The mechanism of catalase loading into porous vaterite CaCO₃ crystals by co-synthesis

Abstract

Porous vaterite CaCO 3 crystals are nowadays extensively used as high-capacity bio-friendly sacrificial templates for the fabrication of such protein-containing nano-and micro-particles as capsules and beads. The first step in the protein encapsulation is performed through loading of the protein molecules into the crystals. Co-synthesis is one of the most useful and simple methods proven to effectively load crystals with proteins; however, the loading mechanism is still unknown. To understand the mechanism, in this study, we focus on the loading of a model protein catalase into the crystals by means of adsorption into pre-formed crystals (ADS) and co-synthesis (COS). Analysis of the physico-chemical characteristics of the protein in solution and during the loading and simulation of the protein packing into the crystals are performed. COS provides more effective loading than ADS giving protein contents in the crystals of 20.3 and 3.5 w/w%, respectively. Extremely high loading for COS providing a local protein concentration of about 550 mg mL À1 is explained by intermolecular protein interactions, i.e. by adsorption of the aggregates into the crystals. We believe that this study will be useful for protein encapsulation through CaCO 3 crystals using the COS method.

Naturally derived nano- and micro-drug delivery vehicles: halloysite, vaterite and nanocellulose

“…70 The FDA has approved the use of CaCO 3 (without specifying its polymorphism) as a food additive ( §582.1191), a dietary supplement ( §582.5191), a direct food substance ( §184.1191), and a colour additive for food ( §73. 70 to macromolecules (proteins, 77,81,82 growth factors, 83 genes 84,85 ) and inorganic nanoparticles (Ag, 86 ). Importantly, multicomponent encapsulation into VCC is also possible and has been reported (e.g.…”

“…Adsorption represents the most ''mild'' method suitable for the encapsulation of labile molecules prone to aggregation, denaturation and the loss of activity in aggressive media. 81,82,94 In contrast, for co-precipitation mixing of drug solution with precursor salts results in more effective entrapment and homogeneous distribution of the drug inside the crystals during their growth. However, because of more harsh conditions of crystal growth (high ionic strength and elevated pH), much higher encapsulation efficiencies may be accompanied by a partial loss of activity for sensitive macromolecules, 81 while small drugs are usually unaffected.…”

The Stability Maintenance of Protein Drugs in Organic Coatings Based on Nanogels

“…The mean diameter of PAAM-n(catalase) was~35 nm which was much higher than that of native catalase (~10 nm) [30] ( Figure 1A). The zeta potential of native catalase in PBS solution was negative (~−14 mV) as the isoelectric point was at~pH 5.4 [31]. Due to the shielding effect of the polymeric shell and the existence of poly(APM), the zeta potential of PAAM-n(catalase) was positive (~10 mV).…”

Inter-protein interactions govern protein loading into porous vaterite CaCO3 crystals

“…51,52 Notably, co-synthesis often results in higher loading efficiencies but lower residual protein activities. 51,53 Nowadays it is widely believed that the adsorption of macromolecules onto the porous surface of CaCO 3 crystals is presumably governed by electrostatic protein-CaCO 3 interactions, which has been proposed for polyelectrolytes, 54,55 DNA 56 and globular proteins. 57,58 Modulation of the strength of electrostatic interactions via the doping of CaCO 3 crystals with highly charged polymer matrices has been reported to enhance protein entrapment.…”

“…This has been explained by protein aggregation in the presence of Ca 2+ . 53 Another demonstrative example is the adsorption of the linear polymer poly(acrylic acid) on the CaCO 3 surface, which has been characterized by drastically different Gibbs energies ranging from À45 kJ mol À1 61 up to +395 kJ mol À1 62 in the corresponding studies. Importantly, some studies report a direct correlation 57 between the protein net charge and adsorption capacities, while others report no evidence of the correlations.…”