Physicochemical and biological properties of nanohydroxyapatite grafted with star-shaped poly(ε-caprolactone).

To overcome the disadvantages generated by the lack of interfacial bonding between hydroxyapatite nanocrystals (HAPN) and agglomeration of particles in the development of biodegradable nanocomposites a chemical grafting method was applied to modify the surface of HAPN through grafting of the three-arms star-shaped poly(ε-caprolactone) (SPCL) onto the nanoparticles. The chemical grafting of SPCL onto HAPN (SPCL-g-HAPN) has been investigated using Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy (TEM), photoelectron spectroscopy, X-ray diffraction, zeta potential (ZP) and contact angle (CA). TEM micrographs of the SPCL-g-HAPN revealed the existence of hybrid organic/inorganic (O/I) nanoscale domains. The results of albumin (HSA) and fibrinogen (HFb) adsorption indicate resistance to HFb adsorption by SPCL-g-HAPN relatively to unmodified HAPN. The ZP and CA measurement suggest a heterogeneous topology for SPCL-g-HAPN likely due to the existence of hydrophobic-hydrophilic regions on the nanocomposite surface. The enzyme degradation by cholesterol esterase and lipase indicates that the rates of hydrolysis for SPCL-g-HAPN were very slow relative to the SPCL/HAPN blends. The in vitro biological studies showed that the human osteoblast-like cells (MG-63) cells had normal morphology and they were able to attach and spread out on SPCL-g-HAPN surfaces. A higher overall cellular proliferation was observed on SPCL-g-HAPN scaffolds compared to pure HAPN or SPCL materials.

In vitro cytotoxic data on Se-methylselenocysteine conjugated to dendritic poly(glycerol) against human squamous carcinoma cells.

Polymeric nanoparticles acting as sources of selenium (Se) are currently an interesting topic in cancer chemotherapy. In this study, polyglycerol dendrimer (DPGLy) was functionalized with seleno-methyl-selenocysteine (SeMeCys) by means of Steglich esterification with 4-dimethylaminopyridine/(l-ethyl-3-(3-dimethylaminopropyl)carbodiimide) (EDC/DMAP) and cerium chloride as cocatalyst in acetonitrile at quantitative yields of 98 ± 1%. The SeMeCys coupling DPGLy efficiency vs. time were determined by Fourier Transform infrared spectroscopy (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy. The cytotoxic effects of SeMeCys-DPGLy on the Chinese Hamster ovary cell line (CHO-K1) and head and neck squamous cell carcinoma (HNSCC) cells line were assessed by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. No signs of general toxicity of SeMeCys-DPGLy against CHO-K1 cells were detectable at which cell viability was greater than 98%. MTS assays revealed that SeMeCys-DPGLy reduced HNSCC cell viability and proliferation at higher doses and long incubation times.

Microfluidic caging lipase in hyperbranched polyglycerol microcapsules for extracorporeal treatment of enzyme pancreatic insufficiency.

Lipase cartridges are currently the mainstay of treatment to improve fat absorption related to pancreatic insufficiency (PI) in patients receiving enteral nutrition feedings. Enzyme immobilization is an essential prerequisite for designing lipase cartridges systems for efficient enzymatic fat hydrolysis. A microfluidic approach has been adopted to produce lipase (LIP) caged in hyperbranched polyglycerol microcapsules (HPGly). The resulting HPGly-LIP microcapsules are spherical and had an average diameter of 29 µm with monomodal size distribution. The optimum conditions determined by artificial neural networks were HPGly concentration of 10 wt.%, LIP loading of 20% (wt) and total flow rate in microfluidic cell of 1.0 mL/h. Under these conditions, the maximum capacity of the LIP that can be microencapsulated is around 85% with respect to the HPGly concentration of 10 wt.% and total flow rate in microfluidic cell of 1.0 mL/h. This resultant HPGly-LIP exhibited Michaelis-Menten coefficients of 1.138,14 mM (Km) and 0.49 U/mg (Vmax) showing higher activity compared to free LIP. Finally, the robust HPGly-LIP microcapsules showed excellent recyclability. The in vitro Analysis of the HPGly-LIP cytotoxicity showed that microcapsules had no cytotoxic effect to L929 fibroblasts cells and behaved very similar to the negative control. These features will be useful for the facile construction of biocatalytic systems with high efficiency, excellent recyclability and adequate biocompatibility for treatment of patients with PI receiving enteral nutrition feedings.

Long term multiple sclerosis drug delivery using dendritic polyglycerol flower-like microspheres.

