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 (K_m) and 0.49 U/mg (V_max) 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.

Interactions of polyglycerol dendrimers with human serum albumin: insights from fluorescence spectroscopy and computational modeling analysis

Polyglycerol dendrimer synthesized from glycerol core (PGLyD) is an interesting reservoir macromolecule for the design of drug delivery systems due to their adequate blood biocompatibility. However, important features as the comprehension of the structural and dynamic characteristics and the interactions of PGLyD with blood proteins receptors remain unresolved. The high affinity and transport of HSA with drugs stimulated the docking simulations utilizing PGLyD as a ligand for the main HSA docking sites IIA and IIIA. HSA and the PGLyD structures were generated with the aid of Autodock Vina and the best conformations were determined by employing molecular docking. The molecular docking results indicate a thermodynamically favorable interaction suggesting a charge transfer complex formation between HSA and PGLyD. The interaction between PGLyD and HSA was investigated by fluorescence and the quenching mechanism of fluorescence of HSA by PGLyD was discussed. The binding constants and the number of binding sites were measured. The values of thermodynamic parameters ΔG, ΔH, and ΔS were calculated at three different temperatures. The experimental and computational results suggest that hydrophobic forces play a major role in stabilizing the HSA-PGLyD complex.

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.

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.

Neural Networks for an Analysis of the Hemometabolites Biosensor Response

In this work, the concentration dependent response of amperometric biosensor array for the biomarkers glucose, cholesterol and urease was explored, using artificial neural nets (ANN). The aim was to explore an array of amperometric biosensors for the discrimination of the biomarkers glucose, cholesterol and urea in blood. Seven out of eight platinum electrodes on the array were modified with four different enzymes; glucose oxidase, cholesterol, urease and peroxidase. The dynamic biosensor response curves from the eight sensors were used for ANN analysis. The ANN were applied to an analysis of the biosensor response to multi-biomarkers mixtures the ANN was able to detect the conditions with an accuracy up to 90%. The results obtained by using ANN to interpret the electrical signal of the developed biosensor arrays leads to the conclusion that: i) after training the ANN, the evaluation of recorded data are on-line, ii) microelectrode sites which are highly correlated to the information about the concentrations within the recorded signals was identified, iii) the recognition of blood biomarkers is improved by using the ANN.

Physicochemical and antimicrobial properties of boron-complexed polyglycerol–chitosan dendrimers

A polyglycerol with dendritic structure (PGLD) was synthesized by ring-opening polymerization of deprotonated glycidol using a polyglycerol as core functionality in a step-growth process. Then, PGLD reacted with O-carboxymethylated chitosan to obtain PGLD-chitosan dendrimer (PGLD-Ch). After the reaction of PGLD-Ch with boric acid, there was a marked increase in the bulk viscosity evidencing physically that boron can initiate a charge transfer complex formation, (PGLD-Ch)B. Gel permeation chromatography analysis was used to characterize the molecular weight and the polydispersivity of the synthesized PGLD-Ch. A dendritic structure with a molecular mass of 16.7 kDa and a narrow polydispersity (Mw/Mn = 1.05) was obtained. 1H-NMR and 13C-NMR measurements were employed to assess the degree of branching in PGLD. The obtained value of 0.85 indicates the tendency toward a dentritic structure for PGLD. The glass transition temperature values of (PGLD-Ch)B membranes containing 10% and 30% PGLD were -19 degrees C and -26 degrees C, respectively, which favor its potential use as surface coating of several polymers. The in vitro cytotoxicity was evaluated using the minimum essential medium elution test assay. Extracts of boron-complexed PGLD exhibited lower cytotoxicity than the controls, suggesting that the material has an improved biocompatibility. Antibacterial studies of (PGLD-Ch)B against Staphylococcus aureus and Pseudomonas aeruginosa showed a significant activity. Our study confirms and supports the effectiveness of (PGLD-Ch)B as an antimicrobial coating due to its capacity in suppressing the bacterial proliferation. The best in vivo response was found for (PGLD-Ch)B-30 membranes, which exhibited higher synthesis of collagen fibers than PGLD-ChB-10.

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(ϵ-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.