Phase‐Transited Lysozyme as a Universal Route to Bioactive Hydroxyapatite Crystalline Film

Abstract

A key factor for successful design of bioactive complex, organic-inorganic hybrid biomaterials is the facilitation and control of adhesion at interfaces, as many current synthetic biomaterials are inert, lacking interfacial bio activity. In this regard, the development of a simple, unified way to bio functionalize diverse organic and inorganic materials toward biomineralization remains a critical challenge. In this report, a universal biomimetic mineralization route that can be applied to virtually any type and morphology of scaffold materials is provided to induce nucleation and growth of hydroxyapatite (HAp) crystals based on phase-transited lysozyme (PTL) coating. Surface-anchored abundant functional groups in the PTL enrich the interface with strongly bonded calcium ions, facilitating the formation of HAp crystals in simulated body fluid with the morphology and alignment being similar to that observed in natural HAp in mineralized tissues. By the adhesion of amyloid contained in the PTL, such protein assembly could readily integrate HAp on ceramics, metals, semiconductors, and synthetic polymers irrespective of their size and morphology, with robust bonding stability and corresponding ultralow wear extent under normal bone pressure. This strategy successfully improves the in vivo osteoconductivity of Ti-based implant, underpinning the expectation for such biomaterial in future biointerface and tissue engineering.

Amyloid‐Like Rapid Surface Modification for Antifouling and In‐Depth Remineralization of Dentine Tubules to Treat Dental Hypersensitivity

“…2019, 31,1903973 www.advmat.de www.advancedsciencenews.com that the PTL nanofilm had excellent interfacial bioactivity to induce in situ interfacial biomineralization of HAp in simulated body fluid, [34] the remineralization inside the lyso-PEG nanofilm-coated DTs could be rationally expected (Figure 5a). Due to the small size of lyso-PEG oligomers (around 30 nm), oligomers could easily access into the deep regions of DTs and the lyso-PEG coating formed in minutes, offering a sample and effective route to build active layer inside DTs.…”

“…[35] Consistently, Raman analysis of the modified surface of the DTs also indicated that the regenerated mineral was HAp rather than other calcium phosphate ( Figure S21, Supporting Information), showing typical HAp peaks of OPO vibration at 586 cm −1 and PO stretching vibration at 960 cm −1 , being consistent with dentin. [40] However, in contrast to conventional HAp growth on a surface, the remineralization on the lyso-PEG coating did not weaken the stability of mineral layers, because the lyso-PEG coating provided a robust interface between HAp crystals and underlying substrate due to the robust amyloid-mediated interfacial adhesion, in which the cumulative weight loss and the wear rate of the HAp on the amyloid-like lysozyme nanofilm-coated Ti were ten times smaller than those on the sample of HAp growth on blank Ti; [34] moreover, the HAp on the amyloid-like lysozyme nanofilm-coated Ti remained stable after strong ultrasonication (50 kHz, 200 W) for 1 h or the peeling utilizing a commercial 3 m Scotch adhesive tape to have an adhesive strength higher than 1.23 N cm −1 . Notably, the minerals precipitating within the tubules were located more than 60 ± 5 µm beneath the surface, which was at least six times deeper than that in previous reports.…”

“…[36] The transverse sections of the lyso-PEG-coated dentins further reflected that the tubules were completely occluded by elongated mineral crystals even after the ultrasonic treatment (10 min) (Figure 6a-c). [34] These reported results thus suggested that the amyloid-like lysozyme nanofilm could work as robust glue to hold a huge potential application on creating functional organic-inorganic hybrid biomaterials with excellent interfacial bonding stability. [4,5,37,38] For instance, the current clinical products, such as Green Or, Hybrid Coat, Gluma Desensitizer, Duraphat ( Figure S22, Supporting Information), and 3M single bond universal adhesive ( Figure S23, Supporting Information), only covered the dentin surface with zero occluded depth inside the DTs.…”

“…[4,5,37,38] For instance, the current clinical products, such as Green Or, Hybrid Coat, Gluma Desensitizer, Duraphat ( Figure S22, Supporting Information), and 3M single bond universal adhesive ( Figure S23, Supporting Information), only covered the dentin surface with zero occluded depth inside the DTs. [34] This is because that the surface of the amyloidlike lysozyme nanofilm was enriched in functional groups, such as carboxyl, hydroxyl and amino groups, which supported the chelation of calcium or phosphate ions. From this test, the lyso-PEG-coated dentins after remineralization exhibited similar air blockage to that exhibi ted by dentins coated with Green Or (almost 100 kPa); however, after removing the mineral layer on the dentin surfaces of these two groups by strong ultrasonication, the dentin coated with Green Or showed a significant decrease in air blockage (the SEM images in Figure S24 , Supporting Information also reflected the breaking down of Green Or coating), while the air blockage for the lyso-PEG-coated dentin did not change obviously.…”

“…The superior occlusion capability of lyso-PEG compared to that of conventional products was further supported by the permeability test of the occluded dentins (Figure 6f,g). [34] Moreover, it has been reported that the functional group (COC) in the PEG was also able to coordinate with calcium ions. This result may also imply that in-depth occlusion is a key to the long-term curing of DH, [39] especially for the resistance of mechanical destabilization.…”