Bioactive films

Bioactive films made by the LbL technique have been extensively studied by many scientific groups worldwide. The films can host not only bioactive molecules introduced as constituents of the film, but also carriers with encapsulated biomolecules, for instance liposomes (Lip) and polymeric capsules (Fig. 2). Stimuli-sensitive... 

Adsorption and release of dyes in PEMs is a perspective direction for development of new bioactive films with prolonged action. By varying PEMs structure, conditions of their formation, thickness, and also using various polyelectrolytes, it is possible to achieve the high dye loading and proper control of its release. 

Bioactive films of apatite can be prepared by sol- 1 method [25], and deposited on biomedical metallic implants, enhancing their bio-activity and so, reducing the... 

Tripathi, S., Mehrotra, G. K., Tripathi, C. K. M. et al., 2008a. Chitosan based bioactive film Functional properties towards biotechnological needs. Aiwn Chitin Journal, 4 29-36. 

Lobo, A. O., Otubo, J., Matsushima, J. T. and Corat, E. J. (2011), Rapid obtaining of nanohydroxyapatite bioactive films on NiTi shape memory alloy by electrodeposition process . Journal of Materials Engineering and Performance, 20,793-7. 

The next two examples illustrate more complex surface reaction chemistry that brings about the covalent immobilization of bioactive species such as enzymes and catecholamines. Poly [bis (phenoxy)-phosphazene] (compound 1 ) can be used to coat particles of porous alumina with a high-surface-area film of the polymer (23). A scanning electron micrograph of the surface of a coated particle is shown in Fig. 3. The polymer surface is then nitrated and the arylnitro groups reduced to arylamino units. These then provided reactive sites for the immobilization of enzymes, as shown in Scheme III. 

Recently, a novel method of Hb immobilization was achieved by Lu [120], The direct electrochemistry of Hb was successfully achieved by adsorbed Hb onto the surface of a yeast cell through electrostatic attractions on a GC electrode. The bioactivity of Hb immobilized in yeast cell film was retained, and the catalytic reduction of NO and H202 was estimated. 

Glass-cloth-reinforced laminates, silane performance in, 22 702 Glass coatings, thin-film, 12 608—609 Glass components, 12 595t Glass compositions, 12 594t 13 387 bioactive, 12 611... 

The higher surface area of CNTs can support a much higher density of enzymes than previous approaches such as thin films. Their high aspect ratio aids in the retention of enzyme-CNT conjugates in the matrix. CNTs also enhance the stability of adsorbed proteins relative to micro- or macro-scale supports, thereby helping to preserve or enhance enzyme bioactivity in the nanocomposites (Wang,... 

In this chapter an attempt has been made to discuss ordered structures made using the LB technique and employing relatively simple molecules all of one kind. In the next chapter, films made from preformed polymers, from polymerisable small molecules and from alternating layers of two distinct kinds of molecule will be discussed. Once again the emphasis will be on structure and the characterisation of order. The discussion of lipids and lipid-like materials is deferred until Chapter 8 which will discuss biomembranes and bioactive molecules. At this stage the reader may well ask What of the vast number of other simple materials from which LB films have been made ... 

As an extension of the HA film approach, Yun and coworkers [32] synthesized hyaluronan microspheres using the chemistry described above, but the synthesis was completed in emulsion in one step, yielding 5- to 20-pm microspheres. These microspheres were found to be biodegradable and released three times more pDNA when incubated with hyaluronidase in PBS (phosphate buffered saline) solution (vs enzyme-free PBS). As in the case of films, DNA release from the microspheres was dependent on the DNA loading. DNA-HA microspheres were not directly used for transfection instead, DNA obtained from release experiments was used in transfection of Chinese hamster ovary (CHO) cells using Lipofectamine. The relative levels of transfection over time had the same trend as DNA release from the DNA-HA microspheres and confirmed that released DNA is bioactive. 

Keywords Bioactive Layer-by-layer Multilayered films Polyelectrolyte self-assembly Remote release... 

Bioactive macromolecules like peptides, proteins, and nucleic acids have been successfully embedded in planar LbL films. An important question is the retention of the bioactivity of the film-embedded biomolecules. The structural properties and stability of the LbL films formed from synthesized polypeptides of various amino acid sequences were recently reported [50]. The authors showed that control over the amino acid sequence enables control over non-covalent interpolypeptide interaction in the film, which determines the film properties. Haynie and coworkers showed by circular dichroism spectroscopy that the extent of adsorption of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) in the LbL films scales with the extent of secondary structure of the polypeptides in solution [51]. Boulmedais demonstrated that the secondary structure of the film composed of these polypeptides is the same as the peptide structure in the complex formed in solution [52], as found by Fourier transform IR spectroscopy (FUR). 

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