Development and Characterization of Reagent Pencils for Microfluidic Paper Based Analytical Devices

Microfluidic paper based analytical devices (microPADs) are a novel platform for point of care (POC) diagnostics. Limitations of reagent shelf life have been overcome with the introduction of reagent pencils as a method for solid-based reagent deposition. While useful, little work has been reported on the characterization and optimization of reagent pencils. Herein, an investigation on reagent pencil composition and efficiency is conducted via colorimetric release profile tests utilizing an erioglaucine disodium salt that yields a quantifiable blue colored product in the presence of water. Within this work, an investigation on the molecular weight dependence, polymer chain end functionality, and polymer-graphite ratio was conducted to determine the most desirable parameters in reagent pencil composition. Further, the effects of enzyme stability in the presence of poly(ethylene glycol) (PEG) is investigated. To show the versatility of reagent pencils, a novel reagent pencil incorporating a stimuli responsive polymer, poly(N-isporopylacrylamide) (PNIPAM) was developed. In this work, PNIPAM’s lower critical solution temperature (LCST) was manipulated with various salt solutions to control fluid flow both laterally and vertically through various microPAD designs. It was found that, while PNIPAM successfully blocked or retarded fluid flow in microPADs, the effect was limited when DI H2O wash solutions were run prior to salt solutions. To counteract this, PNIPAM was successfully covalently bound to alkene modified chromatography paper via thiolene click chemistry to reinforce solution wash tolerance

Characterization of reagent pencils for deposition of reagents onto paper-based microfluidic devices

Reagent pencils allow for solvent-free deposition of reagents onto paper-based microfluidic devices. The pencils are portable, easy to use, extend the shelf-life of reagents, and offer a platform for customizing diagnostic devices at the point of care. In this work, reagent pencils were characterized by measuring the wear resistance of pencil cores made from polyethylene glycols (PEGs) with different molecular weights and incorporating various concentrations of three different reagents using a standard pin abrasion test, as well as by measuring the efficiency of reagent delivery from the pencils to the test zones of paper-based microfluidic devices using absorption spectroscopy and digital image colorimetry. The molecular weight of the PEG, concentration of the reagent, and the molecular weight of the reagent were all found to have an inverse correlation with the wear of the pencil cores, but the amount of reagent delivered to the test zone of a device correlated most strongly with the concentration of the reagent in the pencil core. Up to 49% of the total reagent deposited on a device with a pencil was released into the test zone, compared to 58% for reagents deposited from a solution. The results suggest that reagent pencils can be prepared for a variety of reagents using PEGs with molecular weights in the range of 2000 to 6000 g/mol

Reagent pencils: A new technique for solvent-free deposition of reagents onto paper-based microfluidic devices

Custom-made pencils containing reagents dispersed in a solid matrix were developed to enable rapid and solvent-free deposition of reagents onto membrane-based fluidic devices. The technique is as simple as drawing with the reagent pencils on a device. When aqueous samples are added to the device, the reagents dissolve from the pencil matrix and become available to react with analytes in the sample. Colorimetric glucose assays conducted on devices prepared using reagent pencils had comparable accuracy and precision to assays conducted on conventional devices prepared with reagents deposited from solution. Most importantly, sensitive reagents, such as enzymes, are stable in the pencils under ambient conditions, and no significant decrease in the activity of the enzyme horseradish peroxidase stored in a pencil was observed after 63 days. Reagent pencils offer a new option for preparing and customizing diagnostic tests at the point of care without the need for specialized equipment

Glassy Polymersomes: Polymersomes: Breaking the Glass Ceiling?

In article number 1802734, Yoan C. Simon and co‐workers review the fabrication and usefulness of glassy polymersomes. Capitalizing on their noteworthy impermeability, rigidity, versatile assembly behavior, and readily available shape transformation, many groups have embarked on an exciting scientific journey to generate unique vesicular constructs, which could one day serve as cell mimics

Self-Assembly and Degradation of Photolabile Diblock Bottlebrushes

Aqueous self-assembly of amphiphilic block copolymers form diverse nanostructured morphologies depending on block volume fraction and solvophilicity. Stimuli-responsive motifs have been combined with self-assembled micelles to afford spatiotemporal, on-demand encapsulation and payload release. However, the role of modular polymer architecture (i.e., bottlebrushes) in stimuli-responsive aqueous self-assembly is not fully understood. The synthesis, aqueous self-assembly, and photoirradiation of photolabile, amphiphilic bottlebrush block copolymers is presented herein. Specifically, the efficient photoscission of o-nitrobenzene motifs at the junction of a poly(norbornene o-nitrobenzene polystyrene)-block-poly(norbornene polyethylene glycol) diblock bottlebrush side chain and backbone cleaved away hydrophobic polystyrene side chains and artificially increased the volume fraction of poly(ethylene glycol) (fPEG). In doing so, self-assembled micelles readily degrade to micelle-to-micelle and micelle-to-aggregate structures after photoirradiation. Finally, this bottlebrush micelle system is used to demonstrate the efficient encapsulation and stimuli-responsive release of Nile Red that is monitored by fluorescence spectroscopy and dynamic light scattering. The contribution of this work expands the utility of amphiphilic bottlebrush systems as highly efficient and responsive, hierarchically assembled nanomaterials

