Exploring tear viscosity with quartz crystal microbalance technology.

Tear viscosity is a critical property affecting tear distribution and ocular surface stability. While not widely established as a primary diagnostic marker, deviations from normal viscosity can impact ocular health, potentially contributing to conditions such as dry eye syndrome. Despite their importance, traditional viscometers require sample volumes that are not feasible to use with tear volume. This research introduces a novel Quartz Crystal Microbalance (QCM)-based method for tear viscosity measurement, offering a viscometer prototype that operates with minimal sample volumes. Human tear samples, solutions used in artificial eye drops, and various commercial eye drop brands were evaluated. Results show that the QCM method aligns with established viscosity ranges. The average viscosity of healthy human tears was found to be 1.73 ± 0.61 cP, aligning with the typical range of 1-10 cP. Variability in the viscosities of eye drop can be attributed to differences in their chemical compositions. The QCM method offers benefits such as reduced sample consumption and rapid results, enhancing understanding of tear dynamics for ocular health. Further research with larger sample sizes is needed to establish normative viscosity values in healthy individuals and those with dry eye syndrome, which is crucial for validating the device's clinical efficacy.

New Insights into Aptamers: An Alternative to Antibodies in the Detection of Molecular Biomarkers.

Aptamers are short oligonucleotides with single-stranded regions or peptides that recently started to transform the field of diagnostics. Their unique ability to bind to specific target molecules with high affinity and specificity is at least comparable to many traditional biorecognition elements. Aptamers are synthetically produced, with a compact size that facilitates deeper tissue penetration and improved cellular targeting. Furthermore, they can be easily modified with various labels or functional groups, tailoring them for diverse applications. Even more uniquely, aptamers can be regenerated after use, making aptasensors a cost-effective and sustainable alternative compared to disposable biosensors. This review delves into the inherent properties of aptamers that make them advantageous in established diagnostic methods. Furthermore, we will examine some of the limitations of aptamers, such as the need to engage in bioinformatics procedures in order to understand the relationship between the structure of the aptamer and its binding abilities. The objective is to develop a targeted design for specific targets. We analyse the process of aptamer selection and design by exploring the current landscape of aptamer utilisation across various industries. Here, we illuminate the potential advantages and applications of aptamers in a range of diagnostic techniques, with a specific focus on quartz crystal microbalance (QCM) aptasensors and their integration into the well-established ELISA method. This review serves as a comprehensive resource, summarising the latest knowledge and applications of aptamers, particularly highlighting their potential to revolutionise diagnostic approaches.

Deposition of Human-Serum-Albumin-Functionalized Spheroidal Particles on Abiotic Surfaces: Reference Kinetic Results for Bioparticles.

Human serum albumin (HSA) corona formation on polymer microparticles of a spheroidal shape was studied using dynamic light scattering and Laser Doppler Velocimetry (LDV). Physicochemical characteristics of the albumin comprising the zeta potential and the isoelectric point were determined as a function of pH for various ionic strengths. Analogous characteristics of the polymer particles were analyzed. The adsorption of albumin on the particles was in situ monitored by LDV. The stability of the HSA-functionalized particle suspensions under various pHs and their electrokinetic properties were also determined. The deposition kinetics of the particles on mica, silica and gold sensors were investigated by optical microscopy, AFM and quartz microbalance (QCM) under diffusion and flow conditions. The obtained results were interpreted in terms of the random sequential adsorption model that allowed to estimate the range of applicability of QCM for determining the deposition kinetics of viruses and bacteria at abiotic surfaces.

Monoolein-Based Wireless Capacitive Sensor for Probing Skin Hydration.

