Biopolymers matrix

Hydrogel micro- and nanoparticles composed of biopolymer matrixes have gained a lot of attention in recent years due to their application in drug delivery and tissue engineering [10,14,45 17], The biopolymers used for these purposes are nontoxic,... 

As was pointed out above, the processing and in-use biopolymer properties depend on the addition of other materials that provide a more convenient processing regime and stabilizing effects. Therefore the identification and further determination of these additives, as well as the separation from the biopolymer matrix, is necessary, and chromatographic techniques are a powerful tool to achieve this goal. 

Fnrther research is needed to identify concomitantly the biopolymer matrix and the encapsulated active molecules by this nondestructive FTIR spectroscopy. 

As an extension to the considerable amount of research undertaken on processing and properties of natural filler composites, in this last decade, a number of researchers have explored the concept of namral filler-reinforced PLA composites. An outstanding one is the project FAlR-CT-98-3919 (New ftmctional biopolymer-natural fiber composites from agriculture resources) by European Union, in which one of the key objectives was to manufacture demonstration parts on a pre-competitive level with the automotive industry as the main potential market. Within this project, Lanzillotta et al. [21] prepared biocomposites with flax fibers and PLA as the biopolymer matrix. The research focused on the idea of converting biocomposites into products for real automotive applications. 

The described biopolymers are embedded in a biopolymer matrix whose task is to guarantee the stability of the structure, to protect the mechanically high-quality fibres from radiation and aggressive infiuences, and to transmit shear forces. The polymers are usually subdivided into thermosets and thermoplastics which are equally suitable as matrices for the structural material. 

CNCs within a biopolymer matrix to be prepared and provides a versatile approach for preparing new types of CNC-based hydrogels [93]. 

Bio-nanocomposites represent a stimulating route for creating new and innovative materials, where a large variety of superior properties have been realised and the opportunity to identify further advancements in the property behaviour is immense. These materials consist of a biopolymer matrix reinforced with particles having at least one dimension in the nanometer range i.e. 1-100 nm. Remarkable improvements have been reported for the mechanical, thermal and barrier properties of bio-nanocomposites in contrast to the base biopolymers [6]. This in turn makes this new class of materials very favourable for numerous end use apphcations. 

The use of nanocomposites for biomedical and clinical applications requires the selection of the appropriate biopolymer matrix, since it can have a profound impact on the quality of the newly formed tissue. Given that few biomaterials possess all the necessary characteristics for such application, researchers have pursued the development of hybrid or composite biomaterials to get synergies from the beneficial properties of multiple materials. The combination of biopolymers with nanostructured materials, including the use of nanoparticles, nanofibres and other nanoscaled features, has demonstrated the ability to enhance cellular interaction, to encourage integration into host tissue and to provide tunable material properties and degradation kinetics. Materials with nanometre scaled dimensions, also known as nanophase or nanostructured materials, can be used to produce nanometre features on the surface of three-dimensional substrates for scaffolds. 

It is now well identified that bacteria connect to solid supports to shape structured communities called biofilms, also known as biopolymer matrix-enclosed microbial populations adhering to each other and/or surfaces [111]. Biofihns occur on both living and inert supports in all environments [112]. They influence various industrial and domestic areas [113] and are accountable for a broad range of human diseases [111], In view of the ever growing number of implanted patients, biofilm-linked infections of indwelling medical devices are more predominantly a foremost public health issue. Various examples of implants that can be inflated by biofilm formation are mechanical heart valves, catheters, pacemakers/defibriUators, ventricular assist devices, vascular prostheses, coronary stents, neurosurgical ventricular shunts, cerebrospinal fluid shunts, neurological stimulation implants, ocular prostheses, inflatable penile, cochlear, joint prostheses, fracture-fixation devices, breast, and dental implants and contact lenses, intrauterine contraceptive devices [114-116]. 

Biocomposites are obtained by the incorporation of macro-fillers (mainly ligno-cellulose fibres) in a biopolymer matrix. One of the main advantages of... 

