Effect of additives on encapsulation efficiency, stability and bioactivity of entrapped lysozyme from biodegradable polymer particles

Abstract

Low encapsulation efficiency, incomplete and erratic release profiles are the most common features of controlled released protein delivery systems employing biodegradable polymers. In the present study, lysozyme as a model protein was encapsulated in biodegradable microspheres using solvent evaporation method and the effect of amphiphilic stabilizer, a basic salt and a lyoprotectant on microparticle formulation was evaluated. Incorporation rat serum albumin (RSA) in the internal aqueous phase during emulsion increased the encapsulation efficiency of lysozyme and maintained the bioactivity. Use of NaHCO3 improved the encapsulation efficiency of lysozyme from 15-94%, but at the cost of reduced in vitro release characteristics. Incorporation of both RSA and NaHCO3 improved the bioactivity of lysozyme and decreased burst release of the protein from the polymer particle, but reduced the encapsulation efficiency from 90-70%. Addition of sucrose in the internal aqueous phase lowered the encapsulation efficiency which was restored by its addition in the external aqueous phase. Maintenance of internal aqueous phase pH close to the iso-electric point of the protein and osmotic balance between the internal aqueous phase and the external aqueous phase during solvent evaporation method helped in better encapsulation of the protein drug. In vitro release of the lysozyme correlated with the effect of different excipients on entrapment in polymer matrix. Entrapment efficiency as high as 76%, low burst effect and high bioactivity of the entrapped lysozyme was observed from the polymer particles. Use of RSA, sucrose and NaHCO3 helped in a co-operative way towards the formulation of particles entrapping bioactive lysozyme.

Evaluation of biodegradable polyester-co-lactone microparticles for protein delivery

“…Enzyme activity before and after encapsulation and upon release can be monitored to investigate the effect of these processes on biological activity. Many researchers have estimated the bioactivity of LS by measuring the rate of degradation of Micrococcus luteus cells 25,46 . However, this method is not always reproducible because of the dependence on the ionic strength of the medium 47,48 .…”

“…This was calculated from the ratio of enzyme concentration determined from enzyme activity and the total enzyme concentration as determined by UV spectroscopy using the methods described below 25 .…”

Design of Protein‐Releasing Chitosan Channels

“…Encapsulation efficiency of alkaline phosphatase-loaded microspheres was 80.3 AE 1.3%, which is comparable to other optimized PLGA double emulsion systems. [30][31][32][33] High encapsulation efficiencies result in greater drug content in the microsphere product and minimize losses during the manufacturing process.…”

“…44 Although the time frame for release in this study was 3 months, the release rates for specific drug applications can be tuned to be shorter or longer by modifying various process parameters during microsphere preparation. These include changing the polymer lactide/glycolide ratio 45 or molecular weight, 46 introducing copolymers such as polycaprolactone 47 or additives such as poly(ethylene glycol), 33 or by simply altering microsphere size. 48 PLGA microsphere systems have been shown to be capable of degradation over timescales of a few weeks 46,49 to several months.…”

Role of Polymeric Excipients on Controlled Release Profile of Glipizide from PLGA and Eudragit RS 100 Nanoparticles

“…From previous studies it was concluded that by adjusting the phase volume ratio (Organic phase and External aqueous phase) and energy input in terms of sonication/homogenization, different size polymeric particles can be generated 23,26 . In this study the sonication time (40 % duty cycle for 3 minute) was increased and the phase volume ratio adjusted ( 26,28,29 . This suggested that these excipients mostly stabilize the aqueous/organic emulsion droplet during primary emulsification step of particle formulation.…”