Green tea polyphenol tailors cell adhesivity of RGD displaying surfaces: multicomponent models monitored optically

Label-free biomolecular and cellular methods in small molecule epigallocatechin-gallate research

Small molecule natural compounds are gaining popularity in biomedicine due to their easy access to wide structural diversity and their proven health benefits in several case studies. Affinity measurements of small molecules below 100 Da molecular weight in a label-free and automatized manner using small amounts of samples have now become a possibility and reviewed in the present work. We also highlight novel label-free setups with excellent time resolution, which is important for kinetic measurements of biomolecules and living cells. We summarize how molecular-scale affinity data can be obtained from the in-depth analysis of cellular kinetic signals. Unlike traditional measurements, label-free biosensors have made such measurements possible, even without the isolation of specific cellular receptors of interest. Throughout this review, we consider epigallocatechin gallate (EGCG) as an exemplary compound. EGCG, a catechin found in green tea, is a well-established anti-inflammatory and anti-cancer agent. It has undergone extensive examination in numerous studies, which typically rely on fluorescent-based methods to explore its effects on both healthy and tumor cells. The summarized research topics range from molecular interactions with proteins and biological films to the kinetics of cellular adhesion and movement on novel biomimetic interfaces in the presence of EGCG. While the direct impact of small molecules on living cells and biomolecules is relatively well investigated in the literature using traditional biological measurements, this review also highlights the indirect influence of these molecules on the cells by modifying their nano-environment. Moreover, we underscore the significance of novel high-throughput label-free techniques in small molecular measurements, facilitating the investigation of both molecular-scale interactions and cellular processes in one single experiment. This advancement opens the door to exploring more complex multicomponent models that were previously beyond the reach of traditional assays.

Polysaccharide-based nano-engineered multilayers for controlled cellular adhesion in label-free biosensors

Controlling cellular adhesion is a critical step in the development of biomaterials, and in cell- based biosensing assays. Usually, the adhesivity of cells is tuned by an appropriate biocompatible layer. Here, synthetic poly(diallyldimethylammonium chloride) (PDADMAC), natural chitosan, and heparin (existing in an extracellular matrix) were selected to assembly PDADMAC/heparin and chitosan/heparin films. The physicochemical properties of macroion multilayers were determined by streaming potential measurements (SPM), quartz crystal microbalance (QCM-D), and optical waveguide lightmode spectroscopy (OWLS). The topography of the wet films was imaged using atomic force microscopy (AFM). The adhesion of preosteoblastic cell line MC3T3-E1 on those well-characterized polysaccharide-based multilayers was evaluated using a resonant waveguide grating (RWG) based optical biosensor and digital holographic microscopy. The latter method was engaged to investigate long-term cellular behavior on the fabricated multilayers. (PDADMAC/heparin) films were proved to be the most effective in inducing cellular adhesion. The cell attachment to chitosan/heparin-based multilayers was negligible. It was found that efficient adhesion of the cells occurs onto homogeneous and rigid multilayers (PDADMAC/heparin), whereas the macroion films forming "sponge-like" structures (chitosan/heparin) are less effective, and could be employed when reduced adhesion is needed. Polysaccharide-based multilayers can be considered versatile systems for medical applications. One can postulate that the presented results are relevant not only for modeling studies but also for applied research.

Glycocalyx Components Detune the Cellular Uptake of Gold Nanoparticles in a Size- and Charge-Dependent Manner

Functionalized nanoparticles (NPs) are widely used in targeted drug delivery and biomedical imaging due to their penetration into living cells. The outer coating of most cells is a sugar-rich layer of the cellular glycocalyx, presumably playing an important part in any uptake processes. However, the exact role of the cellular glycocalyx in NP uptake is still uncovered. Here, we in situ monitored the cellular uptake of gold NPs─functionalized with positively charged alkaline thiol (TMA)─into adhered cancer cells with or without preliminary glycocalyx digestion. Proteoglycan (PG) components of the glycocalyx were treated by the chondroitinase ABC enzyme. It acts on chondroitin 4-sulfate, chondroitin 6-sulfate, and dermatan sulfate and slowly on hyaluronate. The uptake measurements of HeLa cells were performed by applying a high-throughput label-free optical biosensor based on resonant waveguide gratings. The positively charged gold NPs were used with different sizes [d = 2.6, 4.2, and 7.0 nm, small (S), medium (M), and large(L), respectively]. Negatively charged citrate-capped tannic acid (CTA, d = 5.5 nm) NPs were also used in control experiments. Real-time biosensor data confirmed the cellular uptake of the functionalized NPs, which was visually proved by transmission electron microscopy. It was found that the enzymatic digestion facilitated the entry of the positively charged S- and M-sized NPs, being more pronounced for the M-sized. Other enzymes digesting different components of the glycocalyx were also employed, and the results were compared. Glycosaminoglycan digesting heparinase III treatment also increased, while glycoprotein and glycolipid modifying neuraminidase decreased the NP uptake by HeLa cells. This suggests that the sialic acid residues increase, while heparan sulfate decreases the uptake of positively charged NPs. Our results raise the hypothesis that cellular uptake of 2-4 nm positively charged NPs is facilitated by glycoprotein and glycolipid components of the glycocalyx but inhibited by PGs.

