Fabrication and characterization of novel multilayered structures by stereocomplexion of poly(D-lactic acid)/poly(L-lactic acid) and self-assembly of polyelectrolytes

Abstract

SummaryThe enantiomers poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) were alternately adsorbed directly on calcium carbonate (CaCO3) templates and on poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) multilayer precursors in order to fabricate a novel layer-by-layer (LBL) assembly. A single layer of poly(L-lysine) (PLL) was used as a linker between the (PDLA/PLLA)n stereocomplex and the cores with and without the polymeric (PSS/PAH)n/PLL multilayer precursor (PEM). Nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) were used to characterize the chemical composition and molecular weight of poly(lactic acid) polymers. Both multilayer structures, with and without polymeric precursor, were firstly fabricated and characterized on planar supports. A quartz crystal microbalance (QCM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and ellipsometry were used to evaluate the thickness and mass of the multilayers. Then, hollow, spherical microcapsules were obtained by the removal of the CaCO3 sacrificial template. The chemical composition of the obtained microcapsules was confirmed by differential scanning calorimetry (DSC) and wide X-ray diffraction (WXRD) analyses. The microcapsule morphology was evaluated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements. The experimental results confirm the successful fabrication of this innovative system, and its full biocompatibility makes it worthy of further characterization as a promising drug carrier for sustained release.

Hollow Microcapsules with Enhanced Stability via Stereocomplex Assemblies

“…In contrast, a negligible change in the particles' diameter and cargo release was observed for the particles in acidic conditions, as shown in Figure S8 in the Supporting Information. This finding indicates that pH‐sensitivity and shedding of microcapsule shell derived from the supramolecular functionality, because PLA stereocomplexed microcapsules that had been prepared by the LbL technique and without functional groups were stable both in basic and acidic pH . The deprotonation of the UPy end‐groups induced a shrinking of the microcapsule under basic pH conditions .…”

“…This finding indicates that pH-sensitivity and shedding of microcapsule shell derived from the supramolecular functionality, [35] because PLA stereocomplexed microcapsules that had been prepared by the LbL technique and without functional groups were stable both in basic and acidic pH. [11] The deprotonation of the UPy endgroups induced a shrinking of the microcapsule under basic pH conditions. [23] Upon addition of the acid, the charge groups of the PLAs remained intact and the microcapsules' diameter did not change.…”

“…Inspired by this phenomenon, I hypothesized that the shell stability of stereocomplexed microcapsule can be greatly enhanced at the water–chloroform interface. To date, only the layer‐by‐layer (LbL) technique has been used to prepare stereocomplexed hollow nano‐ and microcapsules . However, this approach requires inorganic solid templates, multilayer precursors, and a linker between the stereocomplex and core .…”

“…To date, only the layer‐by‐layer (LbL) technique has been used to prepare stereocomplexed hollow nano‐ and microcapsules . However, this approach requires inorganic solid templates, multilayer precursors, and a linker between the stereocomplex and core . Additionally, this method uses harsh conditions to decompose the template material, which decreases the loading efficiency and often impairs the shell's integrity .…”

Tunable Interfacial Properties in Silk Ionomer Microcapsules with Tailored Multilayer Interactions

“…Biopolymers are an attractive class of candidate materials for this role as they typically interact with a host in a minimal way and are easily degraded through natural enzymatic processes . While some of these materials consist of simple biocompatible homopolymers (e.g., poly(lactic acid)), many complex biopolymers of interest are specific proteins, consisting of hundreds or thousands of precisely ordered residues, as opposed to most commonly used synthetic polymers, which consist of 1–2 repeat units arranged in a comparatively simple organization. Such complexity in the biopolymers can cause complex but weakly bound protein secondary and tertiary structures, leading to major changes in physical properties during fabrication into 3D morphologies, which can be challenging to predict a priori.…”