A series of ABC triblock copolypeptoids [i.e., poly(N-allyl glycine)-b-poly(N-methyl glycine)-b-poly(N-decyl glycine) (AMD)] with well-defined structure and varying composition have been synthesized by sequential primary amine-initiated ring-opening polymerization of the corresponding N-substituted N-carboxyanhydride monomers (Al-NCA, Me-NCA, and De-NCA). The ABC block copolypeptoids undergo sol-to-gel transitions with increasing temperature in water and biological media at low concentrations (2.5–10 wt %). The sol–gel transition is rapid and fully reversible with a narrow transition window, evidenced by the rheological measurements. The gelation temperature (Tgel) and mechanical stiffness of the hydrogels are highly tunable: Tgel in the 26.2–60.0 °C range, the storage modulus (G′) and Young’s modulus (E) in the 0.2–780 Pa and 0.5–2346 Pa range, respectively, at the physiological temperature (37 °C) can be readily accessed by controlling the block copolypeptoid composition and the polymer solution concentration. The hydrogel is injectable through a 24 gauge syringe needle and maintains their shape upon in contact with surfaces or water baths that are kept above the sol–gel transition temperature. The hydrogels exhibit minimal cytotoxicity toward human adipose derived stem cells (hASCs), evidenced from both alamarBlue and PicoGreen assays. Furthermore, quantitative PCR analysis revealed significant up-regulation of the Col2a1 gene and down-regulation of ANGPT1 gene, suggesting that the hydrogel exhibit biological activity in inducing chondrogenesis of hASCs. It was also demonstrated that the hydrogel can be used to quantitatively encapsulate water-soluble enzymes (e.g., horseradish peroxidase) by manipulating the sol–gel transition. The enzymatic activity of HRP remain unperturbed after encapsulation at 37 °C for up to 7 d, suggesting that the hydrogel does not adversely affect the enzyme structure and thereby the enzymatic activity. These results suggest that the polypeptoid hydrogel a promising synthetic platform for tissue engineering or protein storage applications.

Magnetic beads are a popular method for concentrating biomolecules from solution and have been more recently used in multistep pre-arrayed microfluidic cartridges. Typical processing strategies rely on a single magnet, resulting in a tight cluster of beads and requiring long incubation times to achieve high capture efficiencies, especially in highly viscous patient samples. This report describes a two-magnet strategy to improve the interaction of the bead surface with the surrounding fluid inside of a pre-arrayed, self-contained assay-in-a-tube. In the two-magnet system, target biomarker capture occurs at a rate three times faster than the single-magnet system. In clinically relevant biomatrices, we find a 2.5-fold improvement in biomarker capture at lower sample viscosities with the two-magnet system. In addition, we observe a 20% increase in the amount of protein captured at high viscosity for the two-magnet configuration relative to the single magnet approach. The two-magnet approach offers a means to achieve higher biomolecule extraction yields and shorter assay times in magnetic capture assays and in self-contained processor designs.

PCR is the most sensitive molecular diagnostic available for infectious diseases. The goal for low-resource settings is a simple, inexpensive instrument. Toward this goal, we previously published a self-contained sample preparation instrument that uses magnetics and prearrayed reagents in thin tubing to extract nucleic acids and perform isothermal amplification and detection of extracted biomarkers. To incorporate PCR thermal cycling, after biomarker is magnetically extracted from a patient sample, the section of tubing containing the extracted biomarker and PCR reagents is alternately positioned within two constant temperature blocks. This instrument was evaluated initially by extracting and amplifying a 140 bp fragment of the IS6110 sequence of tuberculosis from TE buffer. The mean cycle threshold for 5 × 10 6 copies of IS6110 was 25.5 ± 1.5 cycles (n = 4), which was significantly different from negative control samples (34.0 ± 2.6 cycles; n = 3). Using a more clinically relevant sample, we extracted and amplified Plasmodium falciparum DNA from malaria-infected human blood cultures. The average cycle threshold for 1% parasitemia samples was 24.7 ± 1.5 cycles (n = 3) and significantly different from negatives (31.5 ± 2.1 cycles; n = 3). This approach integrates biomarker extraction, PCR amplification, and detection in a simple, linear tubing design with potential for use as a low-resource instrument.