Qiaosheng Pu

Many methods have been established for determining the molecular weight of polymers; however, significant challenges remain when the polymers are highly charged, largely due to the so-called "polyelectrolyte effect". In this work, the molecular weight of polyelectrolytes was evaluated based on their adsorption kinetics onto oppositely charged surfaces in a microchannel by pulsed streaming potential (SP) measurements. The initial rate constant (k_i) was found to be dependent on the molecular weight of a polyelectrolyte under controlled experimental conditions. Assuming that adsorption at the initial stage is diffusion controlled, k_i is approximately proportional to M^b, where M is the average molecular weight of the polyelectrolyte and b is an empirically determined constant for the system. By flushing the polyelectrolyte solution through a capillary with an oppositely charged surface, the initial adsorption change rate (dE_r/dt) was obtained within 20 s, and k_i was derived from measurements at five different concentrations in about 3 min. Cationic (poly(diallyldimethylammonium chloride) (PDDA) and poly-l-lysine hydrobromide (PLL)) and anionic (poly(acrylic acid) (PAA) and poly(styrenesulfonic acid sodium salt) (PSS)) polyelectrolytes with different molecular weights were used to determine k_i values. The results confirmed that k_i is proportional to M^b and that b is a fixed constant under controlled conditions, demonstrating the potential of pulsed SP measurement as a facile method for evaluating the molecular weight of polyelectrolytes.

Abnormal glucose metabolism has been identified as a key characteristic of tumorigenesis. Visualizing the levels of monosaccharides in the lesion tissues and bodies of cancer patients is conducive to uncovering patterns of glucose metabolic reprogramming and assisting in the early diagnosis of cancer. Consequently, based on 7-(diethylamino)coumarin-3-carbohydrazide (DCCH), which has mass spectrometry/optical dual-signal enhancement functionality, both an on-tissue derivatization strategy suitable for matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) analysis and an in-solution derivatization strategy for capillary electrophoresis/laser-induced fluorescence (CE-LIF) analysis have been developed. During the on-tissue derivatization reaction, the nonvolatile MALDI matrix, 2,5-dihydroxybenzoic acid, was innovatively adopted as a proton donor. This approach not only efficiently catalyzes the derivatization process but also significantly minimizes analyte redistribution, and a low-cost airbrush application can achieve satisfying in situ derivatization. For further addressing the issue of the coexistence of multiple conformational isomers in biosamples, a rapid and efficient CE-LIF method was proposed for the separation of five DCCH-labeled monosaccharides (including three conformational isomers) within 8 min. By focusing on endometrial cancer (EC), the synergy of DCCH-mediated MALDI-MSI and CE-LIF analysis successfully achieved high-resolution in situ visualization of an obvious depletion difference in monosaccharides across the focal areas (tumor tissues, peritumoral tissues, and paracancerous tissues), and a comparative analysis was conducted on the serum monosaccharide profiles between patients with EC and those with benign uterine diseases. These analyses yielded novel molecular-level evidence, thereby facilitating a deeper understanding of the monosaccharide metabolic abnormalities associated with EC.

In response to the growing demand for advanced micro/nano characterization in materials and surface-interface sciences, we report a highly sensitive astigmatism displacement microscopy (ADM) system with subnanometer axial resolution of 0.1 nm. This low-power, noncontact, nondestructive, and rapid optical 3D imaging technique enables large-area characterization with exceptional imaging quality. Using ADM, we achieved high-quality 3D morphology characterization of Au nanoplates, CD-ROMs, semiconductor Si wafers, and few-layer 2D materials (like MoS₂). For few-layer 2D materials, ADM demonstrates a linear capability to resolve atomic layer numbers. Additionally, ADM successfully characterized transparent and semitransparent single crystals, even in the presence of inclination-induced interference fringes. The development of ADM provides a powerful tool for micro/nanoscale characterization, with significant implications for materials and surface-interface research.

Plasmonic nanolasers are proposed as one of the most promising tools in biosensing due to their high energy density, narrow spectral bandwidth, and feature sizes down to nanometers. However, the high threshold value greatly inhibits the widespread application of nanolasers. Researchers have made many efforts, among which the preparation of low-loss plasmonic nanocavities is the most fundamental approach. Herein, we used UV holographic lithography to prepare optical nanocavities with both a high quality factor (Q-factor) and strong resonance intensity (I), pairing with the LDS 751 dye as the gain material, to construct a plasmonic nanolaser with a record ultralow threshold of 0.49 mW/cm² at room temperature. Thus, we could display the first ultrasensitive DNA sensing of nanolaser in a biological environment by using a commercial laser pointer as the pumping source, achieving an ultralow detection limit of 1.91 nM for the Brucella genetic detection in serum. This work not only provides a universal strategy for constructing ultralow threshold nanolasers but also fully demonstrates the enormous advantages of nanolasers for biosensing.

Microfluidic-based in vitro physiological barrier models are capable of simulating crucial environmental factors during barrier formation, including fluid shear and geometric-level cellular cocultures, thus offering enhanced physiological fidelity relative to conventional platforms. However, the sealed structure of microfluidic barrier chips faces challenges in characterizing and monitoring the barrier performance, especially in measuring transendothelial/epithelial electrical resistance (TEER). Here, we developed a microfluidic barrier chip that can be easily adapted to commercial TEER detectors. During the barrier construction phase, continuous perfusion culture was utilized to maintain a constant fluid shear stress; for barrier characterization, commercial resistance meters were employed to measure TEER directly. Using this chip, we successfully constructed an in vitro blood-brain barrier model with a TEER of approximately 220 Ω·cm², indicating high physiological relevance. This scenario-adaptive microfluidic chip demonstrates extensive potential for developing organ-on-a-chip models across various barrier systems, with significant implications for barrier characteristic monitoring and in situ cell sampling within the chip.

Conventional solid-based SERS substrates often face challenges with inconsistent sample distribution, while liquid-based SERS substrates are prone to aggregation and precipitation, resulting in irreproducible signals in both cases. In this study, we tackled this dilemma by designing and synthesizing raspberry-like plasmonic nanoaggregates that exhibit a high density of hotspots and are colloidally stable at the same time. In particular, the nanoaggregates consist of a core made of functionalized polystyrene (PS) microspheres, which act as a template for rapid self-assembly of Au@Ag core-shell nanoparticles to form raspberry-like hierarchical nanoaggregates within 5 min of mixing. The optimized nanoaggregates can be used as reproducible and stable SERS substrates for a range of wastewater pollutants (e.g., rhodamine 6G (R6G) and malachite green (MG)) and nucleobases (e.g., adenine and uracil), with the detection limits as low as 1 × 10^-10, 1 × 10^-16, 3 × 10^-8, and 3 × 10^-7 M, respectively. Additionally, the trace detection of adenine in clinical urine samples has been successfully demonstrated. Our modular assembly approach opens up new possibilities in SERS substrate design and advanced trace-chemical detection technologies.