Capacitive humidity sensors typically consist of interdigitated electrodes coated with a dielectric layer sensitive to varying relative humidity levels. Previous studies have investigated different polymeric materials that exhibit changes in conductivity in response to water vapor to design capacitive humidity sensors. However, lipid films like monoolein have not yet been integrated with humidity sensors, nor has the potential use of capacitive sensors for skin hydration measurements been fully explored. This study explores the application of monoolein-coated wireless capacitive sensors for assessing relative humidity and skin hydration, utilizing the sensitive dielectric properties of the monoolein-water system. This sensitivity hinges on the water absorption and release from the surrounding environment. Tested across various humidity levels and temperatures, these novel double functional sensors feature interdigitated electrodes covered with monoolein and show promising potential for wireless detection of skin hydration. The water uptake and rheological behavior of monoolein in response to humidity were evaluated using a quartz crystal microbalance with dissipation monitoring. The findings from these experiments suggest that the capacitance of the system is primarily influenced by the amount of water in the monoolein system, with the lyotropic or physical state of monoolein playing a secondary role. A proof-of-principle demonstration compared the sensor's performance under varying conditions to that of other commercially available skin hydration meters, affirming its effectiveness, reliability, and commercial viability.

From adsorption to crystallization of proteins: Evidence for interface-assisted nucleation.

Protein crystallization is among the key processes in biomolecular research, but the underlying mechanisms are still elusive. Here, we address the role of inevitable interfaces for the nucleation process. Quartz crystal microbalance with dissipation monitoring (QCM-D) with simultaneously optical microscopy, confocal microscopy, and grazing-incidence small angle X-rays scattering (GISAXS) were employed to investigate the temporal behavior from the initial stage of protein adsorption to crystallization. Here we studied the crystallization of the Human Serum Albumin (HSA), the most abundant blood protein, in the presence of a charged surface and a trivalent salt. We found evidence for interface-assisted nucleation of crystals. The kinetic stages involved are initial adsorption followed by enhanced adsorption after longer times, subsequent nucleation, and finally crystal growth. The results highlight the importance of interfaces for protein phase behavior and in particular for nucleation.

Fragment-based approach to study fungicide-biomimetic membrane interactions.

In this study, the molecular interactions of the allylamine-type fungicide butenafine and a set of substructures ("fragments") with liposomes mimicking biological membranes were studied to gain a better understanding of the structural factors governing membrane affinity and perturbation. Specifically, drug/fragment-membrane interactions were investigated using an interdisciplinary approach involving micro differential scanning calorimetry, open-tubular capillary electrochromatography, nanoplasmonic sensing, and quartz crystal microbalance. By incubating the drug and the fragment compounds with liposomes with varying lipid composition or by externally adding the compounds to preformed liposomes, a detailed mechanistic picture on the underlying drug/fragment-membrane interactions was obtained. The nature and the degree of ionisation of polar head groups of the lipids had a major influence on the nature of drug-membrane interactions, and so had the presence and relative concentration of cholesterol within the membranes. The in-depth understanding of drug/fragment-membranes interactions established by the presented interdisciplinary fragment-based approach may be useful in guiding the design and early-stage evaluation of prospective antifungal drug candidates, and the discovery of agents with improved membrane penetrating characteristics in general.

Development of an Aptamer-Based QCM-D Biosensor for the Detection of Thrombin Using Supported Lipid Bilayers as Surface Functionalization.

Biosensors play an important role in numerous research fields. Quartz crystal microbalances with dissipation monitoring (QCM-Ds) are sensitive devices, and binding events can be observed in real-time. In combination with aptamers, they have great potential for selective and label-free detection of various targets. In this study, an alternative surface functionalization for a QCM-D-based aptasensor was developed, which mimics an artificial cell membrane and thus creates a physiologically close environment for the binding of the target to the sensor. Vesicle spreading was used to form a supported lipid bilayer (SLB) of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphethanolamine-N-(cap biotinyl) (biotin-PE). The SLB was then coated with streptavidin followed by applying a biotinylated aptamer against thrombin. SLB formation was investigated in terms of temperature and composition. Temperatures of 25 °C and below led to incomplete SLB formation, whereas a full bilayer was built at higher temperatures. We observed only a small influence of the content of biotinylated lipids in the mixture on the further binding of streptavidin. The functionalization of the sensor surface with the thrombin aptamer and the subsequent thrombin binding were investigated at different concentrations. The sensor could be reconstituted by incubation with a 5 M urea solution, which resulted in the release of the thrombin from the sensor surface. Thereafter, it was possible to rebind thrombin. Thrombin in spiked samples of human serum was successfully detected. The developed system can be easily applied to other target analytes using the desired aptamers.