Free radical-scavenging composite gelatin methacryloyl hydrogels for cell encapsulation

Gelatin methacryloyl (GelMA) hydrogels have been widely used for cell encapsulation in tissue engineering due to their cell adhesiveness and biocompatibility. However, free radicals generated during gelation decrease the viability of the encapsulated cells by increasing intracellular oxidative stress, so appropriate strategies for scavenging free radicals need to be developed. To meet that need, we developed composite GelMA hydrogels incorporating nanofiber particles (EF) coated with epigallocatechin-gallate (EGCG). The GelMA composite hydrogels were successfully fabricated and had a storage modulus of about 5 kPa, which is similar to that of pristine GelMA hydrogel, and the drastic free radical scavenging activity of EGCG was highly preserved after gelation. In addition, human adipose-derived stem cells encapsulated within our composite hydrogels had better viability (about 1.5 times) and decreased intracellular oxidative stress (about 0.3 times) compared with cells within the pristine GelMA hydrogel. We obtained similar results with human dermal fibroblasts and human umbilical vein endothelial cells, indicating that our composite hydrogels are suitable for various cell types. Furthermore, we found that the ability of the encapsulated cells to spread and migrate increased by 5 times within the composite hydrogels. Collectively, our results demonstrate that incorporating EF into GelMA hydrogels is a promising way to enhance cell viability by reducing free-radical-derived cellular damage when fabricating 3D tissue ex vivo. STATEMENT OF SIGNIFICANCE: Gelatin methacryloyl (GelMA) hydrogels have been widely applied to various tissue engineering applications because of their biocompatibility and cell interactivity. However, free radicals generated during the GelMA hydrogel fabrication decrease the viability of encapsulated cells by elevating intracellular oxidative stress. Here, we demonstrate radical scavenging GelMA hydrogels incorporating epigallocatechin-gallate (EGCG)-coated nanofiber particles (EF). The composite GelMA hydrogels are successfully fabricated, maintaining their mechanical properties, and the viability of encapsulated human adipose-derived stem cells is greatly improved after the gelation, indicating that our composite GelMA hydrogel alleviates damages from free radicals. Collectively, the incorporation of EF within GelMA hydrogels may be a promising way to enhance the viability of encapsulated cells, which could be applied to 3D tissue fabrication.

Breathable, Moisturizing, Anti-Oxidation SSD-PG-PVA/KGM Fibrous Membranes for Accelerating Diabetic Wound Tissue Regeneration

Diabetic wound tissue repair and regeneration is a multi-step process that includes cell proliferation and migration, gas and moisture management, and inflammatory responses. However, current wound dressing designs lack consideration of the wound microenvironment of diabetic patients, making diabetic wound tissue repair a challenge. Here, we report a wound dressing (SSD-PG-PVA/KGM) with a porous structure and anti-oxidant properties for promoting diabetic wound tissue repair. First, the porous structure created by electrospinning technology encourages cell proliferation and migration in the wound while also providing breathability and moisture retention. Second, adding natural polyphenols (PG) and saikosaponins (SSDs) to the wound reduced reactive oxygen species levels and oxide stress. In vitro cell experiments showed that SSD-PG-PVA/KGM had good biocompatibility. Due to the biocompatibility, anti-oxidation ability, breathability, and moisturizing, SSD-PG-PVA/KGM could effectively promote the repair of diabetic wound tissue (the wound closure rate was 95.6% at 14 days).

Versatile polyphenolic platforms in regulating cell biology

Polyphenolic materials are a class of fascinating and versatile bioinspired materials for biointerfacial engineering. In particular, due to the presence of active chemical groups, a series of unique physicochemical properties become accessible and tunable of the as-prepared polyphenolic platforms, which could delicately regulate the cell activities via cell-material contact-dependent interactions. More interestingly, polyphenols could also affect the cell behaviors via cell-material contact-independent manner, which arise due to their intrinsically functional characteristics (e.g., antioxidant and photothermal behaviors). As such, a comprehensive understanding on the relationship between material properties and desired biomedical applications, as well as the underlying mechanism at the cellular and molecular level would provide material design principles and accelerate the lab-to-clinic translation of polyphenolic platforms. In this review, we firstly give a brief overview of cell hallmarks governed by surrounding cues, followed by the introduction of polyphenolic material engineering strategies. Subsequently, a detailed discussion on cell-polyphenols contact-dependent interfacial interaction and contact-independent interaction was also carefully provided. Lastly, their biomedical applications were elaborated. We believe that this review could provide guidances for the rational material design of multifunctional polyphenols and extend their application window.

Review of Label-Free Monitoring of Bacteria: From Challenging Practical Applications to Basic Research Perspectives

Novel biosensors already provide a fast way to detect the adhesion of whole bacteria (or parts of them), biofilm formation, and the effect of antibiotics. Moreover, the detection sensitivities of recent sensor technologies are large enough to investigate molecular-scale biological processes. Usually, these measurements can be performed in real time without using labeling. Despite these excellent capabilities summarized in the present work, the application of novel, label-free sensor technologies in basic biological research is still rare; the literature is dominated by heuristic work, mostly monitoring the presence and amount of a given analyte. The aims of this review are (i) to give an overview of the present status of label-free biosensors in bacteria monitoring, and (ii) to summarize potential novel directions with biological relevancies to initiate future development. Optical, mechanical, and electrical sensing technologies are all discussed with their detailed capabilities in bacteria monitoring. In order to review potential future applications of the outlined techniques in bacteria research, we summarize the most important kinetic processes relevant to the adhesion and survival of bacterial cells. These processes are potential targets of kinetic investigations employing modern label-free technologies in order to reveal new fundamental aspects. Resistance to antibacterials and to other antimicrobial agents, the most important biological mechanisms in bacterial adhesion and strategies to control adhesion, as well as bacteria-mammalian host cell interactions are all discussed with key relevancies to the future development and applications of biosensors.

Single-cell adhesivity distribution of glycocalyx digested cancer cells from high spatial resolution label-free biosensor measurements

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A high spatial resolution label-free biosensor monitors the adhesivity of cancer cells.

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Chondroitinase ABC was added to the adhering cells to digest their glycocalyx.

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Population level distributions of single-cell adhesivity were first recorded and analyzed.

At relatively low and high concentration subpopulations were identified.

The found subpopulations have remarkably large and weak adhesivities.

