SUNASEE RESEARCH LABORATORY
Associate Professor of Chemistry
SUNY Chancellor Award for Excellence in Teaching 2018
Plattsburgh Alumni Faculty Impact Award 2020
Councilor of the Northern New York ACS Local Section
Racial Equity & Justice Fellow
Equity Advocate
NANOCHEMISTRY RESEARCH
Research in the Sunasee laboratory focuses on the design, synthesis and characterization of modified cellulose nanocrystals for potential biomedical applications. Our initial progress so far in this area has been mainly on covalent surface functionalization of cellulose nanocrystals (CNCs) to introduce a cationic polymer, thermoresponsive polymer (pNIPAAm) and amino groups. Toxicity of modified CNCs is still at its infancy and our group in collaboration with Dr. Ckless's laboratory, look into detail the cytotoxicity and inflammatory activities of these modified CNCs. We are currently investigating the use of cationic CNCs as potential nanovaccine adjuvants (NSF-RUI funded project 2017-2021)
Cellulose Nanocrystals
Cellulose nanocrystals (CNCs) are biosourced non-toxic nanomaterials of great research interest in both academic and industrial sectors. These rigid rod-like cellulose crystals, obtained from the acidic hydrolysis of native cellulose, display remarkable strength and physicochemical properties with several potential applications.Their unique properties (nanoscale dimensions, biocompatibility, biodegradability, large surface area, low toxicity) and future commercialization prospects have recently led to the industrial production of CNCs in both USA and Canada. The ability to chemically modify CNCs through surface reactive hydroxyl groups opens up various potential applications, which is otherwise unachievable with unmodified CNCs. As a result, covalent or non-covalent chemical surface functionalization of CNCs continues to be an exciting area of research.
Cellulose nanocrystals decorated with amino groups
Our group recently disclosed a simple and mild two-step protocol for the synthesis of amine decorated CNCs. This method avoids the use of protecting groups, thereby, minimizing the number of steps required for the preparation of aminated CNCs. Both surface oxidation and amidation steps were confirmed spectroscopically. An improved yield for the amidation step (with respect to surface carboxylation) was observed. Elemental and XPS analysis also proved the covalent surface functionalization to be successful. An increase in zeta potential value of amine functionalized CNcs was observed as compared to unmodified CNCs. STEM images of the samples revealed that the structure and morphology of CNCs did not change after TEMPO oxidation, however, little agglomeration was observed upon surface covalent functionalization with diamines. The presence of terminal amino groups on the surface of CNCs represents a useful handle for further covalent conjugation with other biological moieties.
(Hemraz, U. D; Boluk, Y.; Sunasee, R.* “Amine-Decorated Nanocrystalline Cellulose Surfaces: Synthesis, Characterization and Surface Properties,” Can. J. Chem, 2013, 91, 974-981)
Poly(NIPAAm) grafted cellulose nanocrystals and their steric stability
In collaboration with Prof. Boluk's research group, thermo-responsive poly(N-isopropylacrylamide) (poly(NIPAAm)) brushes were grafted from the surface of cellulose nanocrystals (CNC) via living radical polymerization (LRP) using different initiator and monomer concentrations. The dry film thickness of the poly(NIPAAm) layer around CNC was calculated based on Scanning Electron Microscopy (SEM) and dynamic light scattering (DLS) measurements. The wet film thicknesses of grafted poly(NIPAAm) brushes in water were calculated to be 15 and 9 nm for NIPAAm-CNC-1 and NIPAAm-CNC-2, respectively. Grafted chain densities and wet film thicknesses at below and above the critical temperature (T=34 oC) of polyNIPAAm were calculated by applying mean-fieldanalytical theory. The non-ionic poly(NIPAAm) brushes screened the surface charges of CNC particles, leading to a significant decrease in the absolute zeta potential values for the poly(NIPAAm) grafted CNCs compared to the unmodified and initiator modified CNC samples. Nevertheless, the colloidal stability of poly(NIPAAm) grafted CNC particles were still maintained by steric stabilization below the critical temperature. On the other side, hydrophobic attractions among poly(NIPAAm) grafted CNC rods above 34 oC lead to coagulation and phase separation. While both poly(NIPAAm) grafted CNC samples showed thermo-responsive behavior, the reversibility of this temperature triggered property was dependent on grafting density.
(Hemraz, U. D.; Lu, A.; Sunasee, R.; Boluk, Y*. “Structure of poly(N-isopropylacrylamide) brushes and steric stability of their grafted cellulose nanocrystal dispersions,” Journal of Colloid and Interface Science, 2014, 430, 157-165).
Cellulose nanocrystals (CNCs) continue to gain increasing attention in the materials community as sustainable nanoparticles with unique chemical and mechanical properties. Their nanoscale dimensions, biocompatibility, biodegradability, large surface area and low toxicity make them promising materials for biomedical applications. Here, we disclose a facile synthesis of poly(2-aminoethylmethacrylate) (poly(AEM)) and poly(N-(2-aminoethylmethacrylamide) (poly(AEMA)) CNC brushes via surface-initiated single-electron transfer living radical polymerization technique. The resulting modified CNCs were characterized for their chemical and morphological features using a combination of analytical, spectroscopic and microscopic techniques. Zeta potential measurements indicated a positive surface charge and further proof of the cationic nature was confirmed by gold deposition as evidenced by electron microscopy. Cytotoxicity of these cationic modified CNCs was evaluated utilizing MTT assay in two different cell lines, J7734A1 (mouse monocyte cells) and MCF-7 (human breast adenocarcinoma cells). The results indicated that none of the cationic modified CNCs decreased cell viability at low concentrations, which are suitable for biomedical applications.
Hemraz, U.D.; Campbell, K.A.; Burdick, J.S.; Ckless, K.; Boluk, Y.; Sunasee, R.* “Cationic poly(2-aminoethylmethacrylate) and poly(N-(2-aminoethylmethacrylamide) modified cellulose nanocrystals: Synthesis, characterization and cytotoxicity,” Biomacromolecules, 2015, 16, 319-325).
