Injectable Biopolymers

Keywords Gene therapy, tissue reconstruction, injectable biopolymers, polymeric drug-elut-ing stents, cardiovascular polymers... 

Jeng, L., Olsen, B.R., Spector, M. Engineering endostatin-expressing ceutilaginous constructs using injectable biopolymer hydrogels. Acta Biomater. 8, 2203-2212 (2012)... 

This first strategy was used by Setton and coworkers to trigger the in situ formation of an ELP-based dmg depot for sustained release. Biodistribution studies of radiolabeled LLPs with a below body temperature were performed after intra-articular injection in rats [94]. Later, dmg depots of ELPs with covalently attached immunomodulator therapeutics [95] and anti-TNLa therapeutics [96] were created. Respectively, ELP[V-120] and ELP[V-60] biopolymers with a transition below body temperature were used in these studies. 

Setton and Chilkoti applied ELPs as a three-dimensional matrix to entrap chondrocytes. In their study, ELP[VsG3A2-90] with a transition temperature of 35°C at 50 mg/mL in PBS was used. This biopolymer can be used to generate a suspension with cells, which upon injection into a defect site will form a scaffold. They showed that in vitro the resulting ELP gel supported the viability of chondrocytes and the synthesis and accumulation of cartilage-specific extracellular matrix material. This suggested that ELPs indeed could be used for in situ formation... 

Branco M, Wagner N, Pochan D et al (2009) Release of model macromolecules from selfassembling peptide hydrogels for injectable delivery. Biopolymers 92 318-318... 

Capillary electrophoresis offers several useful methods for (i) fast, highly efficient separations of ionic species (ii) fast separations of macromolecules (biopolymers) and (iii) development of small volume separations-based sensors. The very low-solvent flow (l-10nL min-1) CE technique, which is capable of providing exceptional separation efficiencies, places great demands on injection, detection and the other processes involved. The total volume of the capillaries typically used in CE is a few microlitres. CE instrumentation must deliver nL volumes reproducibly every time. The peak width of an analyte obtained from an electropherogram depends not only on the bandwidth of the analyte in the capillary but also on the migration rate of the analyte. 

MAI,PI was introduced in the late 1980s and is one of the most successfully developed MS soft ionization techniques that uses the matrix assists laser ablation of sample-coated target to vaporize gas-phase ions for injection into a mass spectrometer. The advantage of MALDI is its gentleness compared with ESI and Atmospheric Pressure Chemical Ionization (APCI) and its ability to analyze the polar, nonvolatile, and large molecules. It has been very successfully used for the analysis of both biopolymers compounds and small molecular organic compounds (<1,500 Da). 

In this case the biopolymers are directly plasticized by thermomechanical means, and transformed through the classical forming technologies of the plastic industry injection-moulding, extrusion and thermoforming. These agromaterials keep a natural aspect, they are sensitive to the atmospheric conditions like wood, but they have no shape restrictions (Figure 5.20). 

Beside overloading effects, charge interaction effects play an important role in the retention behavior of polyelectrolytes [243]. In such cases, a strong dependence of the retention data on the concentration and volume of the injected polymer sample can also be observed. This phenomenon related to inter-molecular interactions complicates quantitative evaluation of distributions from FFF retention data. Such effects can be partly suppressed by the addition of an electrolyte but investigations of polyelectrolytes are still complicated. Other sample-sample interactions can significantly change the effective size of the polymer and thus also its retention behavior [456]. Such interactions are common with biopolymers as they are very often part of their biological function. 

Even then the fractionation of gram quantities will be tedious and time-consuming work if one considers that the typical amount per injection into an FFF channel is in the pg range. Nevertheless, the fractionation of mg amounts of samples is especially interesting for modern biopolymer samples, such as DNS fragments, or molecular factors which are produced in such amounts. 

In recent years starch, the polysaccharide of cereals, legumes and tubers, has acquired relevance as a biodegradable polymer and is becoming increasingly important as an industrial material (Fritz Aichholzer, 1995). Starch is a thermoplastic polymer and it can therefore be extruded or injection moulded (Balta Calleja et al, 1999). It can also be processed by application of pressure and heat. Starch has been used successfully as a matrix in composites of natural fibres (flax, jute, etc.). The use of starch in these composites could be of value in applications such as automobile interiors. An advantage of this biopolymer is that its preparation as well as its destruction do not act negatively upon the environment. A further advantage of starch is its low price as compared with conventional synthetic thermoplastics (PE, PP). 

In summary, P/A was better than A/P, and A-PP was better than A/P or P/A. These observations were also made by Chen et al. (1999b). Figure 11.6 shows the residual oil recovery factor after waterflooding. The system was as follows oil viscosity, 180 mPa s at room temperature polymer, 5000 mg/L HPAM and alkali, Na2Si04. This figure shows that A-pP was better than any sequential or single injection process. This result was also observed when a biopolymer or less-viscous oil (62 mPa s) was used. Although in this example A/P was much better than P/A, P/A was better than A/P in the case of 62 mPa s (Krumrine and Falcone, 1983). 

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