Quantifying Cell Confluency by Plasmonic Nanodot Arrays to Achieve Cultivating Consistency

Plasmonic Au@Ag Core-Shell Nanoisland Film for Photothermal Inactivation and Surface-Enhanced Raman Scattering Detection of Bacteria

Plasmonic metal nanomaterials have been extensively investigated for their utilizations in biomedical sensing and treatment. In this study, plasmonic Au@Ag core-shell nanoisland films (Au@AgNIFs) were successfully grown onto a glass substrate using a seed-mediated growth procedure. The nanostructure of the Au@AgNIFs was confirmed through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and atomic force microscopy (AFM). The UV-Vis spectra of the Au@AgNIFs exhibited a broad absorption in the visible range from 300 to 800 nm because of the surface plasmon absorption. Under simulated sunlight exposure, the temperature of optimal Au@AgNIF was increased to be 66.9 °C to meet the requirement for photothermal bacterial eradication. Furthermore, the Au@AgNIFs demonstrated a consistent photothermal effect during the cyclic on/off exposure to light. For photothermal therapy, the Au@AgNIFs revealed superior efficiency in the photothermal eradication of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). With their unique nanoisland nanostructure, the Au@AgNIFs exhibited excellent growth efficiency of bacteria in comparison with that of the bare glass substrate. The Au@AgNIFs were also validated as a surface-enhanced Raman scattering (SERS) substrate to amplify the Raman signals of E. coli and S. aureus. By integrating photothermal therapy and SERS detection, the Au@AgNIFs were revealed to be a potential platform for bacterial theranostics.

Differentiation, maturation, and collection of THP-1-derived dendritic cells based on a PEG hydrogel culture platform

PURPOSE

Dendritic cell (DC) is a spearhead responsible for immune response and surrounded by extracellular matrix in three-dimensional (3D) tissue. Nevertheless, conventional DC culture has relied on suspension or two-dimensional (2D) tissue culture plate (TCP)-based culture system. This culture condition often fails to recapitulate the physiological behavior of DC in real tissue. In this work, the effect of culture condition on DC physiology was explored with varying 3D hydrogel property (i.e., degradability, adhesion, and stiffness). In particular, DC differentiation and maturation in 3D were evaluated comparing the conventional TCP-based culture condition.

METHOD

THP-1 cells were encapsulated in poly(ethylene glycol) (PEG) hydrogel via thiol-ene photocrosslinking with non-degradable or proteolytically degradable peptide crosslinker. Hydrogel stiffness was manipulated by controlling the concentration of crosslinker. The metabolic activities and cytotoxicity of the encapsulated cells were measured by resazurin and Live/Dead assays, respectively. Cell harvesting was conducted via enzymatic degradation using α-chymotrypsin, and differentiation and maturation of the liberated DCs were evaluated by quantitative polymerase chain reaction and flow cytometry.

RESULTS

THP-1 cells well proliferated in the soft degradable hydrogel with a higher metabolic activity. However, the stiff matrix inhibited cell growth in 3D. The gene expression assay indicated that the 3D hydrogel condition was superior to 2D culture in terms of differentiation and maturation of DC. Interestingly, the stiffness of matrix was important factor in DC function. In the stiff hydrogel, the expression levels of differentiation and maturation markers were higher compared to the low stiffness hydrogel. The mature DCs caged in the hydrogel matrix were harvested after short enzymatic digestion of hydrogel and the liberated cells had over 90% viability. The flow cytometric result revealed that the proportion of CD80 + /CD86 + cells from the stiff hydrogel was relatively higher than cells either from 2D or soft hydrogel in 3D.

CONCLUSION

The collected evidence indicated that the proteolytically degradable PEG hydrogel matrix promoted DC differentiation and maturation. In addition, the matrix stiffness control could manipulate the marker expressions of differentiation and maturation. Particularly, the mature DC was successfully collected from the hydrogel matrix. These results highlighted the PEG hydrogel-based DC culture might be a useful tool for potential DC-based immunotherapies.

Gold-Based Nanostructures for Antibacterial Application

Bacterial infections have become a fatal threat because of the abuse of antibiotics in the world. Various gold (Au)-based nanostructures have been extensively explored as antibacterial agents to combat bacterial infections based on their remarkable chemical and physical characteristics. Many Au-based nanostructures have been designed and their antibacterial activities and mechanisms have been further examined and demonstrated. In this review, we collected and summarized current developments of antibacterial agents of Au-based nanostructures, including Au nanoparticles (AuNPs), Au nanoclusters (AuNCs), Au nanorods (AuNRs), Au nanobipyramids (AuNBPs), and Au nanostars (AuNSs) according to their shapes, sizes, and surface modifications. The rational designs and antibacterial mechanisms of these Au-based nanostructures are further discussed. With the developments of Au-based nanostructures as novel antibacterial agents, we also provide perspectives, challenges, and opportunities for future practical clinical applications.