[Microorganism Immobilization Device Using Artificial Siderophores].

Inspired by the mechanism by which microorganisms utilize siderophores to ingest iron, four different FeIII complexes of typical artificial siderophore ligands containing catecholate and/or hydroxamate groups, K3[FeIII-LC3], K2[FeIII-LC2H1], K[FeIII-LC1H2], and [FeIII-LH3], were prepared. They were modified on an Au substrate surface (Fe-L/Au) and applied as microorganism immobilization devices for fast, sensitive, selective detection of microorganisms, where H6LC3, H5LC2H1, H4LC1H2, and H3LH3 denote the tri-catecholate, biscatecholate-monohydroxamate, monocatecholate-bishydroxamate, and tri-hydroxamate type of artificial siderophores, respectively. Their adsorption properties for the several microorganisms were investigated using scanning electron microscopy (SEM), quartz crystal microbalance (QCM), and electric impedance spectroscopy (EIS) methods. The artificial siderophore-iron complexes modified on the Au substrates Fe-LC3/Au, Fe-LC2H1/Au, Fe-LC1H2/Au, and Fe-LH3/Au showed specific microorganism immobilization behavior with selectivity based on the structure of the artificial siderophores. Their specificities corresponded well with the structural characteristics of natural siderophores that microorganisms release from the cell and/or use to take up an iron. These findings suggest that release and uptake are achieved through specific interactions between the artificial siderophore-FeIII complexes and receptors on the cell surfaces of microorganisms. This study revealed that Fe-L/Au systems have specific potential to serve as effective immobilization probes of microorganisms for rapid, selective detection and identification of a variety of microorganisms.

Distance tuneable integral membrane protein containing floating bilayers via in situ directed self-assembly.

Model membranes allow for structural and biophysical studies on membrane biochemistry at the molecular level, albeit on systems of reduced complexity which can limit biological accuracy. Floating supported bilayers offer a means of producing planar lipid membrane models not adhered to a surface, which allows for improved accuracy compared to other model membranes. Here we communicate the incorporation of an integral membrane protein complex, the multidomain ß-barrel assembly machinery (Bam), into our recently developed in situ self-assembled floating supported bilayers. Using neutron reflectometry and quartz crystal microbalance measurements we show this sample system can be fabricated using a two-step self-assembly process. We then demonstrate the complexity of the model membrane and tuneability of the membrane-to-surface distance using changes in the salt concentration of the bulk solution. Results demonstrate an easily fabricated, biologically accurate and tuneable membrane assay system which can be utilized for studies on integral membrane proteins within their native lipid matrix.

A novel aptasensor platform for the detection of carcinoembryonic antigen using quartz crystal microbalance.

