Synthesis and Characterization of Charged Hydrogels for the Extended Delivery of Vancomycin

Summary

Here we describe the synthesis and use of oligo(poly(ethylene glycol)fumarate) / sodium methacrylate (OPF/SMA) charged copolymers as an affinity based delivery system for vancomycin.

Abstract

Drug eluting polymers are of great interest due to their utility in cancer treatment, tissue regeneration, and infection prevention. It is desirable for these materials to offer tunable structural characteristics and molecular affinities, as well as excellent biocompatibility. In the context of surgery, infection of the wound site remains a significant risk for any procedure. It is standard practice to deliver systemic antimicrobial agents to combat infection of the surgical wound. To complement systemic therapy, an implantable, local delivery vehicle would be ideal. Our group investigated the utility of oligo(poly(ethylene glycol)fumarate) / sodium methacrylate (OPF/SMA) charged copolymers as a local delivery vehicle for the antimicrobial drug vancomycin. Here, we describe the methods of OPF synthesis, and OPF/SMA hydrogel production. Additionally, we demonstrate a facile chromatographic method for quantification of vancomycin loading and release from the OPF/SMA hydrogels. OPF-based biopolymers have proven to be biocompatible in vivo and have wide-ranging applications due to their ability to be crosslinked chemically or via ultra-violet irradiation. OPF is readily functionalized with charged groups, or mixed with other polymers to create co-polymers with optimal structural properties or unique responses to environmental stimuli. This study utilizes an array of charged OPF/SMA co-polymers to develop a controlled release vehicle for the broad spectrum antibiotic vancomycin based upon charge-charge interactions. Hydrogel loading of vancomycin can be quantified with a simple high performance liquid chromatography method. Vancomycin release from the hydrogels is initiated in the presence of free ions in solution, and release is buffered by free charges on the pendant chains within the crosslinked hydrogel. In sum, we report an efficient method for synthesis and characterization of the OPF/SMA hydrogels, and quantification of their ability to load and release vancomycin.

Introduction

Stimuli responsive hydrogels are of interest for their wide-ranging applications in enzyme / antibody immobilization, analytical techniques, nucleic acid and protein delivery, and cell encapsulation^{1,2,3,4,5,6,7}. Many such materials are polymer networks which contain charged pendant chains - thus electric field, temperature, pH, and ionic strength modulate the physical characteristics of the hydrogel. Thus, response to changes in physical....

Protocol

1. OPF/SMA hydrogel synthesis

1. Prepare the OPF macromer beginning with 10,000 Da poly(ethylene glycol) according to methods described by Kinard, et al.²¹.
2. Create a 10% w/v solution of photoinitiator by mixing with double-distilled water (ddH₂O). For example, add 100 mg of photoinitiator to 10 mL of ddH₂O. Add low heat (55 °C), and gently stir to dissolve completely.
3. In a 50 mL conical tube, mix the desired amount of 10,000.......

Discussion

The methods described here outline a facile method to synthesize OPF/SMA charged hydrogels, and to quantify the elution of a drug (vancomycin) from the hydrogel matrix. While the protocol is relatively straightforward, it may be useful to note several pitfalls which should be avoided during the synthesis, loading, and release in order to achieve more accurate results. During the hydrogel synthesis (see step 1.6), it is important to avoid the incorporation of air pockets in the co-polymer while pouring into a mold. This c.......

Materials

Name	Company	Catalog Number	Comments
Sodium methacrylate	Sigma	408212
Polyethylene glycol 10,000MW	Sigma	81280
50kDa exclusion dialysis tubing	Spectrum Labs	132129
1-Vinyl-2-pyrrolidinone	Sigma	95060
Irgacure 2959	BASF	106797-53-9
50mL Conical tubes	Corning	352098
Aluminum foil	Fisher Scientific	01-213-104
10cm dishes	Corning	353003
2mL low affinity microcentrifuge tubes	Fisher Scientific	02-681-321
Vancomycin hydrochloride	Sigma	V1130
Dulbecco's Phosphate Buffered Saline	Corning	21031
Thermogravimetric Analyzer	TA Instruments	TGA5500
1/8" thickness soda lime glass plate (1"x1")	Ace Hardware	11529
1/32" thickness white PTFE sheet	McMaster-Carr	8545K11