Surface biological tissues

Poly(ethylene oxide)—Poly(ethylene terephthalate) Copolymers. The poly(ethylene oxide)-poly(ethylene terephthalate) (PEO/PET) copolymers were first described in 1954 (40). This group of polymers was developed in an attempt to simultaneously reduce the crystallinity of PET, and increase its hydrophilicity to improve dyeabiHty. PEO/PET copolymers with increased PEO contents produce surfaces that approach zero interfacial energy between the implant and the adjacent biological tissue. The coUagenous capsule formed around the implant is thinner as the PEO contents increase. The stmcture of a PEO/PET copolymer is shown below ... 

There are many obstacles to permanent adhesion under oral conditions. The substrate is a biological tissue and subject to change, and the presence of moisture represents the worst kind of situation for adhesion. Water is the great barrier to adhesion. It competes for the polar surface of tooth material against any potential polymer adhesive. It also tends to hydrolyse any adhesive bond formed. These twin obstacles gave rise to considerable doubt as to whether materials adhesive to tooth material could be developed at all (Cornell, 1961). 

Because MALDI is a desorption technique, it is particularly suited for the analysis of surfaces such as biological tissues [50]. In this application, the matrix is applied on the complete surface of the tissue. The laser resolution is about 100 pm and complete analyte distribution images (low molecular weight compounds, peptides, proteins) can be recorded [51, 52]. 

An additional benefit of SORS is the suppression of surface-generated fluorescence which has an identical spatial (but not temporal) distribution to the Raman signal of the surface layer. This feature is particularly beneficial in situations where intense surface-layer fluorescence masks the underlying Raman signal examples include melanin-induced fluorescence in biological tissue in vivo and intensely coloured capsules or coated tablets in pharmaceutical applications. 

Bioadhesive formulations and microsphere delivery systems in particular have attracted much attention. As drug formulations are usually rapidly removed from the site of deposition by the mucociliary clearance, increasing the retention time of drug in the nasal cavity via bioadhesion can increase bioavailability [28], Bioadhesion may be defined as the ability of a material (synthetic or biological) to adhere to a biological tissue for an extended period of time. When applied to a mucous membrane, a bioadhesive polymer may adhere primarily to the mucus layer or epithelial cell surface in a phenomenon known as mucoadhesion [29,30]. The bioadhesive properties of a wide range of materials have been evaluated over the last decade. 

The sample preparation plays a very important role for the analysis of a drug and its metabolites in biological tissue sections using mass spectrometric imaging. Several factors in IMS sample preparation must be considered, from sample collection to surface treatment prior to analysis in order to produce high quality, reliable, and reproducible results. 

Mucoadhesive Polymers Bioadhesion refers to the attachment of a drug molecule or a delivery system to a specific biological tissue by means of interfacial forces. If the surface of the tissue is covered by a mucin film, as is the case for the external globe, it is more commonly referred to as mucoadhesion. 

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