The glycocalyx is a cell surface sugar layer of most cell types that greatly influences the interaction of cells with their environment. Its components are glycolipids, glycoproteins, and oligosaccharides. Interestingly, cancer cells have a thicker glycocalyx layer compared to healthy cells, but to date, there has been no consensus in the literature on the exact role of cell surface polysaccharides and their derivatives in cellular adhesion and signaling. In our previous work we discovered that specific glycocalyx components of cancer cells regulate the kinetics and strength of adhesion on RGD (arginine-glycine-aspartic acid) peptide-coated surfaces [1]. Depending on the employed enzyme concentration digesting specific components both adhesion strengthening and weakening could be observed by monitoring the averaged behavior of thousands of cells. The enzyme chondroitinase ABC (ChrABC) was used to digest the chondroitin-4-sulfate, chondroitin-6-sulfate, and dermatan sulfate components in the glycocalyx of cancer cells. In the present work, a high spatial resolution label-free optical biosensor was employed to monitor the adhesivity of cancer cells both at the single-cell and population level. Population-level distributions of single-cell adhesivity were first recorded and analyzed when ChrABC was added to the adhering cells. At relatively low and high ChrABC concentrations subpopulations with remarkably large and weak adhesivity were identified. The changes in the adhesivity distribution due to the enzyme treatment were analyzed and the subpopulations most affected by the enzyme treatment were highlighted. The presented results open up new directions in glycocalyx related cell adhesion research and in the development of more meaningful targeted cancer treatments affecting adhesion.

Natural Compounds as Target Biomolecules in Cellular Adhesion and Migration: From Biomolecular Stimulation to Label-Free Discovery and Bioactivity-Based Isolation

Plants and fungi can be used for medical applications because of their accumulation of special bioactive metabolites. These substances might be beneficial to human health, exerting also anti-inflammatory and anticancer (antiproliferative) effects. We propose that they are mediated by influencing cellular adhesion and migration via various signaling pathways and by directly inactivating key cell adhesion surface receptor sites. The evidence for this proposition is reviewed (by summarizing the natural metabolites and their effects influencing cellular adhesion and migration), along with the classical measuring techniques used to gain such evidence. We systematize existing knowledge concerning the mechanisms of how natural metabolites affect adhesion and movement, and their role in gene expression as well. We conclude by highlighting the possibilities to screen natural compounds faster and more easily by applying new label-free methods, which also enable a far greater degree of quantification than the conventional methods used hitherto. We have systematically classified recent studies regarding the effects of natural compounds on cellular adhesion and movement, characterizing the active substances according to their organismal origin (plants, animals or fungi). Finally, we also summarize the results of recent studies and experiments on SARS-CoV-2 treatments by natural extracts affecting mainly the adhesion and entry of the virus.

Interfacing Live Cells with Surfaces: A Concurrent Control Technique for Quantifying Surface Ligand Activity

Surface ligand activity is a key design parameter for successfully interfacing surfaces with cells─whether in the context of in vitro investigations for understanding cellular signaling pathways or more applied applications in drug delivery and medical implants. Unlike other crucial surface parameters, such as stiffness and roughness, surface ligand activity is typically based on a set of assumptions rather than directly measured, giving rise to interpretations of cell adhesion that can vary with the assumptions made. To fill this void, we have developed a concurrent control technique for directly characterizing in vitro ligand surface activity. Pairs of gold-coated glass chips were biofunctionalized with RGD ligand in a parallel workflow: one chip for in vitro applications and the other for surface plasmon resonance (SPR)-based RGD activity characterization. Recombinant α_Vβ₃ integrins were injected over the SPR chip surface as mimics of the cellular-membrane-bound receptors and the resulting binding kinetics parameterized to quantify surface ligand activity. These activity measurements were correlated with cell morphological features, measured by interfacing MDA-MB-231 cells with the in vitro chip surfaces on the live cell microscope. We demonstrate how the interpretation of a cell phenotype based on direct activity measurements can vary markedly from interpretations based on assumed activity. The SPR concurrent control approach has multiple advantages due to the fact that SPR is a standardized technique and has the sensitivity to measure ligand activity across the most relevant range of extracellular surface densities, while the in vitro chip design can be used with all commonly used light microscopy modalities (e.g., phase contrast, DIC, and fluorescence) so that a wide range of phenotypic and molecular markers can be correlated to the ligand surface activity.

Single-cell adhesion strength and contact density drops in the M phase of cancer cells

The high throughput, cost effective and sensitive quantification of cell adhesion strength at the single-cell level is still a challenging task. The adhesion force between tissue cells and their environment is crucial in all multicellular organisms. Integrins transmit force between the intracellular cytoskeleton and the extracellular matrix. This force is not only a mechanical interaction but a way of signal transduction as well. For instance, adhesion-dependent cells switch to an apoptotic mode in the lack of adhesion forces. Adhesion of tumor cells is a potential therapeutic target, as it is actively modulated during tissue invasion and cell release to the bloodstream resulting in metastasis. We investigated the integrin-mediated adhesion between cancer cells and their RGD (Arg-Gly-Asp) motif displaying biomimetic substratum using the HeLa cell line transfected by the Fucci fluorescent cell cycle reporter construct. We employed a computer-controlled micropipette and a high spatial resolution label-free resonant waveguide grating-based optical sensor calibrated to adhesion force and energy at the single-cell level. We found that the overall adhesion strength of single cancer cells is approximately constant in all phases except the mitotic (M) phase with a significantly lower adhesion. Single-cell evanescent field based biosensor measurements revealed that at the mitotic phase the cell material mass per unit area inside the cell-substratum contact zone is significantly less, too. Importantly, the weaker mitotic adhesion is not simply a direct consequence of the measured smaller contact area. Our results highlight these differences in the mitotic reticular adhesions and confirm that cell adhesion is a promising target of selective cancer drugs as the vast majority of normal, differentiated tissue cells do not enter the M phase and do not divide.

