One of the present challenges in polymer scaffold processing is the fabrication of three-dimensional (3D) architectures with an adequate mechanical performance to be used in the tissue engineering of hard tissues. This paper describes a preliminary study on the development of a new method to produce biodegradable scaffolds from a range of corn-starch-based polymers. In some cases, hydroxlapatite was also used as a reinforcement of the biodegradable polymers. The developed methodology consists of a standard conventional injection moulding process, on which a solid blowing agent based on carboxylic acids is used to generate the foaming of the bulk of the moulded part. The proposed route allows for the production of scaffolds with a compact skin and a porous core, with promising mechanical properties. By using the developed method it is possible to manufacture biodegradable polymer scaffolds in an easy (melt-based processing) and reproducible manner. The scaffolds can be moulded into complex shapes, and the blowing additives do not affect the non-cytotoxic behaviour of the starch-based materials. The materials produced using this method were evaluated with respect to the morphology of the porous structure, and the respective mechanical properties and degradation behaviour. It was demonstrated that it is possible to obtain, by a standard melt based processing route, 3D scaffolds with complex shapes that exhibit an appropriate morphology, without decreasing significantly the mechanical properties of the materials. It is believed that the optimisation of the proposed processing methodology may lead to the production of scaffolds that might be used on the regeneration of load-bearing tissues.

This work explores the dependence of the inverse temperature transition of elastin-like polymers (ELPs) on the amino-acid sequence, i.e., the amino-acid arrangement along the macromolecule and the resulting linear distribution of the physical properties (mainly polarity) derived from it. The hypothesis of this work is that, in addition to mean polarity and molecular mass, the given amino-acid sequence, or its equivalent--the way in which polarity is arranged along the molecule--is also relevant for determining the transition temperature and the latent heat of that transition. To test this hypothesis, a set of linear and di- and triblock ELP copolymers were designed and produced as recombinant proteins. The absolute sequence control provided by recombinant technologies allows the effect of the amino-acid arrangement to be isolated while keeping the molecular mass or mean polarity under strict control. The selected block copolymers were made of two different ELPs: one exhibiting temperature and pH responsiveness, and one exhibiting temperature responsiveness only. By changing the arrangement and length of the blocks while keeping other parameters, such as the molecular mass or mean polarity, constant, we were able to show that the sequence plays a key role in the smart behavior of ELPs.

The possibility of obtaining different self-assembled nanostructures in reversible systems based on elastin-like block corecombinamers is explored in this work. The results obtained show how an evolution from a more common micellar structure to a hollow vesicle can be attained simply by changing the block arrangements and lengths, even when other molecular properties, such as molecular weight or mean polarity, remain essentially unchanged. This work sheds light on the possibility of obtaining hollow nano-objects, based on elastin-like recombinamers, which can assemble and disassemble in response to a change in their surroundings. This kind of system can be an example of how high precision in the genetic production of synthetic macro-molecules can be used, on an exclusive basis, to control the shape and size of their derived nano-objects.

l-asparaginase (l-asparagine amino hydrolase, E.C.3.5.1.1) is an enzyme clinically accepted as an antitumor agent to treat acute lymphoblastic leukemia and lymphosarcoma. It catalyzes l-asparagine (Asn) hydrolysis to l-aspartate and ammonia, and Asn effective depletion results in cytotoxicity to leukemic cells. Microbial l-asparaginase (ASNase) production has attracted considerable attention owing to its cost effectiveness and eco-friendliness. The focus of this review is to provide a thorough review on microbial ASNase production, with special emphasis to microbial producers, conditions of enzyme production, protein engineering, downstream processes, biochemical characteristics, enzyme stability, bioavailability, toxicity and allergy potential. Some issues are also highlighted that will have to be addressed to achieve better therapeutic results and less side effects of ASNase use in cancer treatment: (a) search for new sources of this enzyme to increase its availability as a drug; (b) production of new ASNases with improved pharmacodynamics, pharmacokinetics and toxicological profiles, and (c) improvement of ASNase production by recombinant microorganisms. In this regard, rational protein engineering, directed mutagenesis, metabolic flux analysis and optimization of purification protocols are expected to play a paramount role in the near future.