Surface Functionalities of Polymers for Biomaterial Applications.

Changes of a material biointerface allow for specialized cell signaling and diverse biological responses. Biomaterials incorporating immobilized bioactive ligands have been widely introduced and used for tissue engineering and regenerative medicine applications in order to develop biomaterials with improved functionality. Furthermore, a variety of physical and chemical techniques have been utilized to improve biomaterial functionality, particularly at the material interface. At the interface level, the interactions between materials and cells are described. The importance of surface features in cell function is then examined, with new strategies for surface modification being highlighted in detail.

Characterisation of Hemp Fibres Reinforced Composites Using Thermoplastic Polymers as Matrices.

Hemp fibres used as a reinforcing agent and three polymeric matrices (polypropylene, bicomponent, recycled polyester) were used to obtain composite materials by needle punching and heat pressing. The influence of the hemp/matrix ratio and the nature of the matrix on the properties of the composites were analysed. The obtained composites were characterised by physical-mechanical indices, thermal analysis (thermogravimetry (TG), differential thermogravimetry (DTG) and Differential Scanning Calorimetry (DSC)), Fourier Transform Infrared Spectroscopy (FTIR-ATR) analysis, Scanning Electron Microscopy (SEM) and Chromatic measurements. The mechanical properties of composites are influenced by both the hemp/matrix ratio and the nature of the matrix. The thermal stability of composites decreased as the amount of hemp increased (for the same mass losses, the decomposition temperature decreased significantly for composites containing a quantity of hemp greater than 50%). Regarding the nature of the matrix, for the same mass loss, the highest decomposition temperature was presented by the composites containing recycled polyester as matrix, and the lowest one was presented by composites containing polypropylene fibres as matrix. The FTIR and SEM analyses highlight the changes that occurred in the structure of the composite, changes determined both by the amount of hemp in the composite and by the nature of the matrix.

Composite Materials Based on Gelatin and Iron Oxide Nanoparticles for MRI Accuracy.

The majority of recent studies have focused on obtaining MRI materials for internal use. However, this study focuses on a straightforward method for preparing gelatin-based materials with iron oxide nanoparticles (G-Fe2O3 and G-Fe3O4) for external use. The newly obtained materials must be precisely tuned to match the requirements and usage situation because they will be in close touch with human/animal skin. The biocompatible structures formed by gelatin, tannic acid, and iron oxide nanoparticles were investigated by using FTIR spectroscopy, SEM-EDAX analysis, and contact angle methods. The physico-chemical properties were obtained by using mechanical investigations, dynamic vapor sorption analysis, and bulk magnetic determination. The size and shape of iron oxide nanoparticles dictates the magnetic behavior of the gelatin-based samples. The magnetization curves revealed a typical S-shaped superparamagnetic behavior which is evidence of improved MRI image accuracy. In addition, the MTT assay was used to demonstrate the non-toxicity of the samples, and the antibacterial test confirmed satisfactory findings for all G-based materials.

Tunable Properties via Composition Modulations of Poly(vinyl alcohol)/Xanthan Gum/Oxalic Acid Hydrogels.

The design of hydrogel networks with tuned properties is essential for new innovative biomedical materials. Herein, poly(vinyl alcohol) and xanthan gum were used to develop hydrogels by the freeze/thaw cycles method in the presence of oxalic acid as a crosslinker. The structure and morphology of the obtained hydrogels were investigated by means of scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and swelling behavior. The SEM analysis revealed that the surface morphology was mostly affected by the blending ratio between the two components, namely, poly(vinyl alcohol) and xanthan gum. From the swelling study, it was observed that the presence of oxalic acid influenced the hydrophilicity of blends. The hydrogels based on poly(vinyl alcohol) without xanthan gum led to structures with a smaller pore diameter, a lower swelling degree in pH 7.4 buffer solution, and a higher elastic modulus. The antimicrobial activity of the prepared hydrogels was tested and the results showed that the hydrogels conferred antibacterial activity against Gram positive bacteria (Staphylococcus aureus 25923 ATCC) and Gram negative bacteria (Escherichia coli 25922 ATCC).

Comparative Investigation of Collagen-Based Hybrid 3D Structures for Potential Biomedical Applications.

Collagen is a key component for devices envisaging biomedical applications; however, current increasing requirements impose the use of multicomponent materials. Here, a series of hybrid collagen-based 3D materials, comprising also poly(ε-caprolactone) (PCL) and different concentrations of hyaluronic acid (HA)-in dense, porous or macroporous form-were characterized in comparison with a commercially available collagen sponge, used as control. Properties, such as water uptake ability, water vapour sorption, drug loading and delivery, were investigated in correlation with the material structural characteristics (composition and morphology). Methylene blue (MB) and curcumin (CU) were used as model drugs. For spongeous matrices, it was evidenced that, in contrast to the control sample, the multicomponent materials favor improved sustained release, the kinetics being controlled by composition and cross-linking degree. The other characteristics were within an acceptable range for the intended purpose of use. The obtained results demonstrate that such materials are promising for future biomedical applications (wound dressings and lab models).

Composite Materials Based on Iron Oxide Nanoparticles and Polyurethane for Improving the Quality of MRI.