Screening anti-metastasis drugs by cell adhesion-induced color change in a biochip

Metastasis is a frequent complication of cancer and accounts for more than 60% of patients' mortality. Despite technological advancements, treatment options are still limited. Ion channels participate in the regulation of cell adhesion, whilst the regulation of cell adhesion further controls metastasis formation. However, to develop a new ion channel inhibitor targeting metastasis takes tremendous effort and resources; therefore, drug repurposing is an emerging strategy in oncology. In previous studies, we have developed a metal-based nanoslit surface plasmon resonance (SPR) platform to examine the influence of drugs on the cell adhesion process. In this work, we developed a scanner-based cell adhesion kinetic examination (CAKE) system that is capable of monitoring the cell adhesion process by measuring color changes of SPR biosensors. The system's performance was demonstrated by screening the anti-metastasis ability of compounds from a commercial ion-channel inhibitor library. Out of the 274 compounds from the inhibitor library, zinc pyrithione (ZPT) and terfenadine were demonstrated to influence CL1-5 cell adhesion. The cell responses to the two compounds were then compared with those by traditional cell adhesion assays where similar behavior was observed. Further investigation of the two compounds using wound healing and transwell assays was performed and inhibitions of both cell migration and invasion by the two compounds were also observed. The results indicate that ZPT and terfenadine are potential candidates for anti-metastasis drugs. Our work has demonstrated the label-free drug screening ability of our CAKE system for finding potential drugs for cancer treatment.

Data evaluation for surface-sensitive label-free methods to obtain real-time kinetic and structural information of thin films: A practical review with related software packages

Interfacial layers are important in a wide range of applications in biomedicine, biosensing, analytical chemistry and the maritime industries. Given the growing number of applications, analysis of such layers and understanding their behavior is becoming crucial. Label-free surface sensitive methods are excellent for monitoring the formation kinetics, structure and its evolution of thin layers, even at the nanoscale. In this paper, we review existing and commercially available label-free techniques and demonstrate how the experimentally obtained data can be utilized to extract kinetic and structural information during and after formation, and any subsequent adsorption/desorption processes. We outline techniques, some traditional and some novel, based on the principles of optical and mechanical transduction. Our special focus is the current possibilities of combining label-free methods, which is a powerful approach to extend the range of detected and deduced parameters. We summarize the most important theoretical considerations for obtaining reliable information from measurements taking place in liquid environments and, hence, with layers in a hydrated state. A thorough treamtmaent of the various kinetic and structural quantities obtained from evaluation of the raw label-free data are provided. Such quantities include layer thickness, refractive index, optical anisotropy (and molecular orientation derived therefrom), degree of hydration, viscoelasticity, as well as association and dissociation rate constants and occupied area of subsequently adsorbed species. To demonstrate the effect of variations in model conditions on the observed data, simulations of kinetic curves at various model settings are also included. Based on our own extensive experience with optical waveguide lightmode spectroscopy (OWLS) and the quartz crystal microbalance (QCM), we have developed dedicated software packages for data analysis, which are made available to the scientific community alongside this paper.

A Review of Single-Cell Adhesion Force Kinetics and Applications

Cells exert, sense, and respond to the different physical forces through diverse mechanisms and translating them into biochemical signals. The adhesion of cells is crucial in various developmental functions, such as to maintain tissue morphogenesis and homeostasis and activate critical signaling pathways regulating survival, migration, gene expression, and differentiation. More importantly, any mutations of adhesion receptors can lead to developmental disorders and diseases. Thus, it is essential to understand the regulation of cell adhesion during development and its contribution to various conditions with the help of quantitative methods. The techniques involved in offering different functionalities such as surface imaging to detect forces present at the cell-matrix and deliver quantitative parameters will help characterize the changes for various diseases. Here, we have briefly reviewed single-cell mechanical properties for mechanotransduction studies using standard and recently developed techniques. This is used to functionalize from the measurement of cellular deformability to the quantification of the interaction forces generated by a cell and exerted on its surroundings at single-cell with attachment and detachment events. The adhesive force measurement for single-cell microorganisms and single-molecules is emphasized as well. This focused review should be useful in laying out experiments which would bring the method to a broader range of research in the future.

Green Tea Polyphenol-Sensitive Calcium Signaling in Immune T Cell Function

Polyphenol compounds found in green tea have a great therapeutic potential to influence multiple human diseases including malignancy and inflammation. In this mini review, we describe effects of green tea and the most important component EGCG in malignancy and inflammation. We focus on cellular mechanisms involved in the modification of T cell function by green tea polyphenol EGCG. The case is made that EGCG downregulates calcium channel activity by influencing miRNAs regulating expression of the channel at the post-transcriptional level.

Glycocalyx regulates the strength and kinetics of cancer cell adhesion revealed by biophysical models based on high resolution label-free optical data

The glycocalyx is thought to perform a potent, but not yet defined function in cellular adhesion and signaling. Since 95% of cancer cells have altered glycocalyx structure, this role can be especially important in cancer development and metastasis. The glycocalyx layer of cancer cells directly influences cancer progression, involving the complicated kinetic process of cellular adhesion at various levels. In the present work, we investigated the effect of enzymatic digestion of specific glycocalyx components on cancer cell adhesion to RGD (arginine-glycine-aspartic acid) peptide motif displaying surfaces. High resolution kinetic data of cell adhesion was recorded by the surface sensitive label-free resonant waveguide grating (RWG) biosensor, supported by fluorescent staining of the cells and cell surface charge measurements. We found that intense removal of chondroitin sulfate (CS) and dermatan sulfate chains by chondroitinase ABC reduced the speed and decreased the strength of adhesion of HeLa cells. In contrast, mild digestion of glycocalyx resulted in faster and stronger adhesion. Control experiments on a healthy and another cancer cell line were also conducted, and the discrepancies were analysed. We developed a biophysical model which was fitted to the kinetic data of HeLa cells. Our analysis suggests that the rate of integrin receptor transport to the adhesion zone and integrin-RGD binding is strongly influenced by the presence of glycocalyx components, but the integrin-RGD dissociation is not. Moreover, based on the kinetic data we calculated the dependence of the dissociation constant of integrin-RGD binding on the enzyme concentration. We also determined the dissociation constant using a 2D receptor binding model based on saturation level static data recorded at surfaces with tuned RGD densities. We analyzed the discrepancies of the kinetic and static dissociation constants, further illuminating the role of cancer cell glycocalyx during the adhesion process. Altogether, our experimental results and modelling demonstrated that the chondroitin sulfate and dermatan sulfate chains of glycocalyx have an important regulatory function during the cellular adhesion process, mainly controlling the kinetics of integrin transport and integrin assembly into mature adhesion sites. Our results potentially open the way for novel type of cancer treatments affecting these regulatory mechanisms of cellular glycocalyx.