The purpose of this study was to produce and characterize the dendritic polyglycerol microspheres (DPGlyM) carrier with potential for use in the treatment of multiple sclerosis (MS). This novel drug delivery system is comprised of DPGlyM as carrier for dimethyl fumarate (DMF) and curcumin (CUR). Molecular docking (MD) was used as in-silico tool to guide the drug entrapment and indicates a spontaneous interactions of DPGlyM with DMF (ΔG° = -11.3 kJ mol-1) and CUR (ΔG° = -23.8 kJ mol-1). The DPGlyM morphology and size distribution were determined using a scanning electron microscopy (SEM). The average size of the microspheres was 30-40 µm. The highest encapsulation efficiency and loading efficiency for CUR and DMF were 94.1% and 65.3%, respectively. The zeta potential indicates that CUR and DMF loaded DPGlyM form stable suspension in phosphate buffer solution (PBS) at pH 7.4. Cytotoxicity and hemocompatibility studies suggest that CUR and DMF loaded DPGlyM not influenced cell viability and are well tolerated in hemolysis assays without any damaging effects even at high concentrations up to 50 mg/mL. The in-vitro release of DMF and CUR in phosphate buffer of pH 7.4 followed a kinetics type super case II transport. The activation energy for CUR and DMF release from DPGlyM was found to be 56.95 kJ/mol and 13.87 kJ/mol for CUR and DMF, respectively. The in vitro release assays show that the DPGlyM has good sustained release of CUR and DMF for 5 days. CUR and DMF loaded DPGlyM have shown promising results for a sustained release during enhanced time duration.

Biological properties of electrospun cellulose scaffolds from biomass.

Nowadays the development of sustainable technologies for the effective production of polymeric materials that can be used as biomaterials will be of importance. In this work, cellulose (CEL) was purified from potato peel waste (PPW) and used to produce electrospun nanofibers for tissue engineering applications. The purified CEL was solubilized in copper ethylenediamine (Cuen) and the electrospun nanofibers was produced through electrospinning technique in diameter range of 250-500 nm at electrical field strength of 20 kV. To confirm the applicability of the electrospun CEL scaffolds in tissue engineering, in vitro BALB-3T3 fibroblastic cell adhesion and cell proliferation tests were employed in this study. Cell viability was evaluated by staining with ethidium bromide (EtBr) and acridine orange (AO) to evaluate the possible effects of cytotoxicity of the CNF scaffolds. Fluorescence studies confirmed that BALB-3T3 viable cells attached and spread throughout the CEL scaffold. The attachment and spreading of viable cells suggests that electrospun CEL scaffolds support growth of BALB-3T3 fibroblasts cells and suggests that PPW can be a useful source of raw material for the production of scaffolds for tissue engineering.

Electrochemical preparation and characterization of PNIPAM-HAp scaffolds for bone tissue engineering.

In the last decade, a variety of methods for fabrication of three-dimensional biomimetic scaffolds based on hydrogels have been developed for tissue engineering. However, many methods require the use of catalysts which compromises the biocompatibility of the scaffolds. The electrochemical polymerization (ECP) of acrylic monomers has received an increased attention in recent years due to its versatility in the production of highly biocompatible coatings for the electrodes used in medical devices. The main aim of this work was the use of ECP as scaffold fabrication technique to produce highly porous poly(N-isopropylacrylamide) (PNIPAM)/hydroxyapatite (HAp) composite for bone tissue regeneration. The prepared PNIPAM-HAp porous scaffolds were characterized by SEM, FTIR, water swelling, porosity measurements and X-ray diffraction (XRD) techniques. FTIR indicates that ECP promotes a successful conversion of NIPAM to PNIPAM. The water swelling and porosity were shown to be controlled by the HAp content in PNIPAM-HAp scaffolds. The PNIPAM-HAp scaffolds exhibited no cytotoxicity to MG63 cells, showing that ECP are potentially useful for the production of PNIPAM-HAp scaffolds. To address the osteomyelitis, a significant complication in orthopedic surgeries, PNIPAM-HAp scaffolds were loaded with the antibiotic oxacillin. The oxacillin release and the bacterial killing activity of the released oxacillin from PNIPAM-HAp against S. aureus and P. aeruginosa were demonstrated. These observations demonstrate that ECP are promising technique for the production of non-toxic, biocompatible PNIPAM-HAp scaffolds for tissue engineering.

Fabrication of electrospun HPGL scaffolds via glycidyl methacrylate cross-linker: Morphology, mechanical and biological properties.

