Synthesis of paclitaxel-loaded polycarbonate nanoparticles and hydrogels for improving oral bioavailability.

Introduction

Novel Drug Delivery Vehicles

Nanosponges: Preparation, Paclitaxel Encapsulation, &

Functionalization with PepT1-targeting peptide

Acknowledgements

References

Emily Douglas, David Stevens, Eva Harth* Department of Chemistry, Vanderbilt University, 7619 Stevenson Center, Nashville, TN 37235-1822

Department of Pharmaceutical Sciences, Lipscomb University College of Pharmacy, Nashville, TN 37204

Oral drug therapies face numerous obstacles before reaching the

systemic circulation and exerting their pharmacologic effects. Certain

drugs might survive the harsh gastrointestinal conditions; however, due to

their charge or low affinity for influx receptors in the intestine, they will not

be absorbed into the bloodstream. In order to improve the oral

bioavailability of such drugs, we investigate the potential of ‘nanosponges’

and hydrogels as delivery vehicles. We predict that these drug carriers will

shield their cargo from the drastic pH gradient in the gastrointestinal

system, slow enzymatic degradation, and enhance intestinal uptake. By

observing paclitaxel-loaded ‘nanosponges’ and hydrogels in pseudo-

gastric conditions in vitro, we can predict the stability of our drug carrier in

vivo. If successful, these vehicles could potentially serve as a novel oral

drug delivery systems.

1. Foley, D.; Pieri, M.; Pettecrew, R.; Price, R.; Miles, S.; Lam, H. K.; Bailey, P.; Meredith, D., The in vitro transport of model thiodipeptide prodrugs designed to target the intestinal oligopeptide transporter, PepT1. Organic & Biomolecular Chemistry 2009, 7 (18), 3652-3656. 2. Grover, G.; et. al. Biocompatible hydrogels by oxime click chemistry. Biomacromolecules, 2012, 13 (10), 3013 3017. 3. Stevens, D. M.; Tempelaar, S.; Dove, A. P.; Harth, E. Nanosponge Formation from Organocatalytically Synthesized Poly(carbonate) Copolymers. ACS Macro Letters 2012, 1(7), 915-918. 4. Truong, V.; et. al. Preparation of in situ-forming poly(5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one) poly(ethyleneglycol) hydrogels with tuneable swelling, mechanical strength and degradability. J. Mater. Chem. B, 2013, 1, 221.

Harth Lab: Principle Investigator - Eva Harth, PhD

Mentor – David Stevens, graduate

student

Vanderbilt Summer Science Academy

Lipscomb College of Pharmacy

Characteristics Nanosponge Hydrogel

Hydrolytically stable Yes Yes

Enzymatic degradation Slow Slow

Solubility (organics) Yes No

Solubility (water) Partially (PEG) No

Functionalization PepT1 targeting peptide None

[mon]:[ini

tiator]

Mn

(Predicte

d)

Mn (NMR)

(g/mol) PDI

Allyl %

incorporated

25 4,765 6,483 1.11 19.0

50 9,530 11,242 1.10 20.1

100 19,060 20,774 1.08 19.5

Time Points Amount

Degraded (g)

Control (3 hr) 0

30 min 0.0019

1 hr 0.0014

2 hr 0.0012

3 hr 0.0005

6 hr 0.0007

12 hr 0.0011

Variable pH throughout

GI tract

Enzymatic degradation

Intestinal absorption

barriers

First pass metabolism

Nanosponge Hydrogel

Linear polycarbonate precursor

Polycarbonate resists

significant degradation

in simulated gastric fluid

Hydrogels: Preparation & Paclitaxel

Encapsulation

1) Nanosponge Preparation

Amine/Epoxide Method:

R-OH

initiator MEC MAC

+ +

Sn(OTf)2

700C

(bulk)

3) Nanosponge Functionalization –

Targeting PepT1 Intestinal Transporter

m-CPBA

DCM

48 hrs

20%

10% DCM

450C, 12 hrs

500 nm

TEM reveals average

diameter of 500 nm

PTX + Water

VitE-TPGS

(DMSO)

1) Isobutyl chloroformate

N-methylmorpholine

2) AF647

DMSO

2) PTX-Encapsulation

via Nanosolubilization:

12% (w/w)

Low Polydispersity ~100mg of polycarbonate per sample

PTX

DMPA

DMSO

hv, 2 min

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10

Re

leas

ed

PTX

(%

)

Time (days)

PTX-Hydrogel Exhibits

Slow, Linear Release

Gels suspended in PBS buffer (pH 7.4) @ 370C

for a [PTX] of 0.15mM

Reverse phase HPLC using isocratic gradient ACN:H2O

(50:50)

Conclusions & Future Directions

We have successfully demonstrated the synthesis of two novel drug

delivery systems – nanosponges & hydrogels. In order to further test their

applicability as oral delivery vehicles, we will perform drug release studies

in pseudo-gastric conditions and analyze the intestinal uptake of our

PeptT1-targeted nanoparticles.