FIGURE 4.1 Schematic approach used in the modification of biopolymers (a) blends, (b) chemical linkages, (c) cross-linking, (d) grafting, and (e) biocomposite formation (i, biopolymer matrix ii, biopolymer fillers iii, surface modified inorganic materials). (See insert for color representation of the figure.)... 

Among the entire potential nanocomposite precursors, those based on layered silicates have been most widely researched probably because the starting clay materials are easily available and environmentally friendly, due to their low cost, and because their intercalation chemistry has been studied for a long time [25], Biopolymer-clay nanocomposites are a new type of materials, which are prepared by adding low amounts of clay (1-5%) to the biopolymer matrix [26]. Montmorillonite is the most commonly used natural clay and has been successfully applied in numerous nanocomposite systems [13], Some studies have reported amelioration of mechanical properties, thermal stability, water absorption, and electrical, rheological, and morphological properties of alginate films via the incorporation of nanoclay into polymer matrices [27],... 

The functional biopolymer matrix in biominerals is a multicomponent mixture with the possibility of all kinds of interactions and this makes the analysis of the individual polymer components difficult. Also, the biomineralization proteins are often polydisperse, have a non-globular shape and multiple charges and post translational modifications, which further hampers the protein separation. It is even more difficult to reveal their function as they are not only present in a polymer mixture with the associated possibUity of polymer interactions, but are furthermore often only active for a certain time. For example, in calcified parts of crustacean cuticles, 33 different proteins have already been identified [ 153] so that it is difficult to reveal the fimctions of individual biomineralization polymers. 

Tensile properties are, by far, the most widely studied mechanical properties of eco-friendly polymer nanocomposites. Overall, the mechanical performance of CNC-reinforced composites depends on the aspect ratio, crystallinity, processing method, and CNC/matrix interfacial interaction. The mechanical properties are proportional to aspect ratio and crystaUinify of nanoreinforcement and it has been shown that increase in aspect ratio and crystaUinify results in increase in mechanical properties. Slow processing methods which encourage water evaporation result in composites with improved properties. This is because nanoparticles have suflticient time to interact and connect to form a continuous network, which is the basis of their reinforcing effect. Nanoreinforcement which is compatible with the biopolymer matrix also exhibits improved mechanical properties of the nanocomposites. 

It has been shown that if cellulose nanoreinforcement can be made to align in a biopolymer matrix, they exhibit optimum properties in the direction of alignment, just like in synthetic fiber composites. Chitosan is a semicrystalline biopolymer which is used both as a matrix and as nanoreinforcement in composites. The use of chitosan nanoreinforcements in biopolymer matrices results in improvement in properties of composites. However, an optimum loading limit has been observed, depending on the biopolymer matrix, above which the properties of nanocomposites start to decline. A similar optimum loading limit has been found to exist when CNCs are used as reinforcements in chitosan matrix. 

Bio-nanocomposite film showed improved barrier properties by dispersing NPs in the biopolymer matrix, which in turn provide a tortuous path for gas molecules to pass througLThe Figure 4 clearly depicts the difference between the gas permeability in pure viigin polymer films and through incorporated nanocomposite polymer matrix. In the case of nanocomposite polymer matrix (Figure 3(b)), gas molecules diffuse... 

The XRD patterns for various possible arrangements of layered silicates in biopolymers are shown in Figure 1. For an itmniscible arrangement (microcomposite) of layered clays in a biopolymer matrix, the structure of the layered silicate in the composite is not affected. Thus, XRD pattern for the microcomposite should remain same as that obtained for the pure layered silicate. Intercalation of the polymer... 

These future developments will help in better imderstanding of the interaction between nanoparticles and biopolymer matrix. This will aid in the synthesis of bionanocomposites with improved properties. 

Woerly S, Marchand R, Lavallee C. Intracerebral implantation of synthetic polymer/biopolymer matrix A new perspective for brain repair. Biomaterials 1990 11 97-107. 

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