Material and Biological Properties of Self-Assembling Peptide Hydrogel Combinations for Use in Dental Pulp Regeneration

Saturday, October 14, 2023

1:30 PM – 1:45 PM PDT

Location: 332 (Center, Level 3)

Presenting Author(s)

Αlexandra Griffith

PhD Candidate
New Jersey Institute of Technology
Waldwick, New Jersey, United States

Co-Author(s)

JD

Joseph Dodd-o (he/him/his)

Graduate Student
New Jersey Institute of Technology
Newark, New Jersey, United States

Co-Author(s)

JM

Josuel Morel (he/him/his)

Undergraduate Student
New Jersey Institute of Technology
Nashville, Tennessee, United States

Co-Author(s)

ES

Emi Shimizu

Professor
Rutgers University, United States
CC

Carla Cugini, PhD

Assistant Professor
Rutgers School of Dental Medicine

Last Author(s)

Vivek Kumar, PhD

Associate Professor
New Jersey Institute of Technology
Newark, New Jersey, United States

Introduction:: Root canals are a painful and expensive invasive procedure performed on 15 million Americans annually. While effective in alleviating patient symptoms, there are substantial consequences of the standard Gutta-Percha procedure, including loss of functional dental pulp, increased risk of tooth failure, and risk of secondary infection. Secondary infection is a notable risk, associated with pathogenic oral bacteria such as S. mutans and E. faecalis. We have developed a self-assembling peptide (SAP) nicknamed K6 (KKKKKKSLSLSLSLSLSLKKKKKK) that preferentially disrupts the bacterial membrane. However, the mechanical properties of the peptide in aqueous solutions have yet to be tailored to the application, limiting the potential as a pathology correcting AND regenerative material. To augment the regenerative potential of the hydrogel, we have made composite hydrogels consisting of K6 and an ECM mimetic self-assembling peptide K1 (KSLSLSLSLSLSLK). Additional SAP combinations are also being investigated with an angiogenic peptide termed SLan (KSLSLSLSLSLSLKGKLTWQELYQLKYKGI) which has been noted to increase dental pulp regeneration. K1, and K6 were investigated to augment the regenerative potential of the SLan peptide hydrogel. We observed a nonlinear change in mechanical properties with increasing proportions of K6. Additional nonlinear changes were observed in the efficacy against Gram positive bacterial species, with and without biofilm protection. Our results suggest an engineerable peptide hydrogel that can be compounded to tailor to the individual patient, allowing for platform material solution for replacement of infected pulp and subsequent tissue regeneration.

Materials and Methods:: K6 and K1 were synthesized using solid phase peptide synthesis using FMOC chemistry. Purification was performed using high performance liquid chromatography, and identity of the amino acid sequence was performed using MALDI. The peptides were solvated in isotonic phosphate buffered saline at various molarities depending on experimental conditions. Combinations were performed with 5 minutes of high-speed vortex mixing to distribute the 2 peptides.

The peptide fibers were spin coated on a mica disc and imaged with a Bruker Atomic Force Microscope. Investigation of the secondary structure was performed using circular dichroism with an Olis Spectrometer. S. mutans were grown in the presence of peptide combinations and antimicrobial efficacy was measured based on biofilm formation and metabolic activity. Oscillatory rheometric analysis of the peptides was performed using a TA Instruments DA-2 rheometer. Subcutaneous implants were performed on Wistar rats and explanted after 7 days.

Results, Conclusions, and Discussions:: There was a nonlinear reduction in mechanical stiffness (measured as the storage modulus at < 10% amplitude) with increasing K6 concentration in peptide combinations of K1:K6. Fiber length was also attenuated with increasing K6 concentration, again in a nonlinear relationship. Combinations of SLan and K6 were seen to retain their characteristic antiparallel β-sheets by circular dichroism. Significant inhibition of metabolic activity was observed in peptide combinations of K1:K6 where K6 was greater than 50% molar ratio. All combinations of K1 and K6 significantly reduced biofilm biomass.
This demonstrates a potential new modality to engineer self-assembling peptide hydrogels to specifically serve the niche and pathology it is designed to address. The nonlinear relationship between bioactive peptide concentration, its efficacy on the target, and its structural and mechanical properties provide researchers with a new opportunity to tailor the properties of the peptide hydrogel. Conservation of the bioactive properties of the bioactive peptide also allow researchers to potentially combine different bioactive mimics within the composite matrix. This is the subject of future work to be performed by our team.

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