Functionalization of Recombinant Amelogenin Nanospheres Allows Their Binding to Cellulose Materials

Nanobiopolymers Fabrication and Their Life Cycle Assessments

Living organisms produced nanopolymers (nanobiopolymers for short), such as nanocellulose, nanochitin, nanosilk, nanostarch, and microbial nanobiopolymers, having received widely scientific and engineering interests in recent years. Compare with petroleum-based polymers, biopolymers are sustainable and biodegradable. The unique structural features that stem from nanosized effects, such as ultrahigh aspect ratio and length-diameter ratio, further endow nanobiopolymers with high transparence and versatile processability. To fabricate these nanobiopolymers, a variety of mechanical, chemical, and synthetic biology techniques have been developed. The applications of the isolated nanobiopolymers have been extended from polymer fillers into wide emerging high-tech fields, such as biomedical devices, bioplastics, display panels, ultrafiltration membranes, energy storage devices, and catalytic supports. Accordingly, in the review, the authors first introduce isolation techniques to fabricate nanocellulose, nanochitin, nanosilk, and nanostarch. Then, the authors summarized the nanobiopolymers produced from biosynthetic pathway, including microbial polyamides, polysaccharides, and polyesters. On the other hand, most of these techniques require high energy consumption and usage of chemical reagents. In this regard, life cycle assessment offered a quantitative route to precisely evaluate and compare environmental benefits of different artificial isolation approaches, which are also summarized in the second section of the review.

Recombinant amelogenin regulates the bioactivity of mouse cementoblasts in vitro

Amelogenin (AMG) is a cell adhesion molecule that has an important role in the mineralization of enamel and regulates events during dental development and root formation. The purpose of the present study was to investigate the effects of recombinant human AMG (rhAMG) on mineralized tissue-associated genes in cementoblasts. Immortalized mouse cementoblasts (OCCM-30) were treated with different concentrations (0.1, 1, 10, 100, 1000, 10,000, 100,000 ng · mL^-1) of recombinant human AMG (rhAMG) and analyzed for proliferation, mineralization and mRNA expression of bone sialoprotein (BSP), osteocalcin (OCN), collagen type I (COL I), osteopontin (OPN), runt-related transcription factor 2 (Runx2), cementum attachment protein (CAP), and alkaline phosphatase (ALP) genes using quantitative RT-PCR. The dose response of rhAMG was evaluated using a real-time cell analyzer. Total RNA was isolated on day 3, and cell mineralization was assessed using von Kossa staining on day 8. COL I, OPN and lysosomal-associated membrane protein-1 (LAMP-1), which is a cell surface binding site for amelogenin, were evaluated using immunocytochemistry. F-actin bundles were imaged using confocal microscopy. rhAMG at a concentration of 100,000 ng · mL^-1 increased cell proliferation after 72 h compared to the other concentrations and the untreated control group. rhAMG (100,000 ng · mL^-1) upregulated BSP and OCN mRNA expression levels eightfold and fivefold, respectively. rhAMG at a concentration of 100,000 ng · mL^-1 remarkably enhanced LAMP-1 staining in cementoblasts. Increased numbers of mineralized nodules were observed at concentrations of 10,000 and 100,000 ng · mL^-1 rhAMG. The present data suggest that rhAMG is a potent regulator of gene expression in cementoblasts and support the potential application of rhAMG in therapies aimed at fast regeneration of damaged periodontal tissue.

A protein with its roots in dental development stimulates the proliferation and gene expression of cells linked to regeneration. Amelogenin is a mediator of enamel and tooth root formation, and the main component of a recently-developed medicine for periodontal regeneration. An international research group led by Sema Hakki, of Selcuk University, Turkey, has now elucidated the effects of amelogenin on cementoblasts, a type of cell responsible for producing the vital, mineralized layer on surface of the tooth root. Hakki’s team found that the bacteria-derived amelogenin increased the rate of mouse cementoblast proliferation and mineralization in vitro, and increased the expression of genes related to bone and tissue generation. The team also demonstrated the presence of a likely amelogenin receptor on the cells used in their study. These findings support further investigation into amelogenin’s therapeutic potential.

Cloning and Expression Analysis of Human Amelogenin in Nicotiana benthamiana Plants by Means of a Transient Expression System

Enamel is the covering tissue of teeth, made of regularly arranged hydroxyapatite crystals deposited on an organic matrix composed of 90% amelogenin that is completely degraded at the end of the enamel formation process. Amelogenin has a biomineralizing activity, forming nanoparticles or nanoribbons that guide hydroxyapatite deposit, and regenerative functions in bone and vascular tissue and in wound healing. Biotechnological products containing amelogenin seem to facilitate these processes. Here, we describe the production of human amelogenin in plants by transient transformation of Nicotiana benthamiana with constructs carrying synthetic genes with optimized human or plant codons. Both genes yielded approximately 500 µg of total amelogenin per gram of fresh leaf tissue. Two purification procedures based on affinity chromatography or on intrinsic solubility properties of the protein were followed, yielding from 12 to 150 µg of amelogenin per gram of fresh leaf tissue, respectively, at different purity. The identity of the plant-made human amelogenin was confirmed by MALDI-TOF-MS analysis of peptides generated following chymotrypsin digestion. Using dynamic light scattering, we showed that plant extracts made in acetic acid containing human amelogenin have a bimodal distribution of agglomerates, with hydrodynamic diameters of 22.8 ± 3.8 and 389.5 ± 86.6 nm. To the best of our knowledge, this is the first report of expression of human amelogenin in plants, offering the possibility to use this plant-made protein for nanotechnological applications.