Grating-coupled interferometry reveals binding kinetics and affinities of Ni ions to genetically engineered protein layers

Reliable measurement of the binding kinetics of low molecular weight analytes to their targets is still a challenging task. Often, the introduction of labels is simply impossible in such measurements, and the application of label-free methods is the only reliable choice. By measuring the binding kinetics of Ni(II) ions to genetically modified flagellin layers, we demonstrate that: (1) Grating-Coupled Interferometry (GCI) is well suited to resolve the binding of ions, even at very low protein immobilization levels; (2) it supplies high quality kinetic data from which the number and strength of available binding sites can be determined, and (3) the rate constants of the binding events can also be obtained with high accuracy. Experiments were performed using a flagellin variant incorporating the C-terminal domain of the nickel-responsive transcription factor NikR. GCI results were compared to affinity data from titration calorimetry. We found that besides the low-affinity binding sites characterized by a micromolar dissociation constant (Kd), tetrameric FliC-NikRC molecules possess high-affinity binding sites with Kd values in the nanomolar range. GCI enabled us to obtain real-time kinetic data for the specific binding of an analyte with molar mass as low as 59 Da, even at signals lower than 1 pg/mm2.

3D printed micro-chambers carrying stem cell spheroids and pro-proliferative growth factors for bone tissue regeneration

Three-dimensional (3D)-printed scaffolds have proved to be effective tools for delivering growth factors and cells in bone-tissue engineering. However, delivering spheroids that enhance cellular function remains challenging because the spheroids tend to suffer from low viability, which limits bone regenerationin vivo. Here, we describe a 3D-printed polycaprolactone micro-chamber that can deliver human adipose-derived stem cell spheroids. Anin vitroculture of cells from spheroids in the micro-chamber exhibited greater viability and proliferation compared with cells cultured without the chamber. We coated the surface of the chamber with 500 ng of platelet-derived growth factors (PDGF), and immobilized 50 ng of bone morphogenetic protein 2 (BMP-2) on fragmented fibers, which were incorporated within the spheroids as a new platform for a dual-growth-factor delivery system. The PDGF detached from the chamber within 8 h and the remains were retained on the surface of chamber while the BMP-2 was entrapped by the spheroid. In vitro osteogenic differentiation of the cells from the spheroids in the micro-chamber with dual growth factors enhanced alkaline phosphatase and collagen type 1A expression by factors of 126.7 ± 19.6 and 89.7 ± 0.3, respectively, compared with expression in a micro-chamber with no growth factors. In vivo transplantation of the chambers with dual growth factors into mouse calvarial defects resulted in a 77.0 ± 15.9% of regenerated bone area, while the chamber without growth factors and a defect-only group achieved 7.6 ± 3.9% and 5.0 ± 1.9% of regenerated bone areas, respectively. These findings indicate that a spheroid-loaded micro-chamber supplied with dual growth factors can serve as an effective protein-delivery platform that increases stem-cell functioning and bone regeneration.

Problem of Diminished cRGD Surface Activity and What Can Be Done about It

RGD peptides play a pivotal role in growing and diverse areas of biological research, ranging from in vitro experiments probing fundamental molecular mechanisms of cell adhesion to more applied in vivo strategies in medical imaging and cancer therapeutics. To better understand the outcomes of RGD-based approaches, we quantified the degree to which cyclic RGD (cRGD) activity is blocked by nonspecific binding of commonly used medium constituents. First, we show that recombinant α_Vβ₃ integrins can be used as a highly sensitive cell-free sensor to quantitatively and reliably characterize the activity of cRGD-functionalized surfaces via surface plasmon resonance (SPR). Next, SPR experiments were utilized to measure the extent of blocking of cRGD-functionalized surfaces by the commonly used agents BSA, PLL-g-PEG, and fetal calf serum (FCS)-supplemented media, using recombinant α_Vβ₃ integrin as a probe for cRGD binding activity in the presence of blocking agents. All three additives were highly efficient blockers of cRGD activity, as exemplified by cell culture media containing 1% FCS which reduced the cRGD activity by 33-fold. We then developed a strategy to combat these deleterious effects by employing the recombinant integrins as a protective cap. We show that the unblocked cRGD activity can be preserved in the presence of PLL-g-PEG by employing the α_Vβ₃ integrin as a removable protective cap, both in cell-free and in vitro experiments. In vitro studies with MDA-MB-231 cells cultured atop cRGD-functionalized surfaces found that cell adhesion and migration prevented by PLL-g-PEG were restored when this protective cap approach was used.

Human primary endothelial label-free biochip assay reveals unpredicted functions of plasma serine proteases

Tissue-on-a-chip technologies are more and more important in the investigation of cellular function and in the development of novel drugs by allowing the direct screening of substances on human cells. Constituting the inner lining of vessel walls, endothelial cells are the key players in various physiological processes, moreover, they are the first to be exposed to most drugs currently used. However, to date, there is still no appropriate technology for the label-free, real-time and high-throughput monitoring of endothelial function. To this end, we developed an optical biosensor-based endothelial label-free biochip (EnLaB) assay that meets all the above requirements. Using our EnLaB platform, we screened a set of plasma serine proteases as possible endothelial cell activators, and first identified the endothelial cell activating function of three important serine proteases - namely kallikrein, C1r and mannan-binding lectin-associated serine-protease 2 (MASP-2) - and verified these results in well-established functional assays. EnLaB proved to be an effective tool for revealing novel cellular mechanisms as well as for the high-throughput screening of various compounds on endothelial cells.