Polyether urethane (PU)-based magnetic composite materials, containing different types and concentrations of iron oxide nanostructures (Fe2O3 and Fe3O4), were prepared and investigated as a novel composite platform that could be explored in different applications, especially for the improvement of the image quality of MRI investigations. Firstly, the PU structure was synthetized by means of a polyaddition reaction and then hematite (Fe2O3) and magnetite (Fe3O4) nanoparticles were added to the PU matrices to prepare magnetic nanocomposites. The type and amount of iron oxide nanoparticles influenced its structural, morphological, mechanical, dielectric, and magnetic properties. Thus, the morphology and wettability of the PU nanocomposites surfaces presented different behaviours depending on the amount of the iron oxide nanoparticles embedded in the matrices. Mechanical, dielectric, and magnetic properties were enhanced in the composites' samples when compared with pristine PU matrix. In addition, the investigation of in vitro cytocompatibility of prepared PU nanocomposites showed that these samples are good candidates for biomedical applications, with cell viability levels in the range of 80-90%. Considering all the investigations, we can conclude that the addition of magnetic particles introduced additional properties to the composite, which could significantly expand the functionality of the materials developed in this work.

Preparation and Characterization of Electrospun Collagen Based Composites for Biomedical Applications.

Electrospinning is a widely used technology for obtaining nanofibers from synthetic and natural polymers. In this study, electrospun mats from collagen (C), polyethylene terephthalate (PET) and a blend of the two (C-PET) were prepared and stabilized through a cross-linking process. The aim of this research was to prepare and characterize the nanofiber structure by Fourier-transform infrared with attenuated total reflectance spectroscopy (FTIR-ATR) in close correlation with dynamic vapor sorption (DVS). The studies indicated that C-PET nanofibrous mats shows improved mechanical properties compared to collagen samples. A correlation between morphological, structural and cytotoxic proprieties of the studied samples were emphasized and the results suggest that the prepared nanofiber mats could be a promising candidate for tissue-engineering applications, especially dermal applications.

Preparation and Evaluation of Nanofibrous Hydroxypropyl Cellulose and ß-Cyclodextrin Polyurethane Composite Mats.

A series of nanofibrous composite mats based on polyurethane urea siloxane (PUUS), hydroxypropyl cellulose (HPC) and ß-cyclodextrin (ß-CD) was prepared using electrospinning technique. PUUS was synthesized by two steps solution polymerization procedure from polytetramethylene ether glycol (PTMEG), dimethylol propionic acid (DMPA), 4,4'-diphenylmethane diisocyanate (MDI) and 1,3-bis-(3-aminopropyl) tetramethyldisiloxane (BATD) as chain extender. Then, the composites were prepared by blending PUUS with HPC or ßCD in a ratio of 9:1 (w/w), in 15% dimethylformamide (DMF). The PUUS and PUUS based composite solutions were used for preparation of nanofibrous mats. In order to identify the potential applications, different techniques were used to evaluate the chemical structure (Fourier transform infrared-attenuated total reflectance spectroscopy-FTIR-ATR), morphological structure (Scanning electron microscopy-SEM and Atomic force microscopy-AFM), surface properties (contact angle, dynamic vapors sorption-DVS), mechanical characteristics (tensile tests), thermal (differential scanning calorimetry-DSC) and some preliminary tests for biocompatibility and microbial adhesion.

Biopolymers/poly(ε-caprolactone)/polyethylenimine functionalized nano-hydroxyapatite hybrid cryogel: Synthesis, characterization and application in gene delivery.

Nano-hydroxyapatite (nHAp), surface functionalized with linear polyethylenimine (LPEI), was used for the preparation of biocomposites in combination with biopolymers and poly(ε-caprolactone) (PCL), by cryogelation technique, to yield biomimetic scaffolds with controlled interconnected macroporosity, mechanical stability, and predictable degradation behavior. The structural characteristics, swelling and degradation behavior of hydroxyapatite and hydroxyapatite/ß-tricalcium phosphate (ß-TCP) filled matrices were investigated as compared to the corresponding naked polymer 3D system. It was found that the homogeneity and cohesivity of the composite are significantly dependent on the size and amount of the included inorganic particles, which are thus determining the structural parameters. Surface modification with LPEI and nanodimensions favored the nHAp integration in the organic matrix, with preferential location along protein fibers, while ß-TCP microparticles induced an increased disorder in the hybrid system. The biocomposite including nHAp only was further investigated targeting biomedical uses, and proved to be non-cytotoxic and capable of acting as gene-activated matrix (GAM). It allowed sustained delivery over time (until 22days) of embedded PEI25-pDNA polyplexes at high levels of transgene expression, while insuring a decrease in cytotoxicity as compared to polyplexes alone. Experimental data recommend such biocomposite as an attractive material for regenerative medicine.

Comparison study of TEMPO and phthalimide-N-oxyl (PINO) radicals on oxidation efficiency toward cellulose.

Regenerated cellulose fibers, type viscose, have been oxidized with sodium hypochlorite and catalytic amounts of sodium bromide by using two different protocols: first, involving the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and second, employing N-hydroxyphthalimide (NHPI). The reactions were carried out at room temperature and pH=10.5 for 2.5h. Viscose oxidized samples were analyzed and compared in terms of the negative charged groups content, as determined by potentiometric titration and methylene blue adsorption, morphologies and crystallinities changes, as well as changes in the degree of polymerization. The highest content of the carboxylic groups and the best preservation of the morphology and molecular weight of the original material have been found in the case of using NHPI/anthraquinone as oxidation mediators. TEMPO-mediated oxidation leads to the highest depolymerization and cause significant degradation of the cellulosic material.