PLGA polymers

It has also been reported that antigen delivery to DCs via PLGA particles increased the amount of protein that escaped from endosomes into the cytoplasm. How proteins or peptides encapsulated within PLGA particles become accessible to the cytoplasm is still not clear. It is suggested that the gradual acidification of endosomes leads to protonation of the PLGA polymer, resulting in enhanced hydrophobicity and attachment and rupture of the endosomal membrane [147]. 

Polyesters, specifically polylactides and poly(lactide-co-glycolide)s have played a critical role in the development of polymer-based CR technologies. The biocompatibility and the well-established safety profiles of PLA and PLGA polymers have made them the polymer of choice for CR applications. However the off-patent status of these polymers makes them freely available for research in industry as well as academia. This has led to a vast number of patents covering various applications of these polymers within the drug delivery sector. Due to these issues, very limited scope remains to utilize these polymers to reformulate generic, off-patent drugs. 

A recent novel approach uses the PLGA polymer as a sustained-release coating on budesonide dry powders. Talton et al. showed that these coated particles conferred a statistically significant increase in pulmonary targeting in rats compared with uncoated budesonide powders [101], Another approach uses a wax coating to control particle dissolution. Pillai et al. produced paraffin wax-coated fluores-... 

Figure 4.12 Synthesis and in vivo degradation of PLGA polymers...

In contrast to bulk-eroding PLA/PLGA polymers, the polyanhydride undergoes surface erosion. The thin-disk type morphology of the wafer confers a high surface-to-volume ratio on the implant, so that the total surface area of the implant is kept almost constant over the time of polymer degradation, which facilitates a constant release of carmustine with time. 

Despite the extensive use of PLGA polymers in the microencapsulation arena, it has been found through decades of research that the PLGA microparticle systems are not universally suited for different applications. One of the limitations in the prevalent PLGA systems is that bulk hydrolysis of the polymer induces acidification of microenvironment of the microparticles, which can be detrimental to various payloads such as proteins and nucleic acids. In addition, their drug release kinetics are not readily tunable and, thus, are inappropriate for specific applications.f ... 

It has also been noticed that the sensitive drugs can be denatured or degraded during the long-term release period. There are different proofs that suggest microparticles made of PLGA polymers generate... 

Rasiel investigated triptorelin release profiles from lipospheres made from L-PLA, PLGA 50 50, and PLGA 75 25 [35], Although both PLGA polymers showed a burst release within the first 24 h, L-PLA released the peptide for over 30 d (Figure 4.6). 

Ferdous, A.J. Stembridge, N.Y Singh, M. Role of monensin PLGA polymer nanoparticles and liposomes as potentiator of ricin A immunotoxins in vitro. J. Control. Release 1998, 50 (1-3), 71-78. 

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