Disassembly of Nanospheres with a PEG Shell upon Adsorption onto PEGylated Substrates

Asymmetrical interactions between nanoparticles and proteins arising from deformation upon adsorption to surfaces

Drug release from polymeric nanoparticles (NPs) is governed by their adsorption onto cell membranes and transmigration across cell walls. These steps are influenced by their interactions with proteins near the cells. These interactions were investigated by studying the sequential adsorption of plasma proteins, albumin (Alb) and fibrinogen (Fg), and micellar NPs using quartz crystal microbalance with dissipation (QCMD), X-ray photoelectron spectroscopy (XPS), and small-angle X-ray scattering (SAXS). The three NPs in the study all have poly(ethylene glycol) (PEG) shells but different cores: amorphous poly(propylene oxide) (PPO), crystalline polycaprolactone (PCL), and poly(desaminotyrosyl-tyrosine octyl ester-co-suberic acid) (DTO-SA). None of the NPs adsorbed onto a pre-adsorbed Fg layer. On the other hand, when the deposition sequence was reversed, Fg was adsorbed onto DTO-SA NP and PCL NP surfaces, but not onto the PPO NP surface. The interactions with Alb were different: DTO-SA did not adsorb onto Alb and vice versa; PPO NP adsorbed onto an Alb layer, but Alb did not adsorb onto the PPO NP layer; and PCL NP reversibly adsorbed onto Alb, but Alb displaced pre-adsorbed PCL NP. Thus, in most instances, the adsorption behavior was asymmetric in that it was dependent on the order of arrival of the adsorbates at the substrate. SAXS data did not show evidence for complex formation in solution. Thus, the solution behavior appears not to be a predictor of the interaction of proteins and the NPs near surfaces. Differing strengths of pairwise interactions of proteins, NPs and substrates account for this adsorption behavior. These differences in interactions could be the results of deformation of the adsorbates immobilized at the surface and the different degrees of surface remodeling that occur upon adsorption. Deformation could lead to disassembly of the NPs that has implications on their ability to release their payload of drugs upon adsorption onto tissue surfaces.

Understanding the Adsorption and Desorption of Sitagliptin Phosphate Monohydrate on SS2343, Glass, and PTFE Using QCM-D and Raman Spectroscopy

Cross-contamination during pharmaceutical drug manufacturing can result in expensive recalls. To counter that, companies spend significant time and resources to ensure equipment cleanliness, often relying on the compound solubility data in various solvents as the main indicator of cleaning success. The aim of this work is to provide an alternative way to analyze the fouling and cleaning of surfaces in pharmaceutical manufacturing processes by using the quartz crystal microbalance with dissipation (QCM-D) and Raman spectroscopy. In this study, we chose an active pharmaceutical ingredient (API), sitagliptin phosphate monohydrate (SIT), as the model drug compound and observed its adsorption and desorption on stainless steel (SS2343), borosilicate glass (glass), and polytetrafluoroethylene (PTFE) surfaces. SIT was selected as the model API since it is a product manufactured on a large scale and is part of the widely used dipeptidyl peptidase-IV inhibitor class of oral hypoglycemics used to treat type 2 diabetes mellitus, while the chosen surfaces mimic the wall materials of manufacturing equipment and components such as reactors, transfer lines, and valves. Both the QCM-D and Raman spectroscopy results show the highest physisorption on PTFE, followed by SS2343 and glass. Additionally, QCM-D revealed a harder removal of SIT from SS2343 compared to glass and PTFE. Raman analysis of the chemical interactions disclosed C-F and C═O bond interactions between SIT and the surfaces, and the lack of a peak shift suggested dipole-dipole interactions. Furthermore, contact angle measurements indicate that hydrophobic attraction contributed to SIT adhesion to the PTFE surface. Subsequently, SIT coverage upon deposition on a PTFE surface has a significantly smaller surface area than on SS2343 and glass due to surface hydrophobicity, hence resulting in a longer removal time. These results provide a practical use of QCM-D and Raman spectroscopy to enhance the understanding of fouling and improve the cleaning of complex small molecules on relevant surfaces during the pharmaceutical manufacturing process.

Recent applications of QCM-D for the design, synthesis, and characterization of bioactive materials

The clinical translation of bioactive technologies is lacking compared to the number of novel technologies reported in the literature. This is in part due to the difficulties in characterizing bioactive materials to understand and predict their biological response. To progress the field and increase clinical success, more robust analytical techniques must be utilized when investigating novel bioactive materials. The quartz crystal microbalance with dissipation (QCM-D), a label-free sensing instrument based on an acoustic resonator, is used to quantify mass change and viscoelastic parameters from soft materials at the nanoscale, in situ, with precise temporal resolution and operation in both liquid and gaseous environments. The versatility of QCM-D has enhanced the characterization of bioactive polymers and sensing arrays for advanced applications of novel biotechnologies. In this review, we highlight exciting, recent applications of QCM-D for the investigation of bioactive materials. Attention is given to the dynamic mechanical properties of bioactive materials, discerning protein structure on surfaces, probing cell adhesion and cytoskeletal changes, and biosensing applications. We conclude that QCM-D has untapped utility in the pre-clinical investigation of bioactive materials and further utilization can improve the clinical success of novel technologies.