Single-cell adhesion force kinetics of cell populations from combined label-free optical biosensor and robotic fluidic force microscopy

Single-cell adhesion force plays a crucial role in biological sciences, however its in-depth investigation is hindered by the extremely low throughput and the lack of temporal resolution of present techniques. While atomic force microcopy (AFM) based methods are capable of directly measuring the detachment force values between individual cells and a substrate, their throughput is limited to few cells per day, and cannot provide the kinetic evaluation of the adhesion force over the timescale of several hours. In this study a high spatial and temporal resolution resonant waveguide grating based label-free optical biosensor was combined with robotic fluidic force microscopy to monitor the adhesion of living cancer cells. In contrast to traditional fluidic force microscopy methods with a manipulation range in the order of 300–400 micrometers, the robotic device employed here can address single cells over mm-cm scale areas. This feature significantly increased measurement throughput, and opened the way to combine the technology with the employed microplate-based, large area biosensor. After calibrating the biosensor signals with the direct force measuring technology on 30 individual cells, the kinetic evaluation of the adhesion force and energy of large cell populations was performed for the first time. We concluded that the distribution of the single-cell adhesion force and energy can be fitted by log-normal functions as cells are spreading on the surface and revealed the dynamic changes in these distributions. The present methodology opens the way for the quantitative assessment of the kinetics of single-cell adhesion force and energy with an unprecedented throughput and time resolution, in a completely non-invasive manner.

Oxidization increases the binding of EGCG to serum albumin revealed by kinetic data from label-free optical biosensor with reference channel

Schematic illustration of the biosensor to measure the EGCG–BSA interaction and the concentration dependent bound amount of EGCG and oxidized EGCG.

Epigallocatechin-3-Gallate Attenuates Microglial Inflammation and Neurotoxicity by Suppressing the Activation of Canonical and Noncanonical Inflammasome via TLR4/NF-κB Pathway

SCOPE

In this study, it has been investigated whether the neuroprotective efficacy of epigallocatechin-3-gallate (EGCG) is mediated by inhibition of canonical and noncanonical inflammasome activation via toll-like receptor 4 (TLR4)/NF-κB pathway both in LPS+Aβ-induced microglia in vitro and in APP/PS1 mice in vivo.

METHODS AND RESULTS

In BV2 cells, EGCG inhibits the expressions of Iba-1, cleaved IL-1β, and cleaved IL-18 induced by LPS+Aβ. Then, the supernatants are used to treat SH-SY5Y cells, and EGCG treatment significantly recovers the neurotoxicity from LPS+Aβ-induced microglial conditioned media. Subsequently, it has been found that EGCG reduces the microglial expressions of caspase-1 p20, NLRP3, and caspase-11 p26. Furthermore, the expression levels of Toll-like receptor 4 (TLR4), p-IKK/IKK, and p-NF-κB/NF-κB were decreased after EGCG treatment. As expected, when a caspase-1 specific inhibitor Z-YVAD-FMK, and an IKK and caspase-11 inhibitor wedelolactone are used for blocking, Z-YVAD-FMK and wedelolactone exacerbate the inhibitory efficacy than using EGCG alone. Finally, consistent with the results obtained in BV2 cells, EGCG treatment reduces microglial inflammation and neurotoxicity by suppressing the activation of canonical NLRP3 and noncanonical caspase-11-dependent inflammasome via TLR4/NF-κB pathway in LPS+Aβ-induced rat primary microglia and hippocampus of APP/PS1 mice.

CONCLUSION

EGCG attenuates microglial inflammation and neurotoxicity by inhibition of canonical NLRP3 and noncanonical caspase-11-dependent inflammasome activation via TLR4/NF-κB pathway.

A practical review on the measurement tools for cellular adhesion force

Cell-cell and cell-matrix adhesions are fundamental in all multicellular organisms. They play a key role in cellular growth, differentiation, pattern formation and migration. Cell-cell adhesion is substantial in the immune response, pathogen-host interactions, and tumor development. The success of tissue engineering and stem cell implantations strongly depends on the fine control of live cell adhesion on the surface of natural or biomimetic scaffolds. Therefore, the quantitative and precise measurement of the adhesion strength of living cells is critical, not only in basic research but in modern technologies, too. Several techniques have been developed or are under development to quantify cell adhesion. All of them have their pros and cons, which has to be carefully considered before the experiments and interpretation of the recorded data. Current review provides a guide to choose the appropriate technique to answer a specific biological question or to complete a biomedical test by measuring cell adhesion.

Biomimetic Dextran-Based Hydrogel Layers for Cell Micropatterning over Large Areas Using the FluidFM BOT Technology

Micropatterning of living single cells and cell clusters over millimeter-centimeter scale areas is of high demand in the development of cell-based biosensors. Micropatterning methodologies require both a suitable biomimetic support and a printing technology. In this work, we present the micropatterning of living mammalian cells on carboxymethyl dextran (CMD) hydrogel layers using the FluidFM BOT technology. In contrast to the ultrathin (few nanometers thick in the dry state) CMD films generally used in label-free biosensor applications, we developed CMD layers with thicknesses of several tens of nanometers in order to provide support for the controlled adhesion of living cells. The fabrication method and detailed characterization of the CMD layers are also described. The antifouling ability of the CMD surfaces is demonstrated by in situ optical waveguide lightmode spectroscopy measurements using serum modeling proteins with different electrostatic properties and molecular weights. Cell micropatterning on the CMD surface was obtained by printing cell adhesion mediating cRGDfK peptide molecules (cyclo(Arg-Gly-Asp-d-Phe-Lys)) directly from aqueous solution using microchanneled cantilevers with subsequent incubation of the printed surfaces in the living cell culture. Uniquely, we present cell patterns with different geometries (spot, line, and grid arrays) covering both micrometer and millimeter-centimeter scale areas. The adhered patterns were analyzed by phase contrast microscopy and the adhesion process on the patterns was real-time monitored by digital holographic microscopy, enabling to quantify the survival and migration of cells on the printed cRGDfK arrays.