In this study, a quartz crystal microbalance (QCM) aptasensor for carcinoembryonic antigen (CEA), a well-known biomarker for various cancer types, was reported, utilizing two different aptamers. To achieve this, a nanofilm of 4-mercaptophenyl was electrochemically attached to gold-coated QCM crystal surfaces via the reduction of 4-mercaptobenzenediazonium salt (4 MB-DAT) using cyclic voltammetry. Subsequently, gold nanoparticles (AuNP) were affixed to this structure, and then aptamers (antiCEA1 and antiCEA2) modified with SH-functional ends bound to AuNPs completed the modification. The analytical performance of the CEA sensor was evaluated through simultaneous QCM measurements employing CEA solutions ranging from 0.1 ng/mL to 25 ng/mL. The detection limit (LOD) for CEA was determined to be 102 pg/mL for antiCEA1 and 108 pg/mL for antiCEA2 aptamers. Interday and intraday precision and accuracy tests yielded maximum results of 4.3 and + 3.8, respectively, for both aptasensors, as measured by relative standard deviation (RSD%) and relative error (RE%). The kinetic data of the aptasensors resulted in affinity values (KD) of 0.43 ± 0.14 nM for antiCEA1 and 0.75 ± 0.42 nM for antiCEA2. These values were lower than the reported values of 3.9 nM and 37.8 nM for both aptamers, respectively. The selectivity of the aptasensor was evaluated by measuring the signal changes caused by alpha-fetoprotein (AFP), cancer antigen (CA-125), and vascular endothelial growth factor (VEGF-165) individually and together at a concentration of 500 ng/mL, resulting in a maximum 4.1 % change, which was comparable to precision and accuracy values reported in the literature. After confirming the selectivity of the aptamers, recovery experiments were conducted using spiked commercial serum samples to simulate real samples, and the lowest recovery value obtained was 95.4 %. It was determined that two different aptasensors could be successfully used for the QCM-based detection of CEA in this study.

Real-time monitoring of dephosphorylation process of phosphopeptide and rapid assay of PTP1B activity based on a 100 MHz QCM biosensing platform.

The misregulation of protein phosphatases is a key factor in the development of many human diseases, notably cancers. Here, based on a 100 MHz quartz crystal microbalance (QCM) biosensing platform, the dephosphorylation process of phosphopeptide (P-peptide) caused by protein tyrosine phosphatase 1B (PTP1B) was monitored in real time for the first time and PTP1B activity was assayed rapidly and sensitively. The QCM chip, coated with a gold (Au) film, was used to immobilized thiol-labeled single-stranded 5'-phosphate-DNAs (P-DNA) through Au-S bond. The P-peptide, specific to PTP1B, was then connected to the P-DNA via chelation between Zr4+ and phosphate groups. When PTP1B was injected into the QCM flow cell where the P-peptide/Zr4+/MCH/P-DNA/Au chip was placed, the P-peptide was dephosphorylated and released from the Au chip surface, resulting in an increase in the frequency of the QCM Au chip. This allowed the real-time monitoring of the P-peptide dephosphorylation process and sensitive detection of PTP1B activity within 6 min with a linear detection range of 0.01-100 pM and a detection limit of 0.008 pM. In addition, the maximum inhibitory ratios of inhibitors were evaluated using this proposed 100 MHz QCM biosensor. The developed 100 MHz QCM biosensing platform shows immense potential for early diagnosis of diseases related to protein phosphatases and the development of drugs targeting protein phosphatases.

High-Frequency Quartz Crystal Microbalance and Dual-Signaling Electrochemical Ratiometric Assays of PTP1B Activity Based on COF@Au@Fc Hybrids.

The abnormal expression of protein tyrosine phosphatase 1B (PTP1B) is highly related to several serious human diseases. Therefore, an accurate PTP1B activity assay is beneficial to the diagnosis and treatment of these diseases. In this study, a dual-mode biosensing platform that enabled the sensitive and accurate assay of PTP1B activity was constructed based on the high-frequency (100 MHz) quartz crystal microbalance (QCM) and dual-signaling electrochemical (EC) ratiometric strategy. Covalent-organic framework@gold nanoparticles@ferrocene@single-strand DNA (COF@Au@Fc-S0) was introduced onto the QCM Au chip via the chelation between Zr4+ and phosphate groups (phosphate group of the phosphopeptide (P-peptide) on the QCM Au chip and the phosphate group of thiol-labeled single-stranded DNA (S0) on COF@Au@Fc-S0) and used as a signal reporter. When PTP1B was present, the dephosphorylation of the P-peptide led to the release of COF@Au@Fc-S0 from the QCM Au chip, resulting in an increase in the frequency of the QCM. Meanwhile, the released COF@Au@Fc-S0 hybridized with thiol/methylene blue (MB)-labeled hairpin DNA (S1-MB) on the Au NPs-modified indium-tin oxide (ITO) electrode. This caused MB to be far away from the electrode surface and Fc to be close to the electrode, leading to a decrease in the oxidation peak current of MB and an increase in the oxidation peak current of Fc. Thus, PTP1B-induced dephosphorylation of the P-peptide was monitored in real time by QCM, and PTP1B activity was detected sensitively and reliably using this innovative QCM-EC dual-mode sensing platform with an ultralow detection limit. This platform is anticipated to serve as a robust tool for the analysis of protein phosphatase activity and the discovery of drugs targeting protein phosphatase.

