Abstract
Hierarchically porous biocompatible Mg-Al-Cl-type layered double hydroxide (LDH) composites containing aluminum hydroxide (Alhy) have been prepared using a phase-separation process. The sol-gel synthesis allows for the hierarchical pores of the LDH-Alhy composites to be tuned, leading to a high specific solid surface area per unit volume available for high-molecular-weight protein adsorptions. A linear relationship between the effective surface area, SEFF, and loading capacity of a model protein, bovine serum albumin (BSA), is established following successful control of the structure of the LDH-Alhy composite. The threshold of the mean pore diameter, Dpm, above which BSA is effectively adsorbed on the surface of LDH-Alhy composites, is deduced as 20 nm. In particular, LDH-Alhy composite aerogels obtained via supercritical drying exhibit an extremely high capacity for protein loading (996 mg/g) as a result of a large mean mesopore diameter (>30 nm). The protein loading on LDH-Alhy is >14 times that of a reference LDH material (70 mg/g) prepared via a standard procedure. Importantly, BSA molecules pre-adsorbed on porous composites were successfully released on soaking in ionic solutions (HPO4(2-) and Cl(-) aqueous). The superior capability of the biocompatible LDH materials for loading, encapsulation, and releasing large quantities of proteins was clearly demonstrated.
Highlights
Protein immobilization on solid surfaces is of relevance to a wide range of research areas, with potential applications in biotechnology and physiology.[1]
The hierarchically porous layered double hydroxide (LDH)−aluminum hydroxide (Alhy) composites were prepared via hydrolysis and condensation reactions of metal salts by alkalinization in the presence of PO according to our previously published method.[15]
The capacity for protein loading was investigated with bovine serum albumin (BSA) as a model protein, which revealed the existence of a threshold on the smaller critical mesopore size required to accommodate BSA molecules to be ca
Summary
Protein immobilization on solid surfaces is of relevance to a wide range of research areas, with potential applications in biotechnology and physiology.[1]. A total of 52% of BSA desorbed in 72 h from A-LDH in the case of using HPO42− as a competitive anion, which is comparable to that from Com-LDH (49%) This result confirms that the protein desorption and adsorption take place with a large capacity for the present LDH−Alhy composites. These results demonstrate the possibilities of encapsulation and extended release of various protein molecules with a high capacity based on tunable hierarchically porous LDH. Combining LDH materials with various selectivities toward different molecules/ions will further open up biocompatible separation and purification required for biomedical applications.[42]
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