfate (DS). The resulting microspheres were characterized using scanning electron microscopy (SEM) and elemental analysis (EA). The controlled release behavior of ibuprofen (IBU) from these microspheres was investigated. The PEC microspheres were about 700-950 microm in diameter with large pores and open porous structure. The CS/TPP/DS microspheres resisted hydrolysis in strong acid and biodegradation in enzymatic surroundings. The swelling kinetics for CS microspheres was close to Fickian diffusion, whereas those for CS/TPP and CS/TPP/DS were non-Fickian. Furthermore, the equilibrium water content (EWC) and water diffusion coefficient (D) increased with the pH of the media. The release profiles of IBU from CS/TPP/DS microspheres were slow in simulated gastric fluid (SGF, pH 1.4) over 3 h, but nearly all of the initial drug content was released in simulated intestinal fluid (SIF, pH 6.8) within 6 h after changing media. Overall the results demonstrated that CS/TPP/DS microspheres could successfully deliver a hydrophobic drug to the intestine without losing the drug in the stomach, and hence could be potential candidates as an orally administered drug delivery system.
| Physical and biological characteristics of the main biomaterials used in pelvic surgery
Brun, J. L., L. Bordenave, et al. (1992), Biomed Mater Eng 2(4): 203-25.
Abstract: Our study compared mechanical and biological properties of four materials classically used in surgery: polyethylene terephtalate (Mersilene), polypropylene (Marlex), polytetrafluoroethylene (Teflon) and expanded one (Gore-Tex) and polyaramide (Kevlar). No deterioration for polytetrafluoroethylene and polypropylene under irradiation was observed when materials were treated by physical means. Mechanical tests showed that all these materials could bear more than 50 N. Such a high tensile strength is never reached in visceral physiology. Results of graft elongation during tensile strength test shows two classes: a first one that includes high elongation grafts (Gore-Tex and Marlex) and a second one that includes low elongation grafts (Mersilene and Kevlar). As these materials have many potential uses in surgery, we have performed cytotoxicity tests. Material extracts were obtained under standardized conditions, and we have looked at a potentially toxic effect of substances eventually leached from the materials towards cells cultured in vitro. None of the material extracts listed above were cytotoxic except for untreated Kevlar. Toxicity disappeared when Kevlar was treated with methanol. As suspected, untreated Kevlar contains toxic additives introduced during the manufacture of this textile. Thus, in spite of good mechanical properties, Kevlar should not be used in pelvic surgery on account of its lower bicompatibility. These results shows that the choice of the grafts by surgeons must be relevant in a given application.
| Physical and biological properties of a novel siloxane adhesive for soft tissue applications
Wilson, D. J., D. H. Chenery, et al. (2005), J Biomater Sci Polym Ed 16(4): 449-72.
Abstract: The aim of this study was to investigate the adhesive properties of an in-house aminopropyltrimethoxysilane-methylenebisacrylamide (APTMS-MBA) siloxane system and compare them with a commercially available adhesive, n-butyl cyanoacrylate (nBCA). The ability of the material to perform as a soft tissue adhesive was established by measuring the physical (bond strength, curing time) and biological (cytotoxicity) properties of the adhesives on cartilage. Complementary physical techniques, X-ray photoelectron spectroscopy, Raman and infrared imaging, enabled the mode of action of the adhesive to the cartilage surface to be determined. Adhesion strength to cartilage was measured using a simple butt joint test after storage in phosphate-buffered saline solution at 37 degrees C for periods up to 1 month. The adhesives were also characterised using two in vitro biological techniques. A live/dead stain assay enabled a measure of the viability of chondrocytes attached to the two adhesives to be made. A water-soluble tetrazolium assay was carried out using two different cell types, human dermal fibroblasts and ovine meniscal chondrocytes, in order to measure material cytotoxicity as a function of both supernatant concentration and time. IR imaging of the surface of cartilage treated with APTMS-MBA siloxane adhesive indicated that the adhesive penetrated the tissue surface marginally compared to nBCA which showed a greater depth of penetration. The curing time and adhesion strength values for APTMS-MBA siloxane and nBCA adhesives were measured to be 60 s/0.23 MPa and 38 min/0.62 MPa, respectively. These materials were found to be significantly stronger than either commercially available fibrin (0.02 MPa) or gelatin resorcinol formaldehyde (GRF) adhesives (0.1 MPa) (P < 0.01). Cell culture experiments revealed that APTMS-MBA siloxane adhesive induced 2% cell death compared to 95% for the nBCA adhesive, which extended to a depth of approximately 100-150 microm into the cartilage surface. The WST-1 assay demonstrated that APTMS-MBA siloxane was significantly less cytotoxic than nBCA adhesive as an undiluted conditioned supernatant (P < 0.001). These results suggest that the APTMS-MBA siloxane may be a useful adhesive for medical applications.