Effects of Carbon Spacer Length on Conformational Transitions and Protein Adsorption of Polyzwitterions.

The properties of polyzwitterions are closely linked to their carbon spacer length (CSL) between oppositely charged groups. A thorough understanding of the effect of CSL on the properties of polyzwitterion-functionalized membranes is important for their fouling resistance and separation performances. In this work, polyzwitterion-functionalized membranes with different CSLs are prepared by coupling selective swelling-induced pore generation with zwitterionization, and the investigation is focused on comprehending the molecular mechanisms underlying protein resistance and conformational transitions within polyzwitterions under varying CSLs. The zwitterionized films show an enhancement in the surface negative potential with the increase of CSL, attributed to the negatively charged groups distanced from the positively charged groups. Quartz crystal microbalance with dissipation (QCM-D) demonstrates that zwitterionized films with different CSLs display distinct levels of resistance to protein adsorption. The trimethylamine N-oxide-derived polymer (PTMAO, CSL = 0) zwitterionized film shows the highest resistance compared to the poly(3-[dimethyl(2'-methacryloyloxyethyl] ammonio) ethanesulfonate (PMAES, CSL = 2) zwitterionized film and the poly(sulfobetaine methacrylate) (PSBMA, CSL = 3) zwitterionized film, owing to its electrical neutrality and pronounced hydrophilicity. Moreover, analysis of the anti-polyelectrolyte behaviors reveals that PTMAO does not undergo a significant conformation transition in deionized water and salt solutions, while the conformations of PMAES and PSBMA display to be more salt-dependent as the CSL increases, attributed to their increased polarization and dipole moment. As a result, the permeability of zwitterionized membranes exhibits enhanced salt responsiveness with the increase in CSL. The findings of this study are expected to facilitate the design of adsorption-resistant surfaces desired in diverse fields.

Formation of sparsely tethered bilayer lipid membrane on a biodegradable self-assembled monolayer of poly(lactic acid).

The utilization of biomimetic membranes supported by advanced self-assembled monolayers is gaining attraction as a promising sensing tool. Biomimetic membranes offer exceptional biocompatibility and adsorption capacity upon degradation, transcending their role as mere research instruments to open new avenues in biosensing. This study focused on anchoring a sparsely tethered bilayer lipid membrane onto a self-assembled monolayer composed of a biodegradable polymer, functionalized with poly(ethylene glycol)-cholesterol moieties, for lipid membrane integration. Real-time monitoring via quartz crystal microbalance, coupled with characterization using surface-enhanced infrared absorption spectroscopy and electrochemical impedance spectroscopy, provided comprehensive insights into each manufacturing phase. The resulting lipid layer, along with transmembrane pores formed by gramicidin A, exhibited robust stability. Electrochemical impedance spectroscopy analysis confirmed membrane integrity, successful pore formation, and consistent channel density. Notably, gramicidin A demonstrated sustained functionality as an ion channel upon reconstitution, with its functionality being effectively blocked and inhibited in the presence of calcium ions. These findings mark significant strides in developing intricate biodegradable nanomaterials with promising applications in biomedicine.

Nanobubble transport in porous media: Towards agro- and environmental applications.

Nanobubbles have been increasingly used in various applications involving porous media, such as groundwater remediation and irrigation. However, the fundamental scientific knowledge regarding the interactions between nanobubbles and the media is still limited. The interactions can be repulsive, attractive, or inert, and can involve reversible or irreversible attachment as well as destructive mechanisms. Specifically, the stability and mobility of nanobubbles in porous media is expected to be dependent on the dynamic conditions and the physicochemical properties of the porous media, solutions, and nanobubbles themselves. In this study, we investigated how changes in solution chemistry (pH, ionic strength, and valence) and media characteristics (size and wettability) affect the size and concentration of nanobubbles under dynamic conditions using column experiments. Quartz crystal microbalance with dissipation monitoring provided a deeper understanding of irreversible and elastic nanobubbles' interactions with silica-coated surfaces. Our findings suggest that nanobubbles are less mobile in solutions of higher ionic strength and valence, acidic pH and smaller porous media sizes, while the wettability of porous media has a negligible influence on the retention of nanobubbles. Overall, our findings provide insights into the underlying mechanisms of nanobubble interactions and suggest potential strategies to optimize their delivery in various applications.

HIV and influenza fusion peptide interactions with (dis)ordered lipid bilayers: Understanding mechanisms and implications for antimicrobial and antiviral approaches.

The interactions of viral fusion peptides from influenza (E4K and Ac-E4K) and human immunodeficiency virus (gp41 and Ac-gp41) with planar lipid bilayers and monolayers was investigated herein. A combination of surface-sensitive techniques, including quartz crystal microbalance with dissipation (QCM-D), Langmuir-Blodgett area-pressure isotherms with Micro-Brewster angle microscopy, and neutron reflectometry, was employed. Differences in the interactions of the viral fusion peptides with lipid bilayers featuring ordered and disordered phases, as well as lipid rafts, were revealed. The HIV fusion peptide (gp41) exhibited strong binding to the DOPC/DOPS bilayer, comprising a liquid disordered phase, with neutron reflectometry (NR) showing interaction with the bilayer's headgroup area. Conversely, negligible binding was observed with lipid bilayers in a liquid ordered phase. Notably, the influenza peptide (E4K) demonstrated slower binding kinetics with DOPC/DOPS bilayers and distinct interactions compared to gp41, as observed through QCM-D. This suggests different mechanisms of interaction with the lipid bilayers: one peptide interacts more within the headgroup region, while the other is more involved in transmembrane interactions. These findings hold implications for understanding viral fusion mechanisms and developing antimicrobials and antivirals targeting membrane interactions. The differential binding behaviours of the viral fusion peptides underscore the importance of considering membrane composition and properties in therapeutic strategy design.

Acoustic detection of a mutation-specific Ligase Chain Reaction based on liposome amplification.

Single nucleotide variants (SNVs) play a crucial role in understanding genetic diseases, cancer development, and personalized medicine. However, existing ligase-based amplification and detection techniques, such as Rolling Circle Amplification and Ligase Detection Reaction, suffer from low efficiency and difficulties in product detection. To address these limitations, we propose a novel approach that combines Ligase Chain Reaction (LCR) with acoustic detection using highly dissipative liposomes. In our study, we are using LCR combined with biotin- and cholesterol-tagged primers to produce amplicons also modified at each end with a biotin and cholesterol molecule. We then apply the LCR mix without any purification directly on a neutravidin modified QCM device Au-surface, where the produced amplicons can bind specifically through the biotin end. To improve sensitivity, we finally introduce liposomes as signal enhancers. For demonstration, we used the detection of the BRAF V600E point mutation versus the wild-type allele, achieving an impressive detection limit of 220 aM of the mutant target in the presence of the same amount of the wild type. Finally, we combined the assay with a microfluidic fluidized bed DNA extraction technology, offering the potential for semi-automated detection of SNVs in patients' crude samples. Overall, our LCR/acoustic method outperforms other LCR-based approaches and surface ligation biosensing techniques in terms of detection efficiency and time. It effectively overcomes challenges related to DNA detection, making it applicable in diverse fields, including genetic disease and pathogen detection.

