Multiple compartment technique

Figure 6.21 Pressurized apparatus, Group I, multiple compartment technique [31],...

Because optical trapping does not require physical contact, cells can be manipulated in a completely enclosed environment in which physical and chemical parameters can be maintained over time. Specially designed chambers have been used that contain multiple compartments into which cells can be sorted automatically on the basis of optical characteristics not recognizable by conventional flow-sorting techniques (26,27). 

FTIR instrumentation is mature. A typical routine mid-IR spectrometer has KBr optics, best resolution of around 1cm-1, and a room temperature DTGS detector. Noise levels below 0.1 % T peak-to-peak can be achieved in a few seconds. The sample compartment will accommodate a variety of sampling accessories such as those for ATR (attenuated total reflection) and diffuse reflection. At present, IR spectra can be obtained with fast and very fast FTIR interferometers with microscopes, in reflection and microreflection, in diffusion, at very low or very high temperatures, in dilute solutions, etc. Hyphenated IR techniques such as PyFTIR, TG-FTIR, GC-FTIR, HPLC-FTIR and SEC-FTIR (Chapter 7) can simplify many problems and streamline the selection process by doing multiple analyses with one sampling. Solvent absorbance limits flow-through IR spectroscopy cells so as to make them impractical for polymer analysis. Advanced FTIR... 

Electrical and optical connections between two flameproof enclosures separated by a partition wall are made by the insertion of (multiple) cable bushings or fibre bushings in an opening or thread of the partition wall. This technique is identical with the means of connection between e - and d -compartments (see Section 6.7.2, Table 6.19, and Section 6.7.6, Fig. 6.70, and, in addition, Fig. 6.84). 

However, in the light of multiple experimental findings based upon more accurate and precise techniques, this model seems to be oversimplified since it does not take into account the potential transfer of drugs from sweat, sebaceous and apocrine gland secretions, nor the external contamination even via deep compartments located in the skin surrounding the hair follicle. 

Centrifugation is a powerful technique allowing the parallel processing of an unlimited number of reaction compartments (101). The first centrifugal multiple peptide synthesizer, Compas 242 (76,102), utilized centrifugation for liquid removal from the functionalized cotton used as the solid support or from resin contained in polypropylene mesh bags (703). This system enabled the automation of tea-bag synthetic methodology. In principle, however, separation of solid and liquid phases was still accomplished by filtration. 

The term encapsulation has been used to distinguish entrapment preparations in which the biocatalyst environment is comparable to that of the bulk phase and where there is no covalent attachment of the protein to the containment medium (Fig. 6-1 D)[21J. Enzymes or whole cells may be encapsulated within the interior of a microscopic semi-permeable membranes (microencapsulation) or within the interior of macroscopic hollow-fiber membranes. Liposome encapsulation, a common microscopic encapsulation technique, involves the containment of an enzyme within the interior of a spherical surfactant bilayer, usually based on a phospholipid such as lecithin. The dimensions and shape of the liposome are variable and may consist of multiple amphiphile layers. Processes in which microscopic compart-mentalization (cf. living cells) such as multienzyme systems, charge transfer systems, or processes that require a gradient in concentration have employed liposome encapsulation. This method of immobilization is also commonly used for the delivery of therapeutic proteins. 

This is another innovative emulsion technique proposed for the efficient encapsulation of hydrophilic drug compounds involves the formation of double emulsions (multiple emulsions). In this technique, an aqueous core solution (W,) is emulsified in a polymer-organic solvent solution (O) to form the primary W/0 emulsion, which is further emulsified in an external aqueous solution (Wn), giving rise to the double emulsion of Wi/O/Wu type. Evaporation or extraction of the organic solvent yields a solid microcapsule with an aqueous core. The organic phase in (O) acts as a barrier between the two aqueous compartments, W, and Wu, to prevent the diffusion of hydrophilic drug compounds out of the core toward the external aqueous solution. Figure 45.5 depicts the microencapsulation by the Wi/O/Wn emulsion technique. 

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