University of Southern California Dissertations and Theses

Amelogenin peptides for biomimetic remineralization of enamel and dentin

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Amelogenin peptides for biomimetic remineralization of enamel and dentin

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Abstract (if available)

Abstract Mature enamel is a highly mineralized biocermaic that is composed of bundles of hydroxyapatite crystals (HAP) called enamel rods. Rods are further woven together in an intricate architecture providing exquisite resilience and wear resistance to the tooth structure. The interplay between the organic macromolecules in enamel matrix and mineral ions can lead to the formation of hierarchical structures composed of well-oriented HAP crystals. Unlike bone, enamel is acellular and lacks the capacity to remodel or regenerate. The gradual discovery of functional domains in native enamel matrix proteins such as amelogenin has enabled the design of smart bioinspired peptides for tooth enamel mimetics and repair. The aim of my study was to design bioinspired amelogenin-derived peptides (P26 and P32) with conserved functional domains for enamel and dentin remineralization. ❧ Materials and Methods: The secondary structure and assembly of the peptides were characterized using circular dichroism (CD) and transmission electron microscopy (TEM). Peptide-mediated mineralization experiments in vitro were observed using TEM and in situ Raman spectroscopy. Peptide-collagen assembly and peptide-collagen mineralization events in vitro were investigated using transmission electron microscopy (TEM). Leucine-rich amelogenin peptide (LRAP) and full-length recombinant amelogenin (rP172) were used in several experiments as positive control. ❧ Ex vivo experiments were conducted on longitudinally-sectioned enamel slices and transversally sectioned dentin discs. Peptide-coated tooth slices were immersed in 5 ml of artiﬁcial saliva at pH 7.0 at 37 ℃ for up to 7-10 days. The microstructure, orientation, elemental composition and mechanical performance of the newly formed HAP layers on enamel and dentin were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and nanoindentation tests. ❧ Results: Circular Dichroism revealed that both peptides exhibited a disordered conformation similar to full-length amelogenin. Peptides P26 and P32 demonstrated the formation of dispersed, characteristic nanospherical particles. TEM images showed that addition of peptides to CaP resulted in the formation of smaller, thin, plate-like HAP crystals of relatively uniform size distribution after 24 h of ripening, consistent with the findings of in situ Raman spectroscopy. Presence of peptide also accelerated apatite nucleation as seen on the TEM grid surface. Peptide assemblies associated with collagen fibrils were seen as linearly dispersed nanospheres, in single numbers or in aggregates, aligned closely along the surface of collagen fibrils. Mineralization of collagen fibrils in the presence of P26 after 2.5 h gradually transformed it to smooth electron-dense fibrils with diffraction data (SAED) showing rings characteristic of HAP. Ex vivo experiments on peptide-treated tooth slices (enamel and dentin) showed the precipitation of HAP crystals with increased mechanical properties of surface apatite layers. For P-26 treated enamel slices, SEM and XRD images showed formation of multiple layers of oriented HAP on repeated peptide application with improved attachment to native enamel. For P-26 treated dentin discs, there was a marked occlusion of open dentinal tubules, precipitation of plate-like HAP crystals on the surface and mineral deposition on exposed collagen fibers. ❧ Conclusion: We report a bottom-up biomineralization strategy showing that amelogenin peptides with conserved functional domains can effectively regulate the growth of HAP crystals on enamel and dentin slices with increased adhesion and increased mechanical properties (hardness and modulus) of the repaired layers. Hence, an in-depth understanding of the calcified dental tissues and variations in their intrinsic composition and hierarchy can lead to the biological mimicry of next-generation biomaterials that can be developed specifically to address enamel or dentin defects.

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Asset Metadata

Creator Mukherjee, Kaushik (author)

Core Title Amelogenin peptides for biomimetic remineralization of enamel and dentin

Contributor Electronically uploaded by the author (provenance)

School School of Dentistry

Degree Doctor of Philosophy

Degree Program Craniofacial Biology

Publication Date 04/25/2019

Defense Date 02/27/2019

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag amelogenin,biomineralization and biomimetics,collagen mineralization,dentin,enamel remineralization,OAI-PMH Harvest,peptide

Format application/pdf (imt)

Language English

Advisor Moradian-Oldak, Janet (committee chair), Duarte, Sillas (committee member), Nutt, Steven (committee member), Paine, Michael (committee member), Phark, Jin-Ho (committee member)

Creator Email kaushikm112@gmail.com,kmukherj@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c89-144317

Unique identifier UC11676712

Identifier etd-MukherjeeK-7245.pdf (filename),usctheses-c89-144317 (legacy record id)

Legacy Identifier etd-MukherjeeK-7245.pdf

Dmrecord 144317

Document Type Dissertation

Format application/pdf (imt)

Rights Mukherjee, Kaushik

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the a...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA