Thermodynamic and kinetic characterization of pH-dependent interactions between bovine serum albumin and ibuprofen in 2D and 3D systems

Surface Plasmon Resonance Imaging Sensor for Detection of Photolytically and Photocatalytically Degraded Glyphosate

Glyphosate is one of the most widely used pesticides, which, together with its primary metabolite aminomethylphosphonic acid, remains present in the environment. Many technologies have been developed to reduce glyphosate amounts in water. Among them, heterogeneous photocatalysis with titanium dioxide as a commonly used photocatalyst achieves high removal efficiency. Nevertheless, glyphosate is often converted to organic intermediates during its degradation. The detection of degraded glyphosate and emerging products is, therefore, an important element of research in terms of disposal methods. Attention is being paid to new sensors enabling the fast detection of glyphosate and its degradation products, which would allow the monitoring of its removal process in real time. The surface plasmon resonance imaging (SPRi) method is a promising technique for sensing emerging pollutants in water. The aim of this work was to design, create, and test an SPRi biosensor suitable for the detection of glyphosate during photolytic and photocatalytic experiments focused on its degradation. Cytochrome P450 and TiO₂ were selected as the detection molecules. We developed a sensor for the detection of the target molecules with a low molecular weight for monitoring the process of glyphosate degradation, which could be applied in a flow-through arrangement and thus detect changes taking place in real-time. We believe that SPRi sensing could be widely used in the study of xenobiotic removal from surface water or wastewater.

Tailoring Multifunctional Small Molecular Photosensitizers to In Vivo Self-Assemble with Albumin to Boost Tumor-Preferential Accumulation, NIR Imaging, and Photodynamic/Photothermal/Immunotherapy

Cancer immunotherapy has great potential in tumor eradication and metastasis suppression. However, systemic administration of immune adjuvants and inadequate specificity in cancer treatment, lead to restricted therapeutic benefits and potential immune-related side effects in clinical settings. In this report, the synthesis of various lengths of heptamethine cyanine small molecules to act as multifunctional photosensitizers (PS) for tumor-specific accumulation, near-infrared (NIR) fluorescent imaging, and photodynamic/photothermal/immunotherapy is optimized. In particular, it is demonstrated that C8, which contains eight carbons on two N-alkyl side chains, efficiently self-assembles with albumin to form nanosized dye-albumin complexes. This feature facilitates C8 in vivo self-assembly to remarkably improve its water-solubility, NIR fluorescent emission, long-term blood circulation, as well as tumor-specific accumulation. More importantly, C8 not only exhibits a superior phototherapeutic effect on primary tumors, but also elicits secretion of damage associated molecular patterns, cytokine secretion, dendritic cell maturation, and cytotoxic T lymphocytes activation, ultimately triggering a sufficient antitumor immune response to suppress growths of distant and metastatic tumors. Hence, this multifunctional small molecular PS is characterized with excellent tumor-preferential accumulation, imaging-guided laser irradiation, and phototherapy-induced in situ antitumor immune response, providing a prospective future of its use in tumor-targeting immunotherapy.

Interaction of Aqueous Bovine Serum Albumin with Silica Aerogel Microparticles: Sorption Induced Aggregation

Mesoporous silica aerogels have a wide range of potential applications in biotechnology, the food industry, pharmacy and medicine. Understanding the nature of the interactions of biomolecules with these porous nanostructured materials is essential for achieving optimum performance in the targeted applications. In this study, the well-characterized bovine serum albumin (BSA) was chosen as a model protein to probe protein–aerogel interactions in the solution phase. Aqueous BSA was mixed with suspended silica aerogel microparticles, and the colloid system was monitored on-line by UV–vis spectrophotometry and turbidimetry. The global mathematical analysis of the time-resolved data reveals that the fast sorption of the protein on the aerogel microparticles follows a multistep binding mechanism. The extensive sorption of the protein eventually induces the aggregation of the covered aerogel due to the alteration of the electrical double layer of the particles. The interaction of BSA and silica aerogel is the strongest between pH = 4 and 5, because their native surface charges are the opposite in this pH range, as indicated by their respective zeta potentials.

Evaluation of noble metal nanostructure-serum albumin interactions in 2D and 3D systems: Thermodynamics and possible mechanisms

In this review, we clearly highlight the importance of the detailed study of the interactions between noble metal colloids (nanoparticles (NPs) and nanoclusters (NCs)) with serum albumins (SAs) due to their rapidly growing presence in biomedical research. Besides the changes in the structure and optical property of SA, we demonstrate that the characteristic localized surface plasmon resonance (LSPR) feature of the colloidal noble metal NPs and the size- and structure-dependent photoluminescence (PL) property of the sub-nanometer sized NCs are also altered differently because of the interactions between them. Namely, for plasmonic NPs - SA interactions the PL quenching of SA (mainly static) is identified, while the SA cause PL enhancement of the ultra-small NCs after complexation. This review summarizes that the thermodynamic nature and the possible mechanisms of the binding processes are dependent partly on the size, morphology, and type of the noble metals, while the chemical structure as well as the charge of the stabilizing ligands have the most dominant effect on the change in optical features. In addition to the thermodynamic data and proposed binding mechanisms provided by three-dimensional spectroscopic techniques, the quantitative and real-time data of "quasi" two-dimensional sensor apparatus should also be considered to provide a comprehensive evaluation on many aspects of the particle/cluster - SA interactions.

The Theoretical Concept of Polarization Reflectometric Interference Spectroscopy (PRIFS): An Optical Method to Monitor Molecule Adsorption and Nanoparticle Adhesion on the Surface of Thin Films

In this paper, we present an improved reflectometric interference spectroscopy (RIfS) sensor principle which is suitable for thin films. The conventional RIfS technique is an appropriate method to detect interfacial interactions at the solid–gas or solid–liquid interface in the case of thin films with a thickness of a few hundred nanometers, but when a significantly lower layer thickness (~100 nm) is required, the method is barely usable. By applying polarized reflected light and monitoring the ratio of the p- and s-polarized components, a characteristic curve can be obtained with one or a few local extreme value(s) with significantly favorable intensity ratios compared to the conventional method. In this work we studied the effect of film thickness, incident angle and the refractive indices of the thin film, the medium and the substrate. As a main result, it was demonstrated that the sensitivity of the PRIfS method is 4–7 times higher than that of the conventional technique near a critical angle. In simulated adsorption experiments, it was determined that the sensitivity of RIfS is around 550 nm/RIU (refractive index unit), while it is 1825 and 3966 nm/RIU for PRIfS in gas and aqueous phase, respectively.

Applying Supercritical Fluid Technology to Prepare Ibuprofen Solid Dispersions with Improved Oral Bioavailability

In this study, supercritical fluid (SCF) technology was applied to prepare reliable solid dispersions of pharmaceutical compounds with limited bioavailability using ibuprofen (IBU) as a model compound. Solid-state characterization of the dispersions was conducted by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The PXRD and DSC results suggested that the amorphous form of IBU was maintained in the solid dispersions. Furthermore, in vitro dissolution and in vivo pharmacokinetic (PK) studies in rats were also performed. The dissolution performance of the SCF-prepared IBU dispersions was significantly improved compared to that of the physical mixtures of crystalline IBU and a polymer. In addition, the PK results revealed that the SCF-prepared IBU dispersions produced remarkably high blood drug concentrations (both the AUC and C_max) and a rapid absorption rate (T_max). Finally, molecular modeling was used to evaluate the binding energy of interactions between IBU and the polymers. The negative binding energy suggests a relatively stable system. Hence, SCF technology can be used as a very effective approach to prepare IBU solid dispersions with good physical stability and enhanced in vitro and in vivo performance.

Cross-linked and hydrophobized hyaluronic acid-based controlled drug release systems

This work demonstrates the preparation, structural characterization, and the kinetics of the drug release of hyaluronic acid (HyA)-based colloidal drug delivery systems which contain hydrophobic ketoprofen (KP) as model molecule. Because of the highly hydrophilic character of HyA the cross-linked derivatives at different cross-linking ratio have been synthesized. The hydrophobized variants of HyA have also been produced by modifying the polymer chains with cetyltrimethylammonium bromide (CTAB) at various HyA/CTAB ratios. Due to modifications the coherent structure of HyA changes into an incoherent colloidal system that were verified by rheological investigations. Nearly 70% of the encapsulated KP dissolve from the totally cross-linked HyA carrier but the release rate of KP is about 20% (after 8 h) from the CTAB-modified colloidal system at HyA monomer/CTAB 1:0.8 mass ratio. It has been verified that the modified HyA may be a potential candidate for controlled drug release of hydrophobic KP molecules.

Structure-Guided Design and Synthesis of a Mitochondria-Targeting Near-Infrared Fluorophore with Multimodal Therapeutic Activities

An urgent challenge for imaging-guided disease-targeted multimodal therapy is to develop the appropriate multifunctional agents to meet the requirements for potential applications. Here, a rigid cyclohexenyl substitution in the middle of a polymethine linker and two asymmetrical amphipathic N-alkyl side chains to indocyanine green (ICG) (the only FDA-approved NIR contrast agent) are introduced, and a new analog, IR-DBI, is developed with simultaneous cancer-cell mitochondrial targeting, NIR imaging, and chemo-/PDT/PTT/multimodal therapeutic activities. The asymmetrical and amphipathic structural modification renders IR-DBI a close binding to albumin protein site II to form a drug-protein complex and primarily facilitates its preferential accumulation at tumor sites via the enhanced permeability and retention (EPR) effect. The released IR-DBI dye is further actively taken up by cancer cells through organic-anion-transporting polypeptide transporters, and the lipophilic cationic property leads to its selective accumulation in the mitochondria of cancer cells. Finally, based on the high albumin-binding affinity, IR-DBI is modified into human serum albumin (HSA) via self-assembly to produce a nanosized complex, which exhibits significant improvement in the cancer targeting and multimodal cancer treatment with better biocompatibility. This finding may present a practicable strategy to develop small-molecule-based cancer theranostic agents for simultaneous cancer diagnostics and therapeutics.