Protein-based materials control

J. C.M. van Hest, D.A. Tirrell, Protein-based materials, tow/ard a new level of structural control, Chem. Common. 19 (2001) 1897-1904. 

Proteins or amino acids are the major constituents present in natural tissues and they are well known for their controlled natural degradation ability. Such protein-based materials are especially useful in suturing applications, for scaffold... 

The Comprehensive Capacity to Control Association of Oil-like Domains Provides the Necessary Understanding for Meaningful Engineering of Protein-based Materials for Diverse Medical and Nonmedical Applications... 

Desirable at this point would be an implantable naltrexone delivery system that would not depend on patient compliance. It could be a biodegradable controlled release device, for example, injectable by hypodermic syringe for relatively short-term release. Alternatively, it could be implanted by trocar or by laparoscope for release for months as a biocompatible and biodegradable yet removable vehicle should patients circumstances warrant substantial pain control. As demonstrated below (see Figure 9.39), properly designed protein-based materials exhibit this potential. 

Protein-based polymers have the potential to surpass the polyesters and other polymers because they can be directly produced in microorganisms and plants by recombinant DNA technology resulting in the capacity for diverse and precisely controlled composition and sequence. This is not possible with any other polymer, and it increases range of properties and the numbers of applications. Remarkably, with the proper design of composition, protein-based materials can be thermoplastics, melting at temperatures as much as 100°C below their decomposition temperatures. Therefore, they can be molded, extruded, or drawn into shapes as desired. Aspects of protein-based materials as plastics is also considered below. 

Figure 9.24. Control for the prevention of adhesions following abdominal wounds. In the absence of a sheet of elastic protein-based material, major adhe-...

The special energy conversion (transductional) capacities designable into elastic protein-based materials provide unique opportunities for a remarkable range of systems capable of controlled delivery of drugs and other more complex therapeutic molecular constructs. Each of the 18 pairwise energy conversions,... 

ProLastin polymers are a family of protein-based materials w hose resorption rate in vivo can be controlled by adjusting the sequence and not just the composition of the polymer (Cappello et al, 1995). These adjustments can be made so as to cause little change in the formulation characteristics of the materials, their physical forms, or their mechanical properties. They have good mechanical integrity with no need for chemical crosslinking. They degrade by enzymatic proteolysis and are presumed to resorb by surface erosion. Their breakdowm products are peptides or amino acids w hich are electroneutral at physiological pH and cause no undue inflammation or tissue response. 

It is essential to determine the phase equilibrium patterns (Figure 1) of protein-based materials according to the moisture (or plasticizer) contents in order to be able to control the material formation conditions and predict variations in the properties of the end products under different usage conditions (temperature and relative humidity) 6,10,19JO),... 

Molecular imprinting is not limited to organic polymer matrices, but can also be applied to silica-based materials and even proteins. Proteins freeze-dried in the presence of a transition state analogue as template have been used successfully as catalysts, e.g., for the dehydrofluorination of a fluorobutanone. For instance, lyophilized 3-lactoglobulin imprinted in this manner with N-isopropyl-N-ni-trobenzyl-amine could accelerate the dehydrofluorination by a factor of 3.27 compared to the non-imprinted protein see Table 5 [62]. In a similar procedure, BSA was imprinted with N-methyl-N-(4-nitrobenzyl)-S-aminovaleric acid and showed an enhancement of the catalytic effect by a factor of 3.3 compared to the control protein for the same reaction see Table 5 [113]. 

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