Combining QCM-D with live-cell imaging reveals the impact of serum proteins on the dynamics of fibroblast adhesion on tannic acid-functionalised surfaces.

Nanocoatings based on plant polyphenols have been recently suggested as a potent strategy for modification of implant surfaces for enhancing host cell attachment and reducing bacterial colonisation. In this study we aimed to investigate how serum proteins impact the early adhesion dynamics of human gingival fibroblasts onto titanium surfaces coated with tannic acid (TA). Silicate-TA nanocoatings were formed on titanium and pre-conditioned in medium supplemented with 0, 0.1, 1 or 10% FBS for 1 hour. Dynamics of fibroblasts adhesion was studied using quartz crystal microbalance with dissipation (QCM-D). Time-lapse imaging was employed to assess cell area and motility, while immunofluorescence microscopy was used to examine cell morphology and focal adhesion formation. Our results showed that in serum-free medium, fibroblasts demonstrated enhanced and faster adhesion to TA coatings compared to uncoated titanium. Increasing the serum concentration reduced cell adhesion to nanocoatings, resulting in nearly complete inhibition at 10% FBS. This inhibition was not observed for uncoated titanium at 10% FBS, although cell adhesion was delayed and progressed slower compared to serum-free conditions. In addition, 1% FBS dramatically reduced cell adhesion on uncoated titanium. We revealed a positive relationship between changes in dissipation and changes in cell spreading area, and a negative relationship between dissipation and cell motility. In conclusion, our study demonstrated that serum decreases fibroblasts interaction with surfaces coated with TA in a concentration dependent manner. This suggests that controlling serum concentration can be used to regulate or potentially prevent fibroblasts adhesion onto TA-coated titanium surfaces.

Structure Response of Preadsorbed Saliva Pellicle to the Interaction between Dairy and Saliva Protein.

Using the surface characterization techniques of quartz crystal microbalance with dissipation, atomic force microscopy, and scanning electron microscopy, the structure of the salivary pellicle was investigated before and after it was exposed to dairy proteins, including micellar casein, skim milk, whey protein isolate (WPI), and a mixture of skim milk and WPI. We have shown that the hydration, viscoelasticity, and adsorbed proteinaceous mass of a preadsorbed salivary pellicle on a PDMS surface are greatly affected by the type of dairy protein. After interaction with whey protein, the preadsorbed saliva pellicle becomes softer. However, exposure of the saliva pellicle to micellar casein causes the pellicle to partially collapse, which results in a thinner and more rigid surface layer. This structure change correlates with the measured lubrication behavior when the saliva pellicle is exposed to dairy proteins. While previous studies suggest that whey protein is the main component in milk to interact with salivary proteins, our study indicates interactions with casein are more important. The knowledge gained here provides insights into the mechanisms by which different components of dairy foods and beverages contribute to mouthfeel and texture perception, as well as influence oral hygiene.

Artificial protein coronas: directing nanoparticles to targets.

The protein corona surrounding nanoparticles (NPs) offers exciting possibilities for targeted drug delivery. However, realizing this potential requires direct evidence of corona-receptor interactions in vivo; a challenge hampered by the limitations of in vitro settings. This opinion proposes that utilizing engineered protein coronas can address this challenge. Artificial coronas made of selected plasma proteins retain their properties in vivo, enabling manipulation for specific receptor targeting. To directly assess corona-receptor interactions mimicking in vivo complexity, we propose testing artificial coronas with recently adapted quartz crystal microbalance (QCM) setups whose current limitations and potential advancements are critically discussed. Finally, the opinion proposes future experiments to decipher corona-receptor interactions and unlock the full potential of the protein corona for NP-based drug delivery.