Departmental webinar on "Self-assembly of similarly charged polyelectrolyte chains to form hierarchical structures" by Prof. Kamendra P Sharma, Department of Chemistry, IITB
20 Nov 2020
Department of Chemistry (online)
Departmental webinar on "Self-assembly of similarly charged polyelectrolyte chains to form hierarchical structures"
by Prof. Kamendra P Sharma, Department of Chemistry Indian Institute of Technology Bombay.
Time: Nov 20, 2020 04:00 PM
Talk Title : "Self-assembly of similarly charged polyelectrolyte chains to form hierarchical structures"
Abstract
In this lecture, I would speak about a specific cationic polymer,
Polyethyleneimine (PEI), well known for its gene transfection studies.
Generally, PEI is complexed with oppositely charged molecules to derive
polyplexes to be used for various drug delivery applications. The release
mechanism of these molecules from the polyplexes is highly dependent on
the pH of the surroundings. pH can modulate the charge and the
conformation of PEI chains leading to changes in its transfection
efficiency. The effect of pH on the polyplexes has not been well
understood, moreover, not even for pure PEI chains in aqueous solutions.
Our initial experimental observations suggest that at pH values between
2.5 to 4, neat PEI chains in explicit water undergo a completely
unprecedented and never observed before kind of self-assembly process. The
self-assembly is extremely slow, irreversible, and occurs under quiescent
conditions to form a 3-D fibrillar network comprising hollow fibrils. The
transition of ~ nm-sized PEI chains into micron-sized fibrillar network
follows coalescence of smaller PEI chains to form ~ 100-200 nm spheroidal
aggregates accompanied with conformational/ morphological transitions into
anisotropic rod-like aggregates which assemble end-to-end to form a
network structure. My lecture will mainly focus on our experimental
results; however, some PMF calculations based on MD simulations will also
be shown to support the experimental findings. We believe that our work
will initiate to seek more understanding in the gene delivery through
hyperbranched PEI-based polyplexes that occur under low pH conditions.