Volumetric imaging of human mesenchymal stem cells (hMSCs) for non-destructive quantification of 3D cell culture growth

The adoption of cell-based therapies into the clinic will require tremendous large-scale expansion to satisfy future demand, and bioreactor-microcarrier cultures are best suited to meet this challenge. The use of spherical microcarriers, however, precludes in-process visualization and monitoring of cell number, morphology, and culture health. The development of novel expansion methods also motivates the advancement of analytical methods used to characterize these microcarrier cultures. A robust optical imaging and image-analysis assay to non-destructively quantify cell number and cell volume was developed. This method preserves 3D cell morphology and does not require membrane lysing, cellular detachment, or exogenous labeling. Complex cellular networks formed in microcarrier aggregates were imaged and analyzed in toto. Direct cell enumeration of large aggregates was performed in toto for the first time. This assay was successfully applied to monitor cellular growth of mesenchymal stem cells attached to spherical hydrogel microcarriers over time. Elastic scattering and fluorescence lightsheet microscopy were used to quantify cell volume and cell number at varying spatial scales. The presented study motivates the development of on-line optical imaging and image analysis systems for robust, automated, and non-destructive monitoring of bioreactor-microcarrier cell cultures.

GEMA-An Automatic Segmentation Method for Real-Time Analysis of Mammalian Cell Growth in Microfluidic Devices

Nowadays, image analysis has a relevant role in most scientific and research areas. This process is used to extract and understand information from images to obtain a model, knowledge, and rules in the decision process. In the case of biological areas, images are acquired to describe the behavior of a biological agent in time such as cells using a mathematical and computational approach to generate a system with automatic control. In this paper, MCF7 cells are used to model their growth and death when they have been injected with a drug. These mammalian cells allow understanding of behavior, gene expression, and drug resistance to breast cancer. For this, an automatic segmentation method called GEMA is presented to analyze the apoptosis and confluence stages of culture by measuring the increase or decrease of the image area occupied by cells in microfluidic devices. In vitro, the biological experiments can be analyzed through a sequence of images taken at specific intervals of time. To automate the image segmentation, the proposed algorithm is based on a Gabor filter, a coefficient of variation (CV), and linear regression. This allows the processing of images in real time during the evolution of biological experiments. Moreover, GEMA has been compared with another three representative methods such as gold standard (manual segmentation), morphological gradient, and a semi-automatic algorithm using FIJI. The experiments show promising results, due to the proposed algorithm achieving an accuracy above 90% and a lower computation time because it requires on average 1 s to process each image. This makes it suitable for image-based real-time automatization of biological lab-on-a-chip experiments.

Disposable Polymeric Nanostructured Plasmonic Biosensors for Cell Culture Adhesion Monitoring

Over the last years, optical biosensors based on plasmonic nanomaterials have gained great scientific interest due to their unquestionable advantages compared to other biosensing technologies. They can achieve sensitive, direct, and label-free analysis with exceptional potential for multiplexing and miniaturization. Recently, it has been demonstrated the potential of using optical discs as high throughput nanotemplates for the development of plasmonic biosensors in a cost-effective way. This work is a pilot study focused on the development of an integrated plasmonic biosensor for the monitoring of cell adhesion and growth of human retinal pigmented cell line (ARPE-19) under different media conditions (0 and 2% of FBS). We observed an increase of the plasmonic band displacement under 2% FBS compared to 0% conditions over time (1, 3, and 5 h). These preliminary results show that the proposed plasmonic biosensing approach is a direct, non-destructive, and real-time tool that could be employed in the study of living cells behavior and culture conditions. Furthermore, this setup could assess the viability of the cells and their growth over time with low variability between the technical replicates improving the experimental replicability.

A novel method of cell culture based on the microfluidic chip for regulation of cell density

The regulation of cell density is an important segment in microfluidic cell culture, particularly in the repeated assays. Traditionally, consistent cell density is difficult to achieve, owing to the inaccurate regulation of cell density with manual feedback. A novel cell culture method with automatic feedback is proposed for real-time regulation of cell density based on microfluidic chip in this paper. Here, an integrated microfluidic system combining cell culture, density detection, and control of proliferation rate was developed. Interdigital electrode structures were sputtered on the microchannel automatically to provide the real-time feedback information of impedance. The most sensitive frequency was studied to improve the detection resolution of the sensing chip. Cells were cultured on the chip surface and cell density was detected by monitoring the alternation of the impedance. The feedback controller was established by the least squares support vector machines. Then, the cell proliferation rate was automatically controlled using the feedback controller to achieve the desired cell density in the repeated assays. The results show that the standard error of this method is 2.8% indicating that the method can keep a consistency of cell density in the repeated assays. This study provides a basis for improving the accuracy and repeatability in the further assays of finding the optimal drug concentration.