Lysozyme specific aptamer immobilized MCM-41 silicate for single-step purification and quartz crystal microbalance (QCM)-based determination of lysozyme from chicken egg white

• Lysozyme specific aptamer was immobilized on MCM-41 silica particles.
• Lysozyme adsorption and purification has been studied as a function of salt and pH.
• The maximum lysozyme adsorption capacity was found to be 36.8 mg/g.
• Aptamer affinity system was specific to lysozyme compared to other tested proteins.
• The same aptamer squence was also used for construction of QCM biosensor.

In the present study, MCM-41 silica particles were functionalized with 3-aminopropyltriethoxysilane (APTES) and characterized by FTIR, SEM, TEM and, Brunauer–Emmett–Teller (BET) analysis. A lysozyme specific aptamer was then immobilized onto amine functionalized MCM-41 particles via glutaraldehyde coupling, which were used for adsorption and purification of lysozyme. The effect of various parameters including pH, adsorbent dosage and lysozyme concentration on the lysozyme specific aptamer immobilized silica particles was evaluated. Efficiency of aptamer-silica particles in the purification of lysozyme from diluted chicken egg white was also realized. The optimal adsorption condition was in phosphate buffer (50 mmol L−1, pH 7.0) and the lysozyme adsorption capacity was 36.8 mg g−1 polymer. Increasing the initial lysozyme concentration and temperature had a positive effect on the binding capacity, whereas increasing the ionic strength resulted in the opposite effect. The recovery of adsorbed lysozyme by elution with glycine buffer (0.2 mol L−1, pH 2.0) was about 93%. Additionally, proteins with different isoelectric points (e.g. lysozyme, albumin, cytochrome c and hemoglobin) were used as model proteins to investigate the selectivity of the lysozyme binding aptamer. The lysozyme aptamer was used in the purification of lysozyme from diluted chicken egg white, which was verified by a single SDS-PAGE band. The reusability studies showed that, about 87% of the initial adsorption capacity of the aptamer immobilized particles could be maintained after 20 cycles of purification. Finally, the specific interaction between lysozyme specific aptamer sequences and lysozyme was investigated by quartz crystal microbalance (QCM) biosensor for determination of lysozyme in the egg samples.

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