Current approaches to stabilising and analysing proteins during microencapsulation in PLGA

Abstract

Encapsulation of biomacromolecules in polyester micro- and nano-particles is now a routine procedure in many laboratories for achieving controlled and targeted delivery strategies. Objectives: Proteins are notoriously difficult to encapsulate without some degree of unfolding and loss of bioactivity, and this is despite around two decades of research. A case by case analysis appears necessary when determining which mechanism, generally unfolding at the emulsion interface or acidification of the particle interior, is most detrimental. The transient nature of the emulsion systems makes in situ, real-time analysis of interfacial events difficult, necessitating interpretation from model interfacial systems or analysis post-fabrication. The review will focus on: i) the emulsification efficiency of proteins, cf. interfacial adsorption; ii) current excipients and techniques used to stabilise proteins, outlining work towards the oral delivery of insulin as a case study; iii) analytical techniques used to characterise encapsulated protein. There appears to be a recent trend towards the stabilization of proteins via direct complexation with polymers but, in contrast, emulsion techniques are emerging which err away from the use of stabilisers and/or excipients. A number of spectroscopic and spectrometric methods have found new application to the study of protein integrity in microspheres

Growth Factor-Loaded Microparticles for Tissue Engineering: The Discrepancies of In Vitro Characterization Assays

“…Finally, as stated by Walle et al, while the use of additives is very popular, a clear need for these additives has not yet emerged and case-by-case basis studies are required. 35 In terms of microparticle preparation, we have already established that electrospraying is an innovative emerging technique with enhanced capacity for reproducible protein encapsulation and delivery compared with traditional encapsulation techniques. [22][23][24][25] Electrosprayed particles present superior characteristics compared with particles from traditional water-in-oil emulsion-based techniques due to a gentler technique and superior control over the particles' features.…”

Biodegradable insulin-loaded PLGA microspheres fabricated by three different emulsification techniques: Investigation for cartilage tissue engineering

“…During preparation of the insulin-loaded microspheres the protein is exposed to a range of damaging conditions that frequently cause alterations in the protein structure and a loss of bioactivity, including high shear forces during vortex mixing, organic solvents, organic-aqueous interfaces, hydrophobic contacts between the protein and the polymer and protein dehydration during freeze drying [48][49][50]. In particular, the w/o/w encapsulation technique would be expected to damage the protein structure because of the high interfacial area during the first w/o emulsification step [51,52].…”

Biomaterials to Enhance Stem Cell Function in the Heart

“…53,65 However, polymerization of PLGA is a harsh chemical process that can lead to denaturation of proteins and that restricts seeding of cells after polymerization has been completed. 66 Therefore, PLGA has been used primarily to generate tissue engineered scaffolds. A major advantage of PLGA scaffolds is that they can be used for many different applications; an example is printing of a pattern of 20-m-wide fibronectin strips on PLGA sheets.…”