Multimodal Characterization of Resin Embedded and Sliced Polymer Nanoparticles by Means of Tip‐Enhanced Raman Spectroscopy and Force–Distance Curve Based Atomic Force Microscopy

Abstract

to their rich chemical and physical properties, which arise from the high variability of composition and morphologies. [1] As such organic, inorganic, and hybrid nanoparticles thereof find wide applications, in pharmaceutics, material design, such as coatings, cosmetics, optical and magnetics sensors, electronics, textiles, foods, or bioimaging. Most intriguing are nanoparticles exhibiting a core-shell structure with deviating electrical, magnetic, optical, chemical, catalytic, or thermal properties and high biocompatibility.Particularly, polymer nanoparticles, liposomes, polymersomes, polyplexes, and carbon based nanomaterials have attracted high attention for being used as drug carrier systems to treat diseases and disease-related complications. [2] Even more, amphiphilic polymers or block copolymers can self-assemble by means of nanoprecipitation, solvent exchange, emulsion, or dispersion polymerization, and other methods, [3] leading to a variety of different morphologies, including latex particles with distinct surface functionalities, core-shell structures, or even inner compartments. The determination of the surface properties and the internal structure of these nanoparticles is of high interest for understanding the property(structure)-function relation of such systems. [4] In Understanding the property-function relation of nanoparticles in various application fields involves determining their physicochemical properties, which is still a remaining challenge to date. While a multitude of different characterization tools can be applied, these methods by themselves can only provide an incomplete picture. Therefore, novel analytical techniques are required, which can address both chemical functionality and provide structural information at the same time with high spatial resolution. This is possible by using tipenhanced Raman spectroscopy (TERS), but due to its limited depth information, TERS is usually restricted to investigations of the nanoparticle surface. Here, TERS experiments are established on polystyrene nanoparticles (PS NPs) after resin embedding and microtome slicing. With that, unique access to their internal morphological features is gained, and thus, enables differentiation between information obtained for core-and shell-regions. Complementary information is obtained by means of transmission electron microscopy (TEM) and from force-distance curve based atomic force microscopy (FD-AFM). This multimodal approach achieves a high degree of discrimination between the resin and the polymers used for nanoparticle formulation. The high potential of TERS combined with advanced AFM spectroscopy tools to probe the mechanical properties is applied for quality control of the resin embedding procedure.

Nanoparticle Properties Influence Transendothelial Migration of Monocytes

“…Considering the range of particles assessed in this study, they can be divided broadly into three classes of particles: protein-based (pliable hydrogels with low elastic modulus), PMMA-based (jetted, amorphous polymer with moderate modulus and moderate pliability), and PS-based (semicrystalline polymer with high modulus and low pliability, very high negative surface charge). − Given that the Young’s modulus of SPNPs is in the range of 15–75 kPa (measured for ovalbumin), pliability of the nanoparticles included in this study trends as follows: SPNPs ≫ PMMA > PS. Considering this trend, it appears that lower modulus particles tend to reduce the overall migration of monocytes relative to stiffer particles.…”

Structural and Biochemical Changes in Pericardium upon Genipin Cross-Linking Investigated Using Nondestructive and Label-Free Imaging Techniques

“…On the other hand, scanning probe microscopy techniques, such as atomic force microscopy (AFM), provide superior resolution to conventional optical methods, and in fact, it has been used to monitor the D-spacing pattern in GA cross-linked pericardium, where changes in the D-spacing were observed during the formation of interfibrillar cross-links . Furthermore, Young’s modulus of collagen tissues can be estimated from AFM force–distance curves. , Hence, AFM could be used to investigate the nanostructure of GE cross-linked nanocomposites, where the surface images revealed highly compact structures. , In particular, multiparametric AFM investigations can ideally complement optical data to monitor environmental influences …”

Plasma modified and tailored defective electrocatalysts for water electrolysis and hydrogen fuel cells

“…186,187 For example, tip-enhanced Raman spectroscopy or photoluminescence spectroscopy combined with SEM convey the distribution of defects on the surfaces of the catalysts. 188,189 In addition, the geometric phase analysis (GPA) obtained by the combination of HR-TEM and lattice geometric parameter statistics discloses the geometric distribution of elements, phases, and defects. 190,191 Some surface characterization techniques such as sum frequency spectroscopy (SFG) and surface action spectroscopy combined with microscopic imaging play an important role in the in situ observation of the active site evolution of catalysts in real catalytic reactions.…”

“…The combination of spectroscopic and microscopic imaging can more effectively determine the structural defects in the electrocatalysts 186,187 . For example, tip‐enhanced Raman spectroscopy or photoluminescence spectroscopy combined with SEM convey the distribution of defects on the surfaces of the catalysts 188,189 . In addition, the geometric phase analysis (GPA) obtained by the combination of HR‐TEM and lattice geometric parameter statistics discloses the geometric distribution of elements, phases, and defects 190,191 …”