Direct Fabrication of Glycoengineered Cells via Photoresponsive Thiol-ene Reaction

Three-dimensional printing of cell constructs with high-cell density, shape fidelity, and heterogeneous cell populations is an important tool for investigating cell sociology in living tissues but remains challenging. Herein, we propose an artificial intercellular adhesion method using a photoresponsive chemical cue between a thiol-bearing polymer and a methacrylate-bearing cell membrane. This process provided cell fabrication containing 108 cells/mL, embedded multiple cell populations in one structure, and enabled millimeter-sized scaleup. Our approach allows for the artificial cell construction of complex structures and is a promising bioprinting strategy for engineering tissues that are structurally and physiologically relevant.

Increased Retention of Cardiac Cells to a Glass Substrate through Streptavidin-Biotin Affinity

In vitro analysis of primary isolated adult cardiomyocyte physiological processes often involves optical imaging of dye-loaded cells on a glass substrate. However, when exposed to rapid solution changes, primary cardiomyocytes often move to compromise quantitative measures. Improved immobilization of cells to glass would permit higher throughput assays. Here, we engineer the peripheral membrane of cardiomyocytes with biotin to anchor cardiomyocytes to borosilicate glass coverslips functionalized with streptavidin. We use a rat cardiac myoblast cell line to determine general relationships between processing conditions, ligand density on the cell and the glass substrate, cellular function, and cell retention under shear flow. Use of the streptavidin-biotin system allows for more than 80% retention of cardiac myoblasts under conventional rinsing procedures, while unmodified cells are largely rinsed away. The adhesion system enables the in-field retention of cardiac cells during rapid fluid changes using traditional pipetting or a modern microfluidic system at a flow rate of 160 mL/min. Under fluid flow, the surface-engineered primary adult cardiomyocytes are retained in the field of view of the microscope, while unmodified cells are rinsed away. Importantly, the engineered cardiomyocytes are functional following adhesion to the glass substrate, where contractions are readily observed. When applying this adhesion system to cardiomyocyte functional analysis, we measure calcium release transients by caffeine induction at an 80% success rate compared to 20% without surface engineering.

Increased yield of gelatin coated therapeutic cells through cholesterol insertion

Gelatin coatings are effective in increasing the retention of MSCs injected into the heart and minimizing the damage from acute myocardial infarction (AMI), but early studies suffered from low fractions of the MSCs coated with gelatin. Biotinylation of the MSC surface is a critical first step in the gelatin coating process, and in this study, we evaluated the use of biotinylated cholesterol "lipid insertion" anchors as a substitute for the covalent NHS-biotin anchors to the cell surface. Streptavidin-eosin molecules, where eosin is our photoinitiator, can then be bound to the cell surface through biotin-streptavidin affinity. The use of cholesterol anchors increased streptavidin density on the surface of MSCs further driving polymerization and allowing for an increased fraction of MSCs coated with gelatin (83%) when compared to NHS-biotin (52%). Additionally, the cholesterol anchors increased the uniformity of the coating on the MSC surface and supported greater numbers of coated MSCs even when the streptavidin density was slightly lower than that of an NHS-biotin anchoring strategy. Critically, this improvement in gelatin coating efficiency did not impact cytokine secretion and other critical MSC functions. Proper selection of the cholesterol anchor and the biotinylation conditions supports cellular function and densities of streptavidin on the MSC surface of up to ~105 streptavidin molecules/μm2 . In all, these cholesterol anchors offer an effective path towards the formation of conformal coatings on the majority of MSCs to improve the retention of MSCs in the heart following AMI.

Coatings on mammalian cells: interfacing cells with their environment

The research community is intent on harnessing increasingly complex biological building blocks. At present, cells represent a highly functional component for integration into higher order systems. In this review, we discuss the current application space for cellular coating technologies and emphasize the relationship between the target application and coating design. We also discuss how the cell and the coating interact in common analytical techniques, and where caution must be exercised in the interpretation of results. Finally, we look ahead at emerging application areas that are ideal for innovation in cellular coatings. In all, cellular coatings leverage the machinery unique to specific cell types, and the opportunities derived from these hybrid assemblies have yet to be fully realized.

Improved Performance of DNA Microarray Multiplex Hybridization Using Probes Anchored at Several Points by Thiol-Ene or Thiol-Yne Coupling Chemistry

Nucleic acid microarray-based assay technology has shown lacks in reproducibility, reliability, and analytical sensitivity. Here, a new strategy of probe attachment modes for silicon-based materials is built up. Thus, hybridization ability is enhanced by combining thiol-ene or thiol-yne click chemistry reactions with a multipoint attachment of polythiolated probes. The viability and performance of this approach was demonstrated by specifically determining Salmonella PCR products up to a 20 pM sensitivity level.

Surface engineering of macrophages with nucleic acid aptamers for the capture of circulating tumor cells

In order to enhance the interactions between macrophages and cancer cells, thiol-terminated nucleic acid aptamers were immobilized on methacryloyl-functionalised carbohydrates of macrophages. The adhesion of cancer cells on the surface modified macrophages was significantly accelerated.

High-throughput superhydrophobic microwell arrays for investigating multifactorial stem cell niches

Understanding the complex regulatory network that determines stem cell fates requires a high-throughput platform that can generate a large number of precisely controlled microenvironments representing multiple factors for stem cell culture and analysis. Here, we developed a superhydrophobic microwell array chip on which the culture conditions in each microwell can be spontaneously isolated by a grafted layer of superhydrophobic polymers. Simple steps for medium exchange were developed to facilitate the on-chip culture of both adherent and non-adherent cells for up to six days without compromising cell viability and functionality. The culture conditions in each microwell were facilely manipulated using a robotic spotter. Stem cell niches combining soluble factors, extracellular matrices and microtopographic cues were generated on a single 512-well SMARchip and their combinatorial effects on the fate of mouse Oct4-EGFP iPSCs were systematically probed. We observed significant differences in iPSC pluripotency and proliferation between adherent flat and suspended spherical cultures on our platform, which might provide insights into improvement of stem cell technologies.

Preparation of biointeractive glycoprotein-conjugated hydrogels through metabolic oligosacchalide engineering

In the current study, synthetic hydrogels containing metabolically engineered glycoproteins of mammalian cells were prepared for the first time and selectin-mediated cell adhesion on the hydrogel was demonstrated. A culture of HL-60 cells was supplemented with an appropriate volume of aqueous solution of N-methacryloyl mannosamine (ManMA) to give a final concentration of 5 mM. The cells were then incubated for 3 days to deliver methacryloyl groups to the glycoproteins of the cells. A transparent hydrogel was formed via redox radical polymerization of methacryloyl functionalized glycoproteins with 2-methacryloyloxyethyl phosphorylcholine and a cross-linker. Conjugation of the glycoproteins into the hydrogel was determined using Coomassie brilliant blue (CBB) and periodic acid-Schiff (PAS) staining. The surface density of P-selectin glycoprotein ligand-1 (PSGL-1) on the hydrogels was also detected using gold-colloid-labeled immunoassay. Finally, selectin-mediated cell adhesion on hydrogels containing glycoproteins was demonstrated. Selectin-mediated cell adhesion is considered an essential step in the progression of various diseases; therefore, hydrogels having glycoproteins could be useful in therapeutic and diagnostic applications.

Nano-decoration of the Hemagglutinating Virus of Japan envelope (HVJ-E) using a layer-by-layer assembly technique

In this study, we created a nanoscale layer of hyaluronic acid (HA) on the inactivated Hemagglutinating Virus of Japan envelope (HVJ-E) via a layer-by-layer (LbL) assembly technique for CD-44 targeted delivery. HVJ-E was selected as the template virus because it has shown a tumor-suppressing ability by eliciting inflammatory cytokine production in dendritic cells. Although it has been required to increase the tumor-targeting ability and reduce nonspecific binding because HVJ-E fuses with virtually all cells and induces hemagglutination in the bloodstream, complete modifications of single-envelope-type viruses with HA have been difficult. Therefore, we studied the surface ζ potential of HVJ-E at different pH values and carefully examined the deposition conditions for the first layer using three cationic polymers: poly-L-lysine (PLL), chitosan (CH), and glycol chitosan (GC). GC-coated HVJ-E particles showed the highest disperse ability under physiological pH and salt conditions without aggregation. An HA layer was then prepared via alternating deposition of HA and GC. The successive decoration of multilayers on HVJ-E has been confirmed by dynamic light scattering (DLS), ζ potentials, and transmission electron microscopy (TEM). An enzymatic degradation assay revealed that only the outermost HA layer was selectively degraded by hyaluronidase. However, entire layers were destabilized at lower pH. Therefore, the HA/GC-coated HVJ-E describe here can be thought of as a potential bomb for cancer immunotherapy because of the ability of targeting CD44 as well as the explosion of nanodecorated HA/GC layers at endosomal pH while preventing nonspecific binding at physiological pH and salt conditions such as in the bloodstream or normal tissues.

Synthesis of biotin linkers with the activated triple bond donor [p-(N-propynoylamino)toluic acid] (PATA) for efficient biotinylation of peptides and oligonucleotides

Biotin is an important molecule for modern biological studies including, e.g., cellular transport. Its exclusive affinity to fluorescent streptavidin/avidin proteins allows ready and specific detection. As a consequence methods for the attachment of biotin to various biological targets are of high importance, especially when they are very selective and can also proceed in water. One useful method is Hüisgen dipolar [3+2]-cycloaddition, commonly referred to as “click chemistry”. As we reported recently, the activated triple bond donor p-(N-propynoylamino)toluic acid (PATA) gives excellent results when used for conjugations at submicromolar concentrations. Thus, we have designed and synthesized two biotin linkers, with different lengths equipped with this activated triple bond donor and we proceeded with biotinylation of oligonucleotides and C-myc peptide both in solution and on solid support with excellent yields of conversion.

A Four-Arm Star-Shaped Poly(ethylene glycol) (StarPEG) Platform for Bombesin Peptide Delivery to Gastrin-Releasing Peptide Receptors in Prostate Cancer

We present the design, synthesis, and characterization of a novel cancer biomarker delivery platform, the star-shaped four-arm poly(ethylene glycol) (StarPEG). Using the multidisplay platform we were able to synthesize a bombesin (BBN) positron emission tomography (PET) probe featuring four copies of 8-Aoc-BBN peptides (where 8-Aoc is 8-aminooctanic acid), which we named StarPEG-BBN. Cell binding studies showed that StarPEG-BBN had a good binding affinity to PC3 cells (IC₅₀ = 65.3 ± 3.4 nM). Cell uptake studies showed that the binding was specific (blocking vs no-blocking, P < 0.05). Mice were then implanted with PC3 cells and divided into two groups, one injected with ⁶⁴Cu-StarPEG-BBN and the other 250 μg of unlabeled 8-Aoc-BBN along with ⁶⁴Cu-StarPEG-BBN. In vivo images revealed that StarPEG-BBN had good tumor uptake (4.2 ± 0.4% ID/g at 4 h post-injection (p.i.)) and was significantly blocked by coinjection of unlabeled 8-Aoc-BBN at 4 h p.i. (P = 0.003). The small animal PET quantification was further verified by the biodistribution study at 24 h p.i. Our study demonstrated that the novel four-arm PEG platform StarPEG as a cancer biomarker multimerization/delivery platform conserves binding specificity, improves drug loading, is capable of achieving good tumor uptake, and has great potential in cancer treatment and molecular imaging.