Electrospinning is a suitable method to produce scaffolds composed of nanoscale to microscale fibers, which are comparable to the extracellular matrix (ECM). Hyperbranched polyglycerol (HPGL) is a highly biocompatible polyether polyol potentially useful for the design of fibrous scaffolds mimicking the ECM architecture. However, scaffolds developed from HPGL have poor mechanical properties and morphological stability in the aqueous environments required for tissue engineering applications. This work reports the production of stable electrospun HPGL scaffolds (EHPGLS) using glycidyl methacrylate (GMA) as cross-linker to enhance the water stability and mechanical property of electrospun HPGL. The diameter and morphology of the produced EHPGLS were analyzed by scanning electron microscopy (SEM). It was observed that electrical fields in the range of 0.2kV·cm-1 to 1.0kV·cm-1 decrease the average fiber diameter of EHPGLS. The increase in porosity of EHPGLS with GMA concentration indicates the in situ formation of a heterogeneous structure resultant from the phase separation during crosslinking of HPGL by GMA. EHPGLS containing 20% (w/w) GMA concentration possessed highest tensile strength (295.4±11.32kPa), which is approximately 58 times higher than that of non-crosslinked EHPGLS (5.1±2.12kPa). The MTS cell viability results showed that the EHPGLS have no significant cytotoxicity effect on Chinese hamster ovary (CHO-K1) cells. Scanning electron microscopy (SEM) indicates that the cultured BALB/3T3 fibroblasts cells were able to keep contact each other's, thus forming a homogeneous monolayer on the internal surface of the EHPGLS.

A novel drug delivery of 5-fluorouracil device based on TiO2/ZnS nanotubes.

The structural and electronic properties of titanium oxide nanotubes (TiO2) have attracted considerable attention for the development of therapeutic devices and imaging probes for nanomedicine. However, the fluorescence response of TiO2 has typically been within ultraviolet spectrum. In this study, the surface modification of TiO2 nanotubes with ZnS quantum dots was found to produce a red shift in the ultra violet emission band. The TiO2 nanotubes used in this work were obtained by sol-gel template synthesis. The ZnS quantum dots were deposited onto TiO2 nanotube surface by a micelle-template inducing reaction. The structure and morphology of the resulting hybrid TiO2/ZnS nanotubes were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. According to the results of fluorescence spectroscopy, pure TiO2 nanotubes exhibited a high emission at 380nm (3.26eV), whereas TiO2/ZnS exhibited an emission at 410nm (3.02eV). The TiO2/ZnS nanotubes demonstrated good bio-imaging ability on sycamore cultured plant cells. The biocompatibility against mammalian cells (Chinese Hamster Ovarian Cells-CHO) suggesting that TiO2/ZnS may also have suitable optical properties for use as biological markers in diagnostic medicine. The drug release characteristic of TiO2/ZnS nanotubes was explored using 5-fluorouracil (5-FU), an anticancer drug used in photodynamic therapy. The results show that the TiO2/ZnS nanotubes are a promising candidate for anticancer drug delivery systems.

Dendronized polyaniline nanotubes for cardiac tissue engineering.

Today, nanobiomaterials represent a very important class of biomaterials because they differ dramatically in their bulk precursors. The properties of these materials are determined by the size and morphology, thus creating a fascinating line in their physicochemical properties. Polyaniline nanotubes (PANINTs) are one of the most promising nanobiomaterials for cardiac tissue engineering applications due to their electroactive properties. The biocompatibility and low hydrophilic properties of PANINTs can be improved by their functionalization with the highly hydrophilic polyglycerol dendrimers (PGLDs). Hydrophilicity plays a fundamental role in tissue regeneration and fundamental forces that govern the process of cell adhesion and proliferation. In this work, the biocompatible properties and cardiomyocyte proliferation onto PANINTs modified by PGLD are described. PGLDs were immobilized onto PANINTs via surface-initiated anionic ring-opening polymerization of glycidol. The microstructure and morphology of PGLD-PANINTs was determined by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The cardiac cell growth on the PGLD-PANINTs was investigated. The PGLD-coated PANINTs showed noncytotoxic effects to Chinese hamster ovary cells. It was observed that the application of microcurrent stimulates the differentiation of cardiac cells cultured on PGLD-PANINTs scaffolds. The electroactive and biocompatible results of PGLD-PANINTs observed in this work demonstrate the potential of this nanobiomaterial for the culture of cardiac cells and open the possibility of using this material as a biocompatible electroactive three-dimensional matrix in cardiac tissue engineering.

A bioconjugated polyglycerol dendrimer with glucose sensing properties.

In this work, the biological and electrochemical properties of glucose biosensor based on polyglycerol dendrimer (PGLD) is presented. Streptokinase (SK), glucose oxidase (GOx) and phosphorylcholine (PC) were immobilized onto PGLD to obtain a blood compatible bioconjugate with glucose sensing properties. The bioconjugated PGLD was entrapped in polyaniline nanotubes (PANINT's) through template electrochemical polymerization of aniline. PANINT's were used as electron mediator due to their high ability to promote electron-transfer reactions involving GOx. Platelet adhesion, fibrinolytic activity and protein adsorption were studied by in vitro experiments to examine the interaction of blood with PGLD biosensor. The PGLD biosensor exhibits a strong and stable amperometric response to glucose. The enzyme affinity for the substrate (K (M) (app) ) indicates that the enzyme activity was not significantly altered after the bioconjugation of GOx with PGLD dendrimer. The bioelectrochemical properties suggest that the bioconjugated PGLD developed in this work appears to be a good candidate for providing interfaces for implantable biosensors, especially oxidoreductase-based sensors.

