Cross-linker-Modulated Nanogel Flexibility Correlates with Tunable Targeting to a Sterically Impeded Endothelial Marker

Abstract

Deformability of injectable nanocarriers impacts rheological behavior, drug loading, and affinity target adhesion. Here, we present atomic force microscopy (AFM) and spectroscopy measurements of nanocarrier Young’s moduli, tune the moduli of deformable nanocarriers with cross-linkers, and demonstrate vascular targeting behavior that correlates with Young’s modulus. Homobifunctional cross-linkers were introduced into lysozyme-dextran nanogels (NGs). Single particle-scale AFM measurements determined NG moduli varying from ∼50–150 kPa for unmodified NGs or NGs with a short hydrophilic cross-linker (2,2′-(ethylenedioxy)­bis­(ethylamine), EOD) to ∼350 kPa for NGs modified with a longer hydrophilic cross-linker (4,9-dioxa-1,12-dodecanediamine, DODD) to ∼10 MPa for NGs modified with a longer hydrophobic cross-linker (1,12-diaminododecane, DAD). Cross-linked NGs were conjugated to antibodies for plasmalemma vesicle associated protein (PLVAP), a caveolar endothelial marker that cannot be accessed by rigid particles larger than ∼100 nm. In previous work, 150 nm NGs effectively targeted PLVAP, where rigid particles of similar diameter did not. EOD-modified NGs targeted PLVAP less effectively than unmodified NGs, but more effectively than DODD or DAD modified NGs, which both yielded low levels of targeting, resembling results previously obtained with polystyrene particles. Cross-linked NGs were also conjugated to antibodies against intracellular adhesion molecule-1 (ICAM-1), an endothelial marker accessible to large rigid particles. Cross-linked NGs and unmodified NGs targeted uniformly to ICAM-1. We thus demonstrate cross-linker modification of NGs, AFM determination of NG mechanical properties varying with cross-linker, and tuning of specific sterically constrained vascular targeting behavior in correlation with cross-linker-modified NG mechanical properties.

Biophysical Considerations in the Rational Design and Cellular Targeting of Flexible Polymeric Nanoparticles

“…2c). This observation agrees with those reported in earlier experimental studies 36 for in-vivo retention of ICAM-targeted flexible NPs in mouse lungs (inset of Fig. 2c and Supplementary Fig.…”

Biophysical Considerations in the Rational Design and Cellular Targeting of Flexible Polymeric Nanoparticles

“…Owing to competing enthalpic and entropic terms, there is no obvious systematic trend in how the total free energy of a flexible NP interacting with the cell membrane depends on the engineered changes in NP flexibility due to crosslinking (Figure 2c). This observation agrees with those reported in earlier experimental studies [36] on linking the flexibility of nanogels to the in vivo retention of ICAM-targeted nanogels in mouse lungs (Figure S2b, Supporting Information). It must be noted that the in vivo DAD crosslinker in Figure S2b (Supporting Information) represent a flexible NP with the highest crosslinking density.…”

Recent Advances in Nanocarrier-Assisted Therapeutics Delivery Systems

“…However, obstacles also exist for the clinical translation of nanogels. For example, when deformity occurs, their previously advantageous properties such as their swellability, drug loading capacity, and affinity target adhesion can be largely affected [67]. Constant efforts are also being made to optimize their biodistribution, to avoid their fast clearance, to minimize the toxicity caused by the surface charge, and to gain better control of targeted drug release and the degradation of nanogels [64,65].…”

“…Constant efforts are also being made to optimize their biodistribution, to avoid their fast clearance, to minimize the toxicity caused by the surface charge, and to gain better control of targeted drug release and the degradation of nanogels [64,65]. Working towards these goals, recently, Myerson et al developed a cross-linker modulated nanogel tunable in shape and equipped with antibodies specific to endothelial markers for improved targeted drug delivery [67].…”