Discipline: Technology and Engineering
Beatriz Quinones-Colon - University of Puerto Rico, Mayagüez Campus
Co-Author(s): David Castilla and Jorge Almodóvar, University of Puerto Rico, Mayagüez Campus
The Layer-by-Layer (LbL) technique has quickly grown as a powerful yet simple methodology for the modification of biomaterial’s surfaces. It can improve the biocompatibility of biomaterials and render them with properties that enhance their functionality. Moreover, LbL films can serve as reservoirs for drugs or therapeutic properties. Insight on LbL film construction and characterization is important to finely tune these films for their desired application. Our work was composed of developing one through six bilayers of natural polymers chitosan (CHI) and heparin (HEP), and synthetic polymers poly ethylenimine (PEI) and poly sodium-p- styrenesulfonate (PSS) on a silicon substrate, taking into consideration their electrostatic forces by the LBL method. Multilayer combinations of HEP/CHI and PEI/PSS were prepared, from polymeric solutions in Acetate Buffer at pH 5.0. The types of rinsing solution and variations in their pH were evaluated. Experiments were performed using Acetate Buffer 0.1M or Sodium Chloride 0.15M as interlayer wash solution with a pH value of 4, 5 and 6. To understand how these layers are formed over the substrate and how they alter it, the formation of the LbL films, their physical-chemical characteristics and their thermal stability, were evaluated using Infrared Variable Angle Spectroscopic Ellipsometry (IRVASE). This is a powerful non-destructive characterization technique combining the advantages of ellipsometry and infrared spectroscopy (Fourier Transform IR). Thus, the thickness and optical constants (n, k) of multilayer coatings can be determined as well as the characteristic chemical bonds of the analyzed materials. It was observed that the type of wash solution and its pH plays an important role in the chemistry, homogeneity, and thickness of the multilayers and its variation alter the formation of the layers depending on the polymer combinations used. Bilayers rinsed with Acetate buffer at a pH of 5 showed more intense peaks than those rinsed with sodium chloride. In addition, as the amount of multilayers increase, the characteristic peaks of these polymers were more defined and their thickness increased, showing thickness between 80-150nm. It is important to analyze these polymeric nano-films and understand how they alter the surface of substrates because they would create an attractive bioactive surface over a biomaterial that would not only reduce the amount of healing time a patient needs after a biomaterial has been implanted into their body, but it would provide the cells in the body with an environment good enough to carry out their usual cellular processes.
References: Almodóvar J., Place L.W., Gogolski J., Kipper M.J.; “Layer-by-Layer Assembly of PolysaccharideBased Multilayers: A Spectroscopic Study of Hydrophilicity, Composition, and Ion Pairing”; Biomacromolecules, 12, 2011, 2755-2765
Funder Acknowledgement(s): Puerto Rico Louis Stroke Alliance for Minority Participation (PR-LSAMP) Undergraduate Research Scholarship - Institute for Functional Nanomaterials (IFN), Summer Undergraduate Internship - Department of Defense – Acquisition of Infrared Variable Angle Spectroscopic Ellipsometer - University of Puerto Rico – Mayaguez Campus.
Faculty Advisor: Jorge Almodovar-Montañez, email@example.com
Role: I mainly work with the IRVASE equipment. Once the samples are prepared, I run them in the IRVASE and analyze the data, observing chemical composition, variations due to temperature, thickness and optical constants. I also help prepare the samples in a way that would improve the data and results acquired from the equipment.