Multilayer DNA/poly(allylamine hydrochloride) microcapsules: assembly and mechanical properties

Area of Science:

• Materials Science
• Nanotechnology
• Biomaterials Engineering

Background:

• Layer-by-layer assembly is a versatile technique for creating functional thin films and microstructures.
• Understanding the mechanical properties of novel capsule materials is crucial for their application in drug delivery and diagnostics.

Purpose of the Study:

• To prepare and characterize DNA/poly(allylamine hydrochloride) (PAH) multilayer microcapsules.
• To investigate the mechanical properties of these novel microcapsules.
• To correlate the shell morphology and composition with the observed mechanical behavior.

Main Methods:

• Fabrication of DNA/PAH multilayers on planar supports and colloidal templates using layer-by-layer assembly.
• Characterization of film growth using Surface Plasmon Resonance (SPR) spectroscopy.
• Morphological analysis using Atomic Force Microscopy (AFM).
• Mechanical property assessment via AFM-based force-deformation measurements.

Main Results:

• Nonlinear growth of DNA/PAH multilayers observed, influenced by salt concentration and component concentrations.
• Distinct morphologies obtained based on the outermost layer: oriented DNA loops or highly porous PAH structures.
• DNA/PAH microcapsules exhibited lower stiffness (Young's modulus) compared to previously studied polyelectrolyte capsules.
• Post-treatment in salt solutions led to film thinning and an increase in the Young's modulus of the DNA/PAH shells.

Conclusions:

• DNA/PAH multilayer microcapsules can be successfully fabricated with tunable properties.
• The observed softening of DNA/PAH capsules is attributed to their higher permeability and lower Young's modulus.
• Post-treatment offers a method to enhance the mechanical integrity of DNA/PAH shells.