| Physical factors affecting kinesin-based transport of synthetic nanoparticle cargo
Bachand, M., A. M. Trent, et al. (2005), J Nanosci Nanotechnol 5(5): 718-22.
Abstract: Recently, kinesin biomolecular motors and microtubules filaments (MTs) were used to transport metal and semiconductor nanoparticles with the long-term goal of exploiting this active transport system to dynamically assemble nanostructured materials. In some cases, however, the presence of nanoparticle cargo on MTs was shown to inhibit transport by interfering with kinesin-MT interactions. The primary objectives of this work were (1) to determine what factors affect the ability of kinesin and MTs to transport nanoparticle cargo, and (2) to establish a functional parameter space in which kinesin and MTs can support unimpeded transport of nanoparticles and materials. Of the factors evaluated, nanoparticle density on a given MT was the most significant factor affecting kinesin-based transport of nanoparticles. The density of particles was controlled by limiting the number of available linkage sites (i.e., biotinylated tubulin), and/or the relative concentration of nanoparticles in solution. Nanoparticle size was also a significant factor affecting transport, and attributed to the ability of particles < 40 nm in diameter to bind to the "underside" of the MT, and block kinesin transport. Overall, a generalized method of assembling and transporting a range of nanoparticle cargo using kinesin and MTs was established.
| Physical properties and biocompatibility of chitosan/soy blended membranes
Silva, S. S., M. I. Santos, et al. (2005), J Mater Sci Mater Med 16(6): 575-9.
Abstract: Blends of polysaccharides and proteins are a source for the development of novel materials with interesting and tailorable properties, with potential to be used in a range of biomedical applications. in this work a series of blended membranes composed by chitosan and soy protein isolate was prepared by solvent casting methodology. in addition, cross-linking was performed in situ with glutaraldehyde solutions in the range 5x10(-3)-0.1 M. Furthermore, the influence of the composition and cross-linking on the degradation behaviour, water uptake and cell adhesion was investigated. The obtained results showed that the incorporation of chitosan, associated to network formation by cross linking, promoted a slight decrease of water absorption and a slower degradability of the membranes. Moreover, direct contact biocompatibility studies, with L929 cells, indicate that the cross-linking enhances the capability of the material to support cell growth.
| Physical, mechanical and degradation properties, and schwann cell affinity of cross-linked chitosan films
Cao, W., M. Cheng, et al. (2005), J Biomater Sci Polym Ed 16(6): 791-807.
Abstract: Three kinds of cross-linked chitosan films were prepared with hexamethylene diisocyanate (HDI), epichlorohydrin (ECH) and glutaraldehyde (GA) as cross-linking agents, respectively. The physical and mechanical properties, biodegradability and Schwann cell affinity of the cross-linked films were investigated. A significant decrease in the degradation rate in lysozyme solution and a large change in the mechanical properties were observed compared with non-cross-linked chitosan films. The protein adsorption on chitosan films was determined by means of enzyme-linked immunosorbent assay (ELISA). In comparison with the non-cross-linked films, the chitosan films cross-linked with HDI showed a significant increase (up to 40-50%) in both fibronectin and laminin adsorption, while the protein adsorption on the other two kinds of cross-linked films was similar to that on non-crosslinked films. In addition, cell culture revealed that the HDI cross-linked chitosan films enhanced the spread and proliferation of Schwann cells while the other cross-linked films delayed the cell proliferation. These results suggest that HDI cross-linking of chitosan films provides a combination of physical properties, biodegradability and Schwann cell affinity suitable for peripheral nerve regeneration.
| Physicochemical characterisation and biological evaluation of hydrogel-poly(epsilon-caprolactone) interpenetrating polymer networks as novel urinary biomaterials
Jones, D. S., D. W. McLaughlin, et al. (2005), Biomaterials 26(14): 1761-70.