Practical guide to characterize biomolecule adsorption on solid surfaces (Review)

The control over the adsorption or grafting of biomolecules from a liquid to a solid interface is of fundamental importance in different fields, such as drug delivery, pharmaceutics, diagnostics, and tissue engineering. It is thus important to understand and characterize how biomolecules interact with surfaces and to quantitatively measure parameters such as adsorbed amount, kinetics of adsorption and desorption, conformation of the adsorbed biomolecules, orientation, and aggregation state. A better understanding of these interfacial phenomena will help optimize the engineering of biofunctional surfaces, preserving the activity of biomolecules and avoiding unwanted side effects. The characterization of molecular adsorption on a solid surface requires the use of analytical techniques, which are able to detect very low quantities of material in a liquid environment without modifying the adsorption process during acquisition. In general, the combination of different techniques will give a more complete characterization of the layers adsorbed onto a substrate. In this review, the authors will introduce the context, then the different factors influencing the adsorption of biomolecules, as well as relevant parameters that characterize their adsorption. They review surface-sensitive techniques which are able to describe different properties of proteins and polymeric films on solid two-dimensional materials and compare these techniques in terms of sensitivity, penetration depth, ease of use, and ability to perform "parallel measurements."

Interaction of Positively Charged Gold Nanoparticles with Cancer Cells Monitored by an in Situ Label-Free Optical Biosensor and Transmission Electron Microscopy

Functionalized nanoparticles (NPs) can penetrate into living cells and vesicles, opening up an extensive range of novel directions. For example, NPs are intensively employed in targeted drug delivery and biomedical imaging. However, the real-time kinetics and dynamics of NP-living cell interactions remained uncovered. In this study, we in situ monitored the cellular uptake of gold NPs-functionalized with positively charged alkaline thiol-into surface-adhered cancer cells, by using a high-throughput label-free optical biosensor employing resonant waveguide gratings. The characteristic kinetic curves upon NP exposure of cell-coated biosensor surfaces were recorded and compared to the kinetics of NP adsorption onto bare sensor surfaces. We demonstrated that from the above kinetic information, one can conclude about the interactions between the living cells and the NPs. Real-time biosensor data suggested the cellular uptake of the functionalized NPs by an active process. It was found that positively charged particles penetrate into the cells more effectively than negatively charged control particles, and the optimal size for the cellular uptake of the positively charged particles is around 5 nm. These conclusions were obtained in a cost-effective, fast, and high-throughput manner. The fate of the NPs was further revealed by electron microscopy on NP-exposed and subsequently fixed cells, well confirming the results obtained by the biosensor. Moreover, an ultrastructural study demonstrated the involvement of the endosomal-lysosomal system in the uptake of functionalized NPs and suggested the type of the internalization pathway.

Polyphenols, food and pharma. Current knowledge and directions for future research

Polyphenols are a large family of phytochemicals with great chemical diversity, known to be bioactive compounds of foods, species, medicinal plants and nutraceuticals. These compounds are ingested through the diet in significant amounts, around 1 g per day, an amount that be may be increased through supplements. The in vitro action of many representative polyphenols has been reported. However, their beneficial effects and their role in modulating the risk of high-prevalence diseases are difficult to demonstrate due to the wide variability of polyphenol structures and bioactive actions; the complexity of estimating the polyphenol content of food as a result of their variability in foods and cooked dishes; the potential modulation of the effects of polyphenols by food matrices; the addition of polyphenols and their synergistic interactions with each other and with other dietary bioactive components; the modulation of polyphenol bioavailability as a consequence of food composition and culinary techniques; their metabolism by the human body and the polyphenol gut microbiota metabolism in each metabotypes. Computational strategies, including virtual screening, shape-similarity-screening and molecular docking, were recently used to identify potential targets of polyphenols and thus gain a better understanding of the therapeutic effects exerted of polyphenols and modify natural polyphenol structures to potentiate specific activities. Here, we present the most relevant current knowledge and propose directions for future research in these fields, from the culinary world to the clinical setting. We hope this commentary will prompt scientists and clinicians to consider the therapeutic value of bioactive polyphenols and help shed some light on how much scientific truth lies in Hippocrates' famous quote: "Let your food be your medicine".

Label-free optical biosensor for real-time monitoring the cytotoxicity of xenobiotics: A proof of principle study on glyphosate

Rapid and inexpensive biosensor technologies allowing real-time analysis of biomolecular and cellular events have become the basis of next-generation cell-based screening techniques. Our work opens up novel opportunities in the application of the high-throughput label-free Epic BenchTop optical biosensor in cell toxicity studies. The Epic technology records integrated cellular responses about changes in cell morphology and dynamic mass redistribution of cellular contents at the 100-150 nm layer above the sensor surface. The aim of the present study was to apply this novel technology to identify the effect of the herbicide Roundup Classic, its co-formulant polyethoxylated tallow amine (POEA), and its active ingredient glyphosate, on MC3T3-E1 cells adhered on the biosensor surface. The half maximal inhibitory concentrations of Roundup Classic, POEA and glyphosate upon 1 h of exposure were found to be 0.024%, 0.021% and 0.163% in serum-containing medium and 0.028%, 0.019% and 0.538% in serum-free conditions, respectively (at concentrations equivalent to the diluted Roundup solution). These results showed a good correlation with parallel end-point assays, demonstrating the outstanding utility of the Epic technique in cytotoxicity screening, allowing not only high-throughput, real-time detection, but also reduced assay run time and cytotoxicity assessment at end-points far before cell death would occur.