Antithrombogenic properties of bioconjugate streptokinase-polyglycerol dendrimers.

Dendrimers are monodisperse, spherical and hyperbranched synthetic macromolecules with a large number of surface groups that have the potential to act as carriers for drug immobilization by covalent binding or charge transfer complexation. In this work, a bioconjugate of streptokinase and a polyglycerol dendrimer (PGLD) generation 5 was used to obtain fibrinolytic surfaces. The PGLD dendrimer was synthesized by the ring opening polymerization of deprotonated glycidol using polyglycerol as core functionality in a step-growth processes denominated divergent synthesis. The PGLD dendritic structure was confirmed by gel permeation chromatography (GPC), nuclear magnetic resonance (1H-NMR, 13C-NMR) and matrix assisted laser desorption/ionization (MALDI-TOF) techniques. The synthesized dendrimer presented low dispersion in molecular weights (Mw/Mn = 1.05) and a degree of branching of 0.82 which characterize the polymer dendritic structure. The blood compatibility of the bioconjugate PGLD-Sk was evaluated by in vitro assays such as platelet adhesion and thrombus formation. Uncoated polystyrene -microtitre plates (ELISA) was used as reference. The epifluorescence microscopy results indicate that PGLD-Sk coating showed an improved antithrombogenic character relative to the uncoated ELISA plates.

Macroporous poly(epsilon-caprolactone) with antimicrobial activity obtained by iodine polymerization.

The most serious problem usually encountered in the field of implanted biomedical devices is infectious morbidity as a primary source of mortality. In this work, the synthesis and characterization of a macroporous iodine-based sanitizer (iodophor), poly(caprolactone)-iodine (PCL-I(2)), are presented. Characterization methods include nuclear magnetic resonance spectroscopy, gel permeation chromatography, nitrogen adsorption-desorption, and scanning electron microscopy. The in vitro cytotoxicity to CHO cells based on cell viability with Chinese hamster ovary cells (CHO) and antimicrobial activities against Escherichia coli and Staphylococcus aureus were examined. The obtained macropore PCL-I(2) structures had a rather narrow size distribution. The PCL-I(2) iodophor was noncytotoxic to Chinese hamster ovary cells. The antimicrobial activities of the PCL-I(2) were assessed against E. coli and S. aureus. The tested PCL-I(2) showed better antimicrobial activity against E. coli than against S. aureus.

Digital image processing for biocompatibility studies of clinical implant materials.

The use of computer vision coupled with scanning electron microscopy (SEM) was used to monitor the platelet adhesion and activation onto blood-contacting materials. The interaction of blood platelets with polyethylene (PE), poly(ethylene terephthalate) (PET), and poly(vinylchloride) (PVC) after contact of the polymeric surfaces with whole blood was studied. The SEM images (SEM Phillips XL 30) were captured using HLImage++ computer vision systems. A library with a considerable number of acceptance or rejection of samples has been conceived and implemented. The obtained results make the developed computational vision system a promising tool for the evaluation of blood compatibility of biomaterials.

Development of new hydroactive dressings based on chitosan membranes: characterization and in vivo behavior.

Different poly(vinyl alcohol) (PVA)/chitosan lactate (ChL)-blended hydrogels containing nitrofurazone as a local anti-infective drug were prepared by the phase-inversion technique. The swelling degree, surface free energy, mechanical properties, and nitrofurazone release of these membranes were determined. Blood compatibility of these systems was evaluated by the open-static platelet adhesion test with whole human blood. The results showed that water absorption into the PVA/ChL membranes slowed down, governed by the rate at which the dressing interacted with the physiological fluid. Swelling degree values up to 200% were observed. The rate of release of nitrofurazone seemed to depend on the ChL percentage on the blend as well as the pH of the solution. The surface free energy values were in the range of 20-30 dynes/cm, which was appropriate for a favorable interaction with blood. From the Young's module curve, it could be seen that elastic hydrogels were obtained with increment of ChL in the PVA/ChL blends. Values of platelet adhesion and whole blood clotting times for the PVA/ChL blends as well as the increase of ChL, which appears to reduce the fibrinogen adsorption on the PVA/ChL membranes, demonstrated that the blood compatibility of PVP/ChL blends is superior to that separated polymers. The results of in vivo experiments in rats were in very good agreement with these observations, suggesting that PVA/ChL may serve as a new type of potential wound-dressing material.