Supramolecular design of CO2-responsive lipid nanomaterials

Heterogeneous micellar solubilization within lyotropic liquid crystals interfaces

The solubilization of sodium diclofenac (Na-DFC) in a glycerol monooleate-based emulsion triggers series of structural changes. Incorporation of Na-DFC, leads to formation of a reverse hexagonal mesophase between 2 and 5 wt% Na-DFC. Between 6 and 9 wt% Na-DFC, the hexagonal symmetry gradually transitions to a disordered lamellar mesophase. These structural shifts impact the system's storage modulus, structuring enthalpy, and structural diffusivity. Despite these transitions, the driving force for Na-DFC release remains consistent, leading to hypothesize that the interfacial structure remains unchanged during Na-DFC release. The nano-structural modifications imposed by the Na-DFC load and release were assessed by small-angle X-ray diffraction (SAXD), spin-probe electron paramagnetic resonance (EPR), and nuclear quadrupole resonance (NQR). The selective solubilization of Na-DFC was demonstrated by SAXD peak fittings, revealing an increase of hexagonally oriented rods at the expense of non-oriented micelles, rather than gradual micellar elongation. Computation of the EPR spectra also showcased the selective solubilization of Na-DFC at an enhanced free energy interface (γ), evidenced by step-wise variations in polarity, microviscosity, and order parameters. Additionally, NQR analysis highlighted a higher anisotropy for sodium compared to deuterium, linking the selective solubilization of Na-DFC to heterogeneous structural transformations. These findings underscore the heterogeneous nature of solubilization-release processes, driven by locally increased micellar free energy. Consequently, the loaded Na-DFC interfaces maintain a constant γ, ensuring a consistent release driving force despite the structural transitions affecting the matrix. The ability to selectively solubilize guest molecules may herald a new era in the utilization of selective molecular interfacial loading.

CO2-Responsive Water-Soluble Conjugated Polymers as a Multifunctional Fluorescent Probe for Bioimaging Applications

We describe important progress in the synthesis and development of gas-responsive water-soluble conjugated polymers (WSCPs) with potential as multifunctional fluorescent materials for biomedical imaging and probes. A water-soluble WSCP (I-PT) composed of a hydrophobic fluorescent polythiophene backbone and a hydrophilic imidazole side chain was successfully prepared through a facile and efficient two-step synthetic route. Owing to the repulsive force between the hydrophilic and hydrophobic segments and the highly sensitive carbon dioxide (CO2)- and nitrogen (N2)-responsive imidazole groups in its structure, I-PT can spontaneously self-assemble into spherical-like nanoparticles in an aqueous environment, and thus exhibits unique light absorption and fluorescence properties as well as rapid responsiveness to CO2 and N2. In addition, its structure, optical absorption/fluorescence behavior, and surface potential can be quickly turned on and off through alternating cycles of CO2 and N2 bubbling and exhibit controllable cyclic switching stability, thereby allowing effective manipulation of its hierarchical structure and chemical-physical characteristics. More importantly, a series of in vitro cell experiments confirmed that, compared to the significant cytotoxicity of pristine and N2-treated I-PT nanoparticles, CO2-treated I-PT nanoparticles exhibit extremely low cytotoxicity in normal and cancer cells and undergo greatly accelerated cellular uptake, resulting in a significant increase in the intensity and stability of their fluorescence signal in the intracellular environment. Overall, this newly discovered CO2/N2-responsive system provides new insights to effectively enhance the biocompatibility, cellular internalization, and intracellular fluorescence characteristics of WSCPs and holds great potential for biomedical imaging/sensing applications.

Lipidic lyotropic liquid crystals: Insights on biomedical applications

Liquid crystals (LCs) possess unique physicochemical properties, translatable into a wide range of applications. To date, lipidic lyotropic LCs (LLCs) have been extensively explored in drug delivery and imaging owing to the capability to encapsulate and release payloads with different characteristics. The current landscape of lipidic LLCs in biomedical applications is provided in this review. Initially, the main properties, types, methods of fabrication and applications of LCs are showcased. Then, a comprehensive discussion of the main biomedical applications of lipidic LLCs accordingly to the application (drug and biomacromolecule delivery, tissue engineering and molecular imaging) and route of administration is examined. Further discussion of the main limitations and perspectives of lipidic LLCs in biomedical applications are also provided. STATEMENT OF SIGNIFICANCE: Liquid crystals (LCs) are those systems between a solid and liquid state that possess unique morphological and physicochemical properties, translatable into a wide range of biomedical applications. A short description of the properties of LCs, their types and manufacturing procedures is given to serve as a background to the topic. Then, the latest and most innovative research in the field of biomedicine is examined, specifically the areas of drug and biomacromolecule delivery, tissue engineering and molecular imaging. Finally, prospects of LCs in biomedicine are discussed to show future trends and perspectives that might be utilized. This article is an ampliation, improvement and actualization of our previous short forum article "Bringing lipidic lyotropic liquid crystal technology into biomedicine" published in TIPS.