High-Resolution Adhesion Kinetics of EGCG-Exposed Tumor Cells on Biomimetic Interfaces: Comparative Monitoring of Cell Viability Using Label-Free Biosensor and Classic End-Point Assays

A high-throughput label-free resonant waveguide grating biosensor, the Epic BenchTop, was utilized to in situ monitor the adhesion process of cancer cells on Arg-Gly-Asp tripeptide displaying biomimetic polymer surfaces. Using highly adherent human cervical adenocarcinoma (HeLa) cells as a model system, cell adhesion kinetic data with outstanding temporal resolution were obtained. We found that pre-exposing the cells to various concentrations of the main extract of green tea, the (-)-epigallocatechin gallate (EGCG), largely affected the temporal evolution of the adhesion process. For unexposed and low dosed cells, sigmoid shaped spreading kinetics was recorded. Higher dose of EGCG resulted in a complete absence of the sigmoidal character, and displayed adsorption-like kinetics. By using the first derivatives of the kinetic curves, a simple model was developed to quantify the sigmoidal character and the transition from sigmoidal to adsorption-like kinetics. The calculations showed that the transition happened at EGCG concentration of around 60 μg/mL. Using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide end-point assay, we concluded that EGCG is cytostatic but not cytotoxic. The effect of EGCG was also characterized by flow cytometry. We concluded that, using the introduced label-free methodology, the shape of the cell adhesion kinetic curves can be used to quantify in vitro cell viability in a fast, cost-effective, and highly sensitive manner.

Experimental Study of the Oriented Immobilization of Antibodies on Photonic Sensing Structures by Using Protein A as an Intermediate Layer

A proper antibody immobilization on a biosensor is a crucial step in order to obtain a high sensitivity to be able to detect low target analyte concentrations. In this paper, we present an experimental study of the immobilization process of antibodies as bioreceptors on a photonic ring resonator sensor. A protein A intermediate layer was created on the sensor surface in order to obtain an oriented immobilization of the antibodies, which enhances the interaction with the target antigens to be detected. The anti-bovine serum albumin (antiBSA)-bovine serum albumin (BSA) pair was used as a model for our study. An opto-fluidic setup was developed in order to flow the different reagents and, simultaneously, to monitor in real-time the spectral response of the photonic sensing structure. The antiBSA immobilization and the BSA detection, their repeatability, and specificity were studied in different conditions of the sensor surface. Finally, an experimental limit of detection for BSA recognition of only 1 ng/mL was obtained.

In vitro study on anti-inflammatory effects of epigallocatechin-3-gallate-loaded nano- and microscale particles

Purpose

This study aimed to develop an anti-inflammation system consisting of epigallo-catechin-3-gallate (EGCG) encapsulated in poly(lactide-co-glycolic acid) (PLGA) particles to promote wound healing.

Methods

Nano- and microscale PLGA particles were fabricated using a water/oil/water emulsion solvent evaporation method. The optimal particle size was determined based on drug delivery efficiency and biocompatibility. The particles were loaded with EGCG. The anti-inflammatory effects of the particles were evaluated in an in vitro cell-based inflammation model.

Results

Nano- and microscale PLGA particles were produced. The microscale particles showed better biocompatibility than the nanoscale particles. In addition, the microscale particles released ~60% of the loaded drug, while the nanoscale particles released ~50%, within 48 hours. Thus, microscale particles were selected as the carriers. The optimal EGCG working concentration was determined based on the effects on cell viability and inflammation. A high EGCG dose (100 μM) resulted in poor cell viability; therefore, a lower dose (≤50 μM) was used. Moreover, 50 μM EGCG had a greater anti-inflammatory effect than 10 μM concentration on lipopolysaccharide-induced inflammation. Therefore, 50 μM EGCG was selected as the working dose. EGCG-loaded microparticles inhibited inflammation in human dermal fibroblasts. Interestingly, the inhibitory effects persisted after replacement of the drug-loaded particle suspension solution with fresh medium.

Conclusion

The EGCG-loaded microscale particles are biocompatible and exert a sustained anti-inflammatory effect.

EGFR inhibition by (-)-epigallocatechin-3-gallate and IIF treatments reduces breast cancer cell invasion

Epidermal growth factor receptor (EGFR) expression is an important marker in breast carcinoma pathology and is considered a pivotal molecule for cancer cell proliferation, invasion and metastasis. We investigated the effects of epigallocatechin-3-gallate (EGCG), the most active green tea catechin, in combination with 6-OH-11-O-hydroxyphenanthrene (IIF), a synthetic retinoid X receptor-γ (RXRγ) agonist, on three breast carcinoma cell lines: MCF-7, MCF-7TAM and MDA-MB-231. EGFR and AKT activation and molecular markers of cell motility and migration (CD44, extracellular matrix metalloproteinase (MMP) inducer (EMMPRIN), MMP-2, MMP-9 and tissue inhibitor of metalloproteinases (TIMPs)) were studied after EGCG and IIF treatments. The EGCG + IIF treatment was the most active in down-regulating EGFR phosphorylation at Tyr¹⁰⁶⁸ in all the investigated cell lines; p473AKT was also down-regulated in MCF-TAM cells. EGCG + IIF was also the most active treatment in reducing the expression of markers of invasion and migration in all the three cell lines: CD44, EMMPRIN, MMP-2 and -9 expression decreased, whereas TIMPs were up-regulated. Zymography and scratch assay also confirmed the reduced invasion tendency. We considered that EGCG and IIF treatments could alter the molecular network based on EGFR, CD44 and EMMPRIN expression interdependence and reduced the migration tendency in MCF-7, MCF-7TAM and MDA-MB-231 cells. These events only occurred in association with AKT inactivation in MCF-7TAM cells. In conclusion, the combination of EGCG and IIF significantly attenuated the invasive behaviour of breast carcinoma cells.