Abstract: Hydrogels are frequently employed as medical device biomaterials due to their advantageous biological properties, e.g. resistance to infection and encrustation, biocompatibility; however, their poor mechanical properties generally limit the scope of application to coatings of medical devices. To address this limitation, this study described the formulation of sequential interpenetrating polymer networks (IPN) of poly(-caprolactone) (PCL) and poly(hydroxyethylmethacrylate) (p(HEMA)). IPN containing 20% w/w PCL, p(HEMA), both in the presence or absence of ethyleneglycol dimethacrylate (EGDMA 1% w/w), were prepared by free radical polymerisation. Following preparation the degradation and the mechanical and surface properties of the biomaterials and, in addition, the resistances to microbial adherence and encrustation in vitro were examined. In comparison to p(HEMA) the various IPN exhibited substantially greater tensile properties (ultimate tensile strength, % elongation, Young's modulus) that were accredited to the discrete distribution of PCL within the hydrogel network. The IPN exhibited two glass transition temperatures that were statistically similar to those of the individual components, thereby providing evidence of the immiscible nature of the two polymers. The IPN possessed higher receding contact angles and lower equilibrium water contents in comparison to p(HEMA), whereas the limited degradation of the IPN at both pH 7 and 9 was deemed suitable for clinical usage for periods of at least 4 weeks. The resistances of the various IPN to bacterial adherence and urinary encrustation were examined using in vitro models. Importantly the resistance of the IPN to encrustation was, in general, similar to that of p(HEMA) but greater than that of PCL whereas, the resistance of the IPN to bacterial adherence was frequently greater than that of p(HEMA) and PCL. Therefore, this study has shown that the mechanical properties of p(HEMA) may be substantially increased by the formation of IPN with PCL whilst maintaining other appropriate physicochemical properties and resistances to urinary encrustation and bacterial adherence. It is suggested that these IPN may be suitable for device fabrication thereby expanding the manufacturing application of hydrogels without compromising their potential clinical efficacy.
| Physicochemical characterization of poly(L-lactic acid) and poly(D,L-lactide-co-glycolide) nanoparticles with polyethylenimine as gene delivery carrier
Kim, I. S., S. K. Lee, et al. (2005), Int J Pharm 298(1): 255-62.
Abstract: Polymer nanoparticles have been used as non-viral gene delivery systems and drug delivery systems. In this study, biodegradable poly(L-lactic acid) (PLA)/polyethylenimine (PEI) and poly(D,L-lactide-co-glycolide) (PLGA)/PEI nanoparticles were prepared and characterized as gene delivery systems. The PLA/PEI and PLGA/PEI nanoparticles, which were prepared by a diafiltration method, had spherical shapes and smooth surface characteristics. The size of nanoparticles was controlled by the amount of PEI, which acted as a hydrophilic moiety, which effectively reduced the interfacial energy between the particle surface and the aqueous media. The nanoparticles showed an excellent dispersive stability under storage in a phosphate-buffered saline solution for 12 days. The positive zeta-potentials for the nanoparticles decreased and changed to negative values with increasing plasmid DNA (pDNA) content. Agarose gel electrophoresis showed that the complex formation between the nanoparticles and the pDNA coincided with the zeta-potential results. The results of in vitro transfection and cell viability on HEK 293 cells indicated that the nanoparticles could be used as gene delivery carriers.
| Physicochemical characterizations of self-assembled nanoparticles of glycol chitosan-deoxycholic acid conjugates
Kim, K., S. Kwon, et al. (2005), Biomacromolecules 6(2): 1154-8.
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