Biopharmaceutical proteins absorbance

More recently, increasing research attention has focused upon the use of mucoadhe-sive delivery systems in which the biopharmaceutical is formulated with/encapsulated in molecules that interact with the intestinal mucosa membranes. The strategy is obviously to retain the drug at the absorbing surface for a prolonged period. Non-specific (charge-based) interactions can be achieved by the use of polyacrylic acid, whereas more biospecihc interactions are achieved by using selected lectins or bacterial adhesion proteins. Despite intensive efforts, however, the successful delivery of biopharmaceuticals via the oral route remains some way off. 

Fortunately, protein concentration methods are relatively simple (low-tech) and inexpensive. The simplest assays require only a spectrophotometer calibrated for wavelength and absorbance accuracy, basic laboratory supplies, and good pipetting techniques. Protein concentration assays are quite sensitive, especially given the typical detection limits required for most biopharmaceuticals. 

Because of the sensitive nature of most biopharmaceuticals, their dosage forms are limited to injectable solutions. Therapeutic proteins cannot pass the acidic milieu of the stomach undamaged, nor are they absorbed through the intestinal wall. Although work on alternatives such as inhalers is underway (the first commercial application is an insulin inhaler), injection remains the predominant option for administering sensible biopharmaceuticals. 

Applications in Biotechnology. Biopharmaceutical products must be well characterized by means of analytical techniques. RP-HPLC with UV detection is suitable for the content assay and impurity profiling because of its high resolution. However, the bioactivity of protein-based pharmaceuticals not only relies on the primary structure but also on the higher order structure, i.e., the molecular confirmation, which is not revealed by UV absorbance. Circular dichroism and intrinsic fluorescence detection have been combined with UV detection in RP-HPLC to monitor the conformational properties of active compounds and impurities in biopharmaceutical products [57]. 

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