pH-triggered shape response of cubical ultrathin hydrogel capsules

Abstract

We report on two types of poly(methacrylic acid) (PMAA)-based hydrogel microcontainers (capsules) of cubical shape with distinctly different shape responses upon pH variations. The microcontainers were prepared as replicas of cubical inorganic templates through chemical cross-linking of hydrogenbonded layer-by-layer (LbL) films. The two types of hollow hydrogels, a single-component (PMAA) and PMAA-poly(N-vinylpyrrolidone) (PMAA-PVPON), showed drastic differences in their shape response to pH variations. Cubical (PMAA) 20 capsules turned into bulged sphere-like structures of the same size when transitioned from pH 3 to pH 8. In contrast, cubical (PMAA-PVPON) 5 capsules retained their cubical shape at pH 3 while increasing in size at pH 8. The pH-triggered size change of cubical capsules was completely reversible. The difference in pH-triggered shape responses was rationalized through the difference in hydrogel rigidity expressed as the ratio of the polymer contour length between the neighboring cross-links to the persistence polymer length. The ratios of 22.7 and 2 for (PMAA) and (PMAA-PVPON) systems, respectively, suggested that the dual-component system is more rigid and therefore expands uniformly in all directions. We believe that the results provide new prospects for developing polymeric materials with predictable shape and size-changing properties for controlled drug delivery, cellular uptake, and pH-regulating transport behavior in microfluidic devices.

Internalization of Red Blood Cell-Mimicking Hydrogel Capsules with pH-Triggered Shape Responses

“…We found in our previous study that PMAA–PVPON cubical capsules can swell uniformly, expanding in size upon pH variations. 61 Unlike spheres and cubes, where length ( L ) and height ( H ) are similar, discoidal capsules studied here have a higher aspect ratio of L / H ≫1 (Figure 1a). In this aspect, the discoidal shape may be regarded as a derivative from the sphere with two circular faces of the initial sphere size, L , and the dramatically decreased height, H .…”

“…61 The molecular weights of PVPON-NH 2 -7 ( M w = 143 884 g mol –1 , M w / M n =1.55) and PMAA-NH 2 -5 ( M w = 130 000, M w / M n =1.50) were determined with GPC (Waters) using linear poly(vinylpyrrolidone) (American Polymer Standards Corp.) or polystyrene (Waters) standards, respectively.…”

Hydrogen‐Bonded Multilayers of Tannic Acid as Mediators of T‐Cell Immunity

“…[lxx,lxxi] Hydrogen-bonded multilayers of poly(methacrylic acid) with amino-containing poly(N-vinylpyrrolidone) (PVPON-NH 2 -7, M w = 143884 g mol −1 , Ð = 1.55) or poly(N-vinylcaprolactam) (PVCL-NH 2 −5, 23800, Ð = 1.5 ) copolymers with a certain molar percentage of amino group-containing polymer units were deposited on the silica particles. Assembly of the hydrogen-bonded layers was performed at pH=3.5, starting from PVPON-NH 2 or PVCL-NH 2 copolymer followed by PMAA.…”

Non-affinity factors modulating vascular targeting of nano- and microcarriers

“…Furthermore, an increasingly wide range of particle shapes has become available for biocompatible nanomaterials capable of drug delivery, with hydrogel capsules achieving cubic [66–68], discoidal [69,70], and hemispherical geometries [71] and hydrogel hemispheres and discs showing promise for uptake in macrophages, endothelial cells, and cancer cells [71,72]. Keeping in mind that carrier geometry affects practically every aspect of targeting – access, routing, binding, and uptake - more systematic, unified, and thorough studies of the role of geometry in targeting are necessary to guide carrier improvement and provide the data for computational analysis of this important subject.…”