Investigation of the Post-Synthetic Confinement of Fluorous Liquids Inside Mesoporous Silica Nanoparticles

Synthesis of Monodispersed Hollow Mesoporous Organosilica and Silica Nanoparticles with Controllable Shell Thickness Using Soft and Hard Templates

Hollow mesoporous nanoparticles with controllable size (less than 100 nm) are desired as drug-delivery carriers. Herein, we report the synthesis of monodispersed hollow mesoporous organosilica (HMOS) and hollow mesoporous silica (HMS) nanoparticles using soft and hard templating methods. HMOS shells, with 1,2-bis(triethoxysilyl)ethane (BTEE) as the precursor and hexadecyltrimethylammonium bromide and sodium dodecyl sulfate (SDS) as the soft templates, were formed on monodispersed silica nanoparticles (SNPs), which were used as the hard templates. HMOS and HMS nanoparticles were obtained by removing the SNPs after three rounds of ammonia dialysis. The hollow size of HMOS can be tuned by changing the size of the SNPs. By using SNPs with a size of 36.5 nm, hollow spaces of approximately 20 nm connected the surface through narrow pores (<5 nm). Mesopores of approximately 12 nm were formed by the surfactant micelles. Additionally, the interparticle space in HMOS and HMS was approximately 12 nm. The shell thicknesses of HMOS and HMS could be tuned in the range of 5-9 nm by changing the BTEE amount. Moreover, the amount of surfactant used varied the porous structure. The HMOS with a thickness of 5 nm exhibited a Brunauer-Emmett-Teller (BET) surface area of 268 m²/g and a total pore volume of 1.14 cm³/g. Meanwhile, HMS demonstrated a BET surface area of 553 m²/g and a total pore volume of 1.82 cm³/g while maintaining a hollow structure. HMOS displayed a high loading capacity for ibuprofen (3009 mg/g), and its drug release system showed a sustained-release property. Therefore, the HMOS preparation using hard and soft templates proposed herein can control the hollow size and shell thickness for drug-delivery applications.

Fluorous Liquids for Magnetic Resonance-Based Thermometry with Enhanced Responsiveness and Environmental Degradation

Accurate temperature measurement via magnetic resonance is valuable for both in vitro and in vivo analysis of local tissue for evaluating disease pathology and medical interventions. ¹H MRI-based thermometry is used clinically but is susceptible to error from magnetic field drift and low sensitivity in fatty tissue and requires a reference for absolute temperature determination. As an alternative, perfluorotributylamine (PFTBA), a perfluorocarbon liquid for ¹⁹F MRI thermometry, is based on chemical shift responsiveness and approaches the sensitivity of ¹H MRI thermometry agents; however, environmental persistence, greenhouse gas concerns, and multiple resonances which can lead to MRI artifacts indicate a need for alternative sensors. Using a ¹⁹F NMR-based structure-property study of synthetic organofluorine molecules, this research develops new organofluorine liquids with improved temperature responsiveness, high signal, and reduced nonmagnetically equivalent fluorine resonances. Environmental degradation analysis using reverse-phase HPLC and quantitative ¹⁹F NMR demonstrates a rapid degradation profile mediated via the aryl fluorine core of temperature sensors. Our findings show that our lead liquid temperature sensor, DD-1, can be made in high yield in a single step and possesses an improved responsiveness over our prior work and an 83% increase in aqueous thermal responsiveness over PFTBA. Degradation studies indicate robust degradation with half-lives of less than two hours under photolysis conditions for the parent compound and formation of other fluorinated products. The improved performance of DD-1 and its susceptibility to environmental degradation highlight a new lead fluorous liquid for thermometry applications.

Nanotechnology as a Versatile Tool for 19F-MRI Agent’s Formulation: A Glimpse into the Use of Perfluorinated and Fluorinated Compounds in Nanoparticles

Simultaneously being a non-radiative and non-invasive technique makes magnetic resonance imaging (MRI) one of the highly sought imaging techniques for the early diagnosis and treatment of diseases. Despite more than four decades of research on finding a suitable imaging agent from fluorine for clinical applications, it still lingers as a challenge to get the regulatory approval compared to its hydrogen counterpart. The pertinent hurdle is the simultaneous intrinsic hydrophobicity and lipophobicity of fluorine and its derivatives that make them insoluble in any liquids, strongly limiting their application in areas such as targeted delivery. A blossoming technique to circumvent the unfavorable physicochemical characteristics of perfluorocarbon compounds (PFCs) and guarantee a high local concentration of fluorine in the desired body part is to encapsulate them in nanosystems. In this review, we will be emphasizing different types of nanocarrier systems studied to encapsulate various PFCs and fluorinated compounds, headway to be applied as a contrast agent (CA) in fluorine-19 MRI (¹⁹F MRI). We would also scrutinize, especially from studies over the last decade, the different types of PFCs and their specific applications and limitations concerning the nanoparticle (NP) system used to encapsulate them. A critical evaluation for future opportunities would be speculated.