Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150745

150745 - Time-Separated Pulse Release-Activation of an Enzyme From Alginate-Based Hydrogel Using Electrochemically Produced Local Ph Changes 

In the last few decades, “smart” (bio)molecular release has been extensively studied due to its application for drug delivery. An appealing release stimuli is pH due to its endogenous nature often associated with the drug target destination. Electrochemistry allows to do local pH changes in a highly controlled manner via redox reactions of species naturally occurring in the human body.

In this work, electrochemically controlled cyclic local pH changes were used for pulsatile release of encapsulated β-glucosidase (EC 3.2.1.21) from alginate-polyethyleneimine hydrogel. β-glucosidase enzyme is used in the cancer therapy as well as considered as a component of an alternative to antibiotics. Its physical characteristics, such as molecular weight and charge, were very suitable to study its release from the composite hydrogel. In particular, propagation of basic pH towards the gel stimulated enzyme release (due to electrostatic repulsion), while propagation of acidic pH towards the gel inhibited the release (due to larger effect of electrostatic attraction). At the same time, the activity of this enzyme is pH-dependent being smaller at basic pH values. Thus, besides effect on the release, above-mentioned pH changes were used to inhibit or activate the enzyme activity in a cyclic manner. Moreover, one did not want the portion of the enzyme that was still encapsulated in the gel to be activated (helpful to prevent off-target associated toxicity), which was achieved by maintaining high pH in the carrier material. For that, polyethyleneimine (PEI) was used as a hydrogel component. PEI, being a polybase, was able to buffer the pH in the gel, so it stayed higher than the pH of the outside solution. PEI was also effective in the blocking of the acidic wave penetration into the gel. Positive charge created in the gel at this moment was beneficial for the retaining of still encapsulated β-glucosidase, which was negatively charged. Overall, propagation of the basic wave, while stimulating the release, was inhibiting the enzyme activity, while propagation of the acidic wave, while stopping the release, was activating only portion of the enzyme that was released to the solution. Thus, time-separated pulse release-activation of β-glucosidase from alginate-polyethyleneimine hydrogel using electrochemically generated local pH changes was achieved.

Both the release and activation of the enzyme were monitored through confocal fluorescence microscopy and fluorescence spectroscopy. In particular, non-fluorescence substrate (4-MUG) was hydrolyzed by β-glucosidase to produce highly fluorescent product (activity monitoring), while labeling of the enzyme with rhodamine B tag was used for the release observation.

Presenting Author: Ilya Sterin Clarkson University

Presenting Author Biography: Ilya Sterin received his M.Sc. in Chemical engineering from Politecnico di Milano (Milan, Italy) and M.Sc. in Biotechnology from MIREA – Russian technological university (Moscow, Russia) in 2020. In 2021 Ilya started his PhD study, joining research group of Prof. Katz and Prof. Melman in Clarkson University (Potsdam, NY, USA). His research interests are covering on-demand release systems from different materials, such as alginate hydrogels and metal organic frameworks

Authors:

Ilya Sterin Clarkson University
Anna Tverdokhlebova Clarkson University
Evgeny Katz Clarkson University
Oleh Smutok Clarkson University