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Methionine Functionalized Biocompatible Block Copolymers for Targeted Plasmid DNA Delivery
Published on: August 6, 2019
Release characteristics of a model plasmid DNA encapsulated in biodegradable poly(ethylene glycol
1Department of Bioengineering, Rice University, 6100 Main, Houston, TX 77005-1892, USA. jabbari.esmaiel@mayo.edu
Abstract:
Biodegradable hydrogel microspheres were synthesized by free radical suspension copolymerization of poly(ethylene glycol fumarate) macromer with bisacrylamide (PEGF/PAM). The acidic initiator ammonium persulphate in combination with the basic accelerator, N,N,N',N'-tetramethyethylenediamine, were used to form the PEGF/PAM hydrogel at a neutral pH. The equilibrium water content of the microspheres was greater than 90% w/w. A model double stranded plasmid DNA (dsDNA) coding for the enhanced green fluorescence protein (pEGFP) gene was encapsulated in the hydrogel and the effect of loading and water content before swelling on release kinetics was investigated. Fluorescent confocal microscopy demonstrated that the encapsulated dsDNA was in the biologically active double stranded configuration. The highest loading of 0.81 mg ml(-1) resulted in the best encapsulation efficiency of 95%. For that loading, 6% of the dsDNA was released in 25 days at a rate of 16 ng ml(-1). The highest water content of 70% resulted in the highest burst release of 27% and 14% of the dsDNA was released in 25 days at a rate of 30 ng ml(-1). For elucidating the release mechanism, the network mesh size was compared with the radius of gyration (Rg) of the dsDNA plasmid. The mesh size was 7 nm, which was less than Rg of the dsDNA (31 nm) but greater than the chain diameter of 1.1 nm. Since the mesh size was less than Rg, the release mechanism was by reptation of the segments of dsDNA within the tube formed by the network chains between crosslinks. These results indicate that the hydrogel mesh size and the size of the plasmid control the release mechanism.
Insights
Biodegradable hydrogel microspheres effectively encapsulate double-stranded DNA (dsDNA) for controlled release. The hydrogel
Area of Science:
- Biomaterials Science
- Polymer Chemistry
- Drug Delivery Systems
Background:
- Biodegradable hydrogels are promising for drug and gene delivery.
- Controlling the release kinetics of encapsulated biomolecules is crucial for therapeutic efficacy.
- Poly(ethylene glycol fumarate)/polyacrylamide (PEGF/PAM) hydrogels offer tunable properties.
Purpose of the Study:
- To synthesize biodegradable PEGF/PAM hydrogel microspheres.
- To encapsulate and investigate the release kinetics of double-stranded DNA (dsDNA).
- To elucidate the mechanism controlling dsDNA release from the hydrogel network.
Main Methods:
- Free radical suspension copolymerization of PEGF and bisacrylamide.
- Encapsulation of plasmid DNA (pEGFP) within hydrogel microspheres.
- Analysis of dsDNA release kinetics, encapsulation efficiency, and water content.
- Fluorescent confocal microscopy for dsDNA integrity assessment.
- Comparison of hydrogel mesh size with dsDNA radius of gyration (Rg) to determine release mechanism.
Main Results:
- PEGF/PAM hydrogel microspheres with >90% water content were synthesized.
- High encapsulation efficiency (95%) achieved at 0.81 mg/mL dsDNA loading.
- Controlled release observed: 6% dsDNA released over 25 days at 16 ng/mL.
- Higher water content led to increased burst release (27%) and faster overall release (30 ng/mL in 25 days).
- Hydrogel mesh size (7 nm) smaller than dsDNA Rg (31 nm) indicated reptation-controlled release.
Conclusions:
- PEGF/PAM hydrogel microspheres are suitable for encapsulating biologically active dsDNA.
- dsDNA release kinetics are significantly influenced by hydrogel water content and loading.
- The release mechanism is governed by the interplay between hydrogel mesh size and dsDNA dimensions, specifically reptation.
- These findings provide insights for designing hydrogel-based delivery systems for genetic material.
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