Rapid prototyping of PDMS microdevices viaµPLAT on nonplanar surfaces with flexible hollow-out mask.

A major goal of polydimethylsiloxane (PDMS) microfabrication is to develop a simple and inexpensive method for rapid fabrication. Despite the recent advancements in this field, facile PDMS microfabrication on non-planar surfaces remains elusive. Here we report a facile method for rapid prototyping of PDMS microdevices viaµPLAT (microscale plasma-activated templating) on non-planar surfaces through micropatterning of hydrophilic/hydrophobic (HL/HB) interface by flexible polyvinyl chloride (PVC) hollow-out mask. This mask can be easily prepared with flexible PVC film through a cutting crafter and applied as pattern definer during the plasma treatment for microscale HL/HB interface formation on different substrates. The whole process requires low inputs in terms of time as well as toxic chemicals. Inspired by liquid molding, we demonstrated its use for rapid prototyping of PDMS microstructures. Following the proof-of-concept study, we also demonstrated the use of the flexible hollow-out mask to facilitate cell patterning on curved substrates, which is difficult to realize with conventional methods. Collectively, our work utilizes flexible and foldable PVC film as mask materials for facile microscale HL non-planar surface modification to establish a useful tool for PDMS prototyping and cell patterning.

Paper-Based 3D Scaffold for Multiplexed Single Cell Secretomic Analysis.

Despite rapid progresses in single-cell analysis technologies, efforts to control the three-dimensional microenvironment for single cell measurements have been lacking. Here, we report a simple method to incorporate three-dimensional scaffolds, including polyvinylidene fluoride (PVDF) membranes and PVDF membrane replicated analog polydimethylsiloxane, into multiplexed single cell secretomic analysis platforms (including a microwell array and a single cell barcode microchip) to mimic the extracellular physical matrix and mechanical support for single cells. Applying this platform to brain tumor cell line U87 to investigate single cell protein secretion behavior on different substrates, we revealed that single cell protein secretions were regulated differently in three-dimensional (3D) microenvironments. This finding was further verified with intracellular cytokine staining, highlighting the significance of 3D single cell microenvironments. This new single cell biomimetic platform can be easily adaptable to other three-dimensional cell culture scaffolds or other single cell assays and may become a broadly applicable three-dimensional single cell analysis system to study the effect of microenvironment conditions on cellular functional heterogeneity in vitro.

Mesoporous silica nanoparticles incorporated hybrid monolithic stationary phase immobilized with pepsin for enantioseparation by capillary electrochromatography.

In this study, a novel mesoporous silica nanoparticles incorporated chiral hybrid monolithic stationary phase was developed. The stationary phase was firstly prepared by an in situ copolymerization of amino-modified mesoporous silica nanoparticles (NH2-MSN), glycidyl methacrylate (GMA), and ethylene dimethacrylate (EDMA) and then functionalized with pepsin as chiral selector. The incorporated mesoporous silica nanoparticles provided additional interactions sites, and in turn yielded different enantioselectivity thus enhancing the overall separation. The column was successfully employed for enantioseparation of fifteen basic chiral drugs in capillary electrochromatography. Effects of nanoparticles percentage, pepsin concentration, the pH of running buffer and the applied voltage were investigated. All the analytes could be eluted in less than ten minutes and nine of them could achieve baseline separation. Satisfactory repeatabilities with relative standard deviations less than 4.2% were achieved through intraday, interday, column-to-column and batch-to-batch investigations. These results indicated that the simultaneous utilization of the unique properties of mesoporous silica nanoparticles and versatile features of monoliths could be a promising strategy for enantioseparation.

Carboxylated single-walled carbon nanotube-functionalized chiral polymer monoliths for affinity capillary electrochromatography.

Carboxylated single-walled carbon nanotubes (c-SWNTs) were incorporated into poly(glycidylmethacrylate-co-ethylene glycol dimethacrylate) [poly(GMA-co-EDMA)] monoliths to develop a novel monolithic stationary phase for capillary electrochromatography. The prepared monoliths were characterized by scanning electron microscopy and nitrogen adsorption. Additionally, pepsin, which is a chiral selector, was bonded to the c-SWNT-incorporated monoliths via epoxide groups as reactive sites and glutaraldehyde as the spacer. The effects of the c-SWNT concentration on chiral separation were investigated, and the results suggested that the c-SWNTs played a significant role in improving the separation efficiency, although pepsin was the dominant element in determining the chiral recognition ability of the monolith. Moreover, the influences of buffer pH, operating voltage and sample volume were also studied with (±)-nefopam as a model drug. Under the optimized conditions, the pepsin-modified poly(GMA-c-SWNTs-EDMA) monolith exhibited excellent enantioseparation performance for ten pairs of basic chiral drugs and extended the scope of chiral separation of drug enantiomers.

Preparation of graphene oxide-modified affinity capillary monoliths based on three types of amino donor for chiral separation and proteolysis.

Novel graphene oxide (GO)-modified affinity capillary monoliths were developed employing human serum albumin (HSA) or pepsin as chiral selector. Three types of amino donors for GO immobilization, including ammonium hydroxide (NH4OH), ethanediamine (EDA) and polyethyleneimine (PEI), were applied to explore the effect of spacer arm on enantioseparation. It was observed that HSA-GO-EDA-based affinity capillary monoliths exhibited better chiral recognition ability in comparison with the other two spacer-based monoliths. Under the optimized conditions, the obtained columns revealed satisfactory repeatability concerning column-to-column, run-to-run and interday repeatability. In addition, the impact of GO concentration on enantiomeric separation was also investigated. HSA-GO-EDA-based affinity capillary monoliths provided higher chiral selectivity for nine pairs of enantiomers compared to the columns without GO. Furthermore, the influence of amino donors and GO on proteolytic activity of pepsin-based immobilized enzymatic reactor (IMER) was discussed. Unfortunately, pepsin-GO-PEI-based affinity capillary monoliths possessed the highest protein digestion capacity, which was different from the effect of amino donors on enantiorecognition. Moreover, GO presented as a favorable choice to improve the enzymatic activity of IMER. These results proved that GO-functionalized affinity capillary monoliths have promising potential for chiral separation and proteolysis.