Stetson University

Betzaida Castillo-Cruz

Adjunct Professor of Chemistry

As a graduate student, Betzaida Castillo contributed to the mechanistic understanding of enzyme activity in organic solvents by using chemical modification of enzymes with poly(ethylene)glycol as a model system. Her thesis projects involved the chemical modification of proteases with poly(ethylene)glycol to understand the mechanism of enzyme activity and stability in organic solvents as well as the development of biophysical methods (employing chromatographic, kinetic and spectroscopic techniques) to study the function, structure, stability and conformational dynamics of proteases in organic solvents. As a postdoctoral research associate, she conducted biomedical research that focused on the stabilization and enhancement of the transfection efficiency of small interfering RNAs (siRNAs) by using delivery materials based on cationic polymers and polymer encapsulated magnetic particles. Since 2008, she has taught chemistry courses at the university level and is currently an adjunct professor in the chemistry department. 


  • Ph.D., chemistry, University of Puerto Rico, 2009
  • B.S., industrial chemistry, University of Puerto Rico, 2002

Course Topics

  • General Chemistry
  • Organic Chemistry 

Research Interests

  • Enzymology
  • Gene and drug delivery


  • Castillo, B., Bromberg, L., Lopez, X., Badillo, V., Gonzalez, J., Gonzalez, C., Hatton, T.A., and Barletta, G. (2012) "œIntracellular Delivery of siRNA by Polycationic Superparamagnetic Nanoparticles." Journal of Drug Delivery. 2012; 1-12.
  • Castillo, B., Delgado, Y., Barletta, G., and Griebenow, K. (2010) "Enantioselective Transesterification Catalysis by Nanosized Serine Protease Subtilisin Carlsberg Particles in Tetrahydrofuran." Tetrahedron. 66: 2175-2180.
  • Rodri­guez, J., Solii, R., Castillo, B., Cintron, H., Rivera, I., Barletta, G., and Griebenow, K. (2008) "œStabilization of Alpha- Chymotrypsin upon PEGylation Correlates with Reduced Structural Dynamics." Biotechnol. Bioeng. 101: 1142-1149.
  • Castillo, B., Solii, R., Ferrer, A., Barletta, G., and Griebenow, K. (2008) "€œEffect of PEG Modification on Subtilisin Carlsberg Activity, Enantioselectivity, and Structural Dynamics in 1,4 Dioxane." Biotechnol. Bioeng. 99: 9-17.
  • Castillo, B., Bansal, V., Ganesan, A., Halling P., Secundo F., Ferrer, A., Griebenow, K., Barletta, G. (2006) "€œOn the Activity Loss of Hydrolases in Organic Solvents: II. A Mechanistic Study of Subtilisin Carlsberg." BMC Biotechnol. 6: 51.
  • Fasoli, E., Castillo, B., Santos, A., Silva, E., Ferrer, A., Rosario, E., Griebenow, K., Secundo, F., and Barletta, G. (2006) "œActivation of Subtilisin Carlsberg in Organic Solvents by Methyl-Cyclodextrin: Lyoprotection vs Substrate and Product-Complex Effect." Journal of Molecular Catalysis B: Enzymatic. 42: 20-26.
  • Castillo, B., Mendez, J., Al-zzam, W., Barletta, G., and Griebenow, K. (2006) "œOn the Relationship Between the Activity and Structure of PEG-Chymotrypsin Conjugates in Organic Solvents." Biotechnol. Bioeng. 94: 565-574.
  • - Castillo, B., Pacheco, Y., Al-Azzam, W., Griebenow, K., Devi, M., Ferrer, A., Barletta, G. (2005) "€œOn the Activity Loss of Hydrolases in Organic Solvents. Rapid Loss of Activity of a Variety of Enzymes and Formulations in a Range of Organic Solvents." Journal of Molecular Catalysis B: Enzymatic 35: 147-153.

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