Acid−base chemistry is central to a wide range of reactions. If students are able to understand how and why acid− base reactions occur, it should provide a basis for reasoning about a host of other reactions. Here, we report the development of a method to characterize student reasoning about acid−base reactions based on their description of what happens during the reaction, how it happens, and why it happens. We show that we can reliably place student responses into categories that reflect the model of acid−base reactivity used and whether the students invoke an electrostatic causal argument. However, the quality of student responses is highly dependent on the structure of the task prompt, which must be structured to provide students with enough information for them to understand what is needed. In general, students who construct responses that invoke a causal mechanistic Lewis model are more likely to draw appropriate curved arrow reaction mechanisms.

The study presented here is a follow-up to a previous report in which we investigated how general-chemistry students in a transformed curriculum reason about simple acid–base reactions. In the present study, we use and adapt the previously developed coding scheme for a longitudinal study in which we follow students from general chemistry through organic chemistry. We find that (i) generally, the manner in which students reason about acid–base reactions increases in sophistication over the course of a two-semester sequence of organic chemistry; (ii) there is little difference in reasoning between students at the end of a transformed general-chemistry course and a similar cohort at the beginning of organic chemistry; (iii) the nature of a student’s general-chemistry experience has a profound effect on the sophistication of their reasoning in that students from a transformed general-chemistry course are more likely to provide causal mechanistic explanations for simple acid–base reactions than students with other general-chemistry experiences; and (iv) the type of acid–base reaction that the students discuss impacts the type of reasoning they exhibit. We find that when asked to explain a Lewis acid–base reaction, students are less likely to invoke electrostatic ideas.

The development of a noninvasive method for the detection of Alzheimer's disease is of high current interest, which can be critical in early diagnosis and in guiding treatment of the disease. The aggregates of β-amyloid are a pathological hallmark of Alzheimer's disease. Carbohydrates such as gangliosides have been shown to play significant roles in initiation of amyloid aggregation. Herein, we report a biomimetic approach using superparamagnetic iron oxide glyconanoparticles to detect β-amyloid. The bindings of β-amyloid by the glyconanoparticles were demonstrated through several techniques including enzyme linked immunosorbent assay, gel electrophoresis, tyrosine fluorescence assay, and transmission electron microscopy. The superparamagnetic nature of the nanoparticles allowed easy detection of β-amyloid both in vitro and ex vivo by magnetic resonance imaging. Furthermore, the glyconanoparticles not only were nