A novel microporous biomaterial vaccine platform for long-lasting antibody mediated immunity against viral infection.

Current antigen delivery platforms, such as alum and nanoparticles, are not readily tunable, thus may not generate optimal adaptive immune responses. We created an antigen delivery platform by loading lyophilized Microporous Annealed Particle (MAP) with aqueous solution containing target antigens. Upon administration of antigen loaded MAP (VaxMAP), the biomaterial reconstitution forms an instant antigen-loaded porous scaffold area with a sustained release profile to maximize humoral immunity.

Activating an adaptive immune response from a hydrogel scaffold imparts regenerative wound healing.

Microporous annealed particle (MAP) scaffolds are flowable, in situ crosslinked, microporous scaffolds composed of microgel building blocks and were previously shown to accelerate wound healing. To promote more extensive tissue ingrowth before scaffold degradation, we aimed to slow MAP degradation by switching the chirality of the crosslinking peptides from L- to D-amino acids. Unexpectedly, despite showing the predicted slower enzymatic degradation in vitro, D-peptide crosslinked MAP hydrogel (D-MAP) hastened material degradation in vivo and imparted significant tissue regeneration to healed cutaneous wounds, including increased tensile strength and hair neogenesis.

Particle Hydrogels Based on Hyaluronic Acid Building Blocks.

The extracellular matrix (ECM) provides tissues with the mechanical support, space, and bioactive signals needed for homeostasis or tissue repair after wounding or disease. Hydrogel based scaffolds that can match the bulk mechanical properties of the target tissue have been extensively explored as ECM mimics. Although the addition of microporosity to hydrogel scaffolds has been shown to enhance cell/tissue-material integration, the introduction of microporosity often involves harsh chemical methods, which limit bioactive signal incorporation and injectability.

Accelerated wound healing by injectable microporous gel scaffolds assembled from annealed building blocks.

Injectable hydrogels can provide a scaffold for in situ tissue regrowth and regeneration, yet gel degradation before tissue reformation limits the gels' ability to provide physical support. Here, we show that this shortcoming can be circumvented through an injectable, interconnected microporous gel scaffold assembled from annealed microgel building blocks whose chemical and physical properties can be tailored by microfluidic fabrication. In vitro, cells incorporated during scaffold formation proliferated and formed extensive three-dimensional networks within 48 h.

Sugar additives improve signal fidelity for implementing two-phase resorufin-based enzyme immunoassays.

Enzymatic signal amplification based on fluorogenic substrates is commonly used for immunoassays; however, when transitioning these assays to a digital format in water-in-mineral oil emulsions, such amplification methods have been limited by the leakage of small reporting fluorescent probes. In the present study, we used a microfluidic system to study leakage from aqueous droplets in a controlled manner and confirmed that the leakage of fluorescent resorufin derivatives is mostly due to the presence of the lipophilic surfactant Span80, which is commonly used to preserve emulsion stability. This leakage can be overcome by the addition of specific sugars that most strongly interfered with the surfactants ability to form micelles in water.

Advances in high-throughput single-cell microtechnologies.

Micro-scale biological tools that have allowed probing of individual cells--from the genetic, to proteomic, to phenotypic level--have revealed important contributions of single cells to direct normal and diseased body processes. In analyzing single cells, sample heterogeneity between and within specific cell types drives the need for high-throughput and quantitative measurement of cellular parameters. In recent years, high-throughput single-cell analysis platforms have revealed rare genetic subpopulations in growing tumors, begun to uncover the mechanisms of antibiotic resistance in bacteria, and described the cell-to-cell variations in stem cell differentiation and immune cell response to activation by pathogens.

Research highlights: microfluidics meets big data.

In this issue we highlight a collection of recent work in which microfluidic parallelization and automation have been employed to address the increasing need for large amounts of quantitative data concerning cellular function--from correlating microRNA levels to protein expression, increasing the throughput and reducing the noise when studying protein dynamics in single-cells, and understanding how signal dynamics encodes information. The painstaking dissection of cellular pathways one protein at a time appears to be coming to an end, leading to more rapid discoveries which will inevitably translate to better cellular control--in producing useful gene products and treating disease at the individual cell level. From these studies it is also clear that development of large scale mutant or fusion libraries, automation of microscopy, image analysis, and data extraction will be key components as microfluidics contributes its strengths to aid systems biology moving forward.

Size-selective collection of circulating tumor cells using Vortex technology.

A blood-based, low cost alternative to radiation intensive CT and PET imaging is critically needed for cancer prognosis and management of its treatment. "Liquid biopsies" of circulating tumor cells (CTCs) from a relatively non-invasive blood draw are particularly ideal, as they can be repeated regularly to provide up to date molecular information about the cancer, which would also open up key opportunities for personalized therapies. Beyond solely diagnostic applications, CTCs are also a subject of interest for drug development and cancer research.

Increased asymmetric and multi-daughter cell division in mechanically confined microenvironments.

As the microenvironment of a cell changes, associated mechanical cues may lead to changes in biochemical signaling and inherently mechanical processes such as mitosis. Here we explore the effects of confined mechanical environments on cellular responses during mitosis. Previously, effects of mechanical confinement have been difficult to optically observe in three-dimensional and in vivo systems.

Intrinsic particle-induced lateral transport in microchannels.

In microfluidic systems at low Reynolds number, the flow field around a particle is assumed to maintain fore-aft symmetry, with fluid diverted by the presence of a particle, returning to its original streamline downstream. This current model considers particles as passive components of the system. However, we demonstrate that at finite Reynolds number, when inertia is taken into consideration, particles are not passive elements in the flow but significantly disturb and modify it.

Fluid flow induces biofilm formation in Staphylococcus epidermidis polysaccharide intracellular adhesin-positive clinical isolates.

Staphylococcus epidermidis is a common cause of catheter-related bloodstream infections, resulting in significant morbidity and mortality and increased hospital costs. The ability to form biofilms plays a crucial role in pathogenesis; however, not all clinical isolates form biofilms under normal in vitro conditions. Strains containing the ica operon can display significant phenotypic variation with respect to polysaccharide intracellular adhesin (PIA)-based biofilm formation, including the induction of biofilms upon environmental stress.

The effects of shear stress on isolated receptor-ligand interactions of Staphylococcus epidermidis and human plasma fibrinogen using molecularly patterned microfluidics.

Staphylococcus epidermidis is an opportunistic pathogen that has been implicated in hospital-acquired infections, specifically related to implanted intravascular devices. S. epidermidis adhesion is a mechanism of colonization, leading to pathogenesis.

Sequential array cytometry: multi-parameter imaging with a single fluorescent channel.

Heterogeneity within the human population and within diseased tissues necessitates a personalized medicine approach to diagnostics and the treatment of diseases. Functional assays at the single-cell level can contribute to uncovering heterogeneity and ultimately assist in improved treatment decisions based on the presence of outlier cells. We aim to develop a platform for high-throughput, single-cell-based assays using well-characterized hydrodynamic cell isolation arrays which allow for precise cell and fluid handling.

Label-free cell separation and sorting in microfluidic systems.

Cell separation and sorting are essential steps in cell biology research and in many diagnostic and therapeutic methods. Recently, there has been interest in methods which avoid the use of biochemical labels; numerous intrinsic biomarkers have been explored to identify cells including size, electrical polarizability, and hydrodynamic properties. This review highlights microfluidic techniques used for label-free discrimination and fractionation of cell populations.