(676g) Engineering pH Responsive, Self-Assembled Polymer Nanoparticles for the Oral Delivery of Protein Therapeutics

Engineering
pH Responsive, Self-assembled Polymer Nanoparticles for the Oral Delivery of Protein
Therapeutics

Matthew
K. Miller, Michael G. Elder, Lexi C. Lakatta,
and Nicholas A. Peppas

Introduction:
While protein therapeutics are promising treatment options in many realms of
disease, they are limited by their fragility. These therapeutics must be
delivered parenterally, which can lead to reduced patient compliance. An oral
delivery mechanism would be preferable; however, the conditions of the human
gastrointestinal tract are not amenable to naked protein delivery. Thus, this
work focuses on the development of a self-assembled, pH responsive nanoparticle
system capable of delivering antibodies orally comprised of block co-polymers
of methacrylic acid (MAA), methyl methacrylate (MMA), and PEG.

Methods:
A reversible deactivation radical polymerization scheme was used to synthesize poly(trimethylsilyl methacrylate-co-methyl methacrylate),
which was then conjugated to linear maleimide functionalized PEG10000 via
carbodiimide coupling chemistry. The trimethylsilyl groups were removed in mild
conditions to yield the final pH responsive di-block copolymer. Polymer
compositions and molecular weight were quantified by NMR and FTIR.
Nanoparticles were formed using a nanoprecipitation technique, and size and pH
mediated stability were analyzed via dynamic light scattering and nanoparticle
tracking analysis. Drug loading and release from the nanoparticles were analyzed
in vitro using the model protein IgG.
IgG concentrations were measured by ELISA.

Results:
The co-polymers exhibit a pH responsiveness mediated by the pKa
of MAA, which can be adjusted by co-polymerization with MMA. At a ratio of 1:1 MMA:MAA, the polymer exhibits a pKa
of approximately 6.0. This pKa allows the
nanoparticle to remain assembled throughout the stomach and upper small
intestine where the pH ranges from approximately pH 1-6. After passing through
the intestinal epithelium, the particle disassembles in the physiological pH
conditions found in the lamina propria, releasing its payload. In vitro drug release studies indicate
the particles release roughly 10-15% of their protein payload in pH 2.0 and pH
6.0 buffers, with near 100% release in pH 7.4 conditions. The formed
nanoparticles have a z-average diameter from 150-200nm with drug loading
efficiencies greater than 70% for polymer loaded in a 10 wt%
IgG solution. Future work will incorporate targeting moieties on the
nanoparticle surface via maleimide-thiol chemistry to facilitate
transepithelial transport.

Conclusions:
The block co-polymers synthesized in this work appear to be viable candidates
for the oral delivery of protein therapeutics. The self-assembled particles
protect the drug in the stomach and upper small intestine, while the higher pH
of the lamina propria leads to disassembly of the particle and release of the
therapeutics. Particle disassembly also facilitates more efficient release of
the payload compared to other delivery systems.

Acknowledgements:
This work was supported in part by the National Institutes of Health
(R01-EB-000246, R01-EB-022025) and the Cockrell Family Regents Chair. M.K.M. was also supported in part by a
National Science Foundation Graduate Research Fellowship (DGE-1610403), and the
Jodie Isenhower Endowed Graduate Fellowship in
Engineering.