Modeling ultrasound-induced molecular weight decrease of polymers with multiple scissile azo-mechanophores

The azo moiety is receiving increasing attention as a stimuli-responsive trigger. Herein, we present an investigation of the mechanoresponsive behavior of a series of polyurethanes containing multiple randomly distributed azo motifs as scissile mechanophores, i.e., an entity that is preferentially cleaved upon application of a mechanical force. We made a systematic comparison of the ultrasound-induced cleavage of azo-containing polymers of different molecular weights and with varying azo content. We developed a mathematical model to describe the scission kinetics and the analysis of the rate constants showed that site-specific cleavage at the azo position was favored over random bond scission events. The proposed mathematical model appears to be a broadly useful method to characterize the ultrasound-induced molecular weight decrease of polymers containing multiple scissile mechanophores.Peer reviewe

Modeling Ultrasound-Induced Moledular Weight Decrease of Polymers With Multiple Scissile Azo-Mechanophores

The azo moiety is receiving increasing attention as a stimuli-responsive trigger. Herein, we present an investigation of the mechanoresponsive behavior of a series of polyurethanes containing multiple randomly distributed azo motifs as scissile mechanophores, i.e., an entity that is preferentially cleaved upon application of a mechanical force. We made a systematic comparison of the ultrasound-induced cleavage of azo-containing polymers of different molecular weights and with varying azo content. We developed a mathematical model to describe the scission kinetics and the analysis of the rate constants showed that site-specific cleavage at the azo position was favored over random bond scission events. The proposed mathematical model appears to be a broadly useful method to characterize the ultrasound-induced molecular weight decrease of polymers containing multiple scissile mechanophores

Forcing Single-Chain Nanoparticle Collapse Through Hydrophobic Solvent Interactions In Comb Copolymers

We introduce a novel synthetic strategy in which high molecular weight comb copolymers with aliphatic side chains can collapse into single-chain nanoparticles (SNCPs) via photodimerization of anthracene under ultraviolet (UV) irradiation. By deliberately selecting hydrophobic comonomers with disparate solvency, we demonstrated that we could control chain collapse. We attribute these results to the formation of pseudo-unimicellar structures, whereby polyisobutylene (PIB) side chains are preferentially solvated, thereby compressing anthracene moieties to form a denser crosslinked core. The control of hydrophobic interactions is a common occurrence in proteins and we believe that our approach can be further extended to achieve multi-compartment SCNPs whereby each section is responsible for a given function

WDR5 facilitates recruitment of N-MYC to conserved WDR5 gene targets in neuroblastoma cell lines

Abstract Collectively, the MYC family of oncoprotein transcription factors is overexpressed in more than half of all malignancies. The ability of MYC proteins to access chromatin is fundamental to their role in promoting oncogenic gene expression programs in cancer and this function depends on MYC–cofactor interactions. One such cofactor is the chromatin regulator WDR5, which in models of Burkitt lymphoma facilitates recruitment of the c-MYC protein to chromatin at genes associated with protein synthesis, allowing for tumor progression and maintenance. However, beyond Burkitt lymphoma, it is unknown whether these observations extend to other cancers or MYC family members, and whether WDR5 can be deemed as a “universal” MYC recruiter. Here, we focus on N-MYC amplified neuroblastoma to determine the extent of colocalization between N-MYC and WDR5 on chromatin while also demonstrating that like c-MYC, WDR5 can facilitate the recruitment of N-MYC to conserved WDR5-bound genes. We conclude based on this analysis that N-MYC and WDR5 colocalize invariantly across cell lines at predicted sites of facilitated recruitment associated with protein synthesis genes. Surprisingly, we also identify N-MYC-WDR5 cobound genes that are associated with DNA repair and cell cycle processes. Dissection of chromatin binding characteristics for N-MYC and WDR5 at all cobound genes reveals that sites of facilitated recruitment are inherently different than most N-MYC-WDR5 cobound sites. Our data reveals that WDR5 acts as a universal MYC recruiter at a small cohort of previously identified genes and highlights novel biological functions that may be coregulated by N-MYC and WDR5 to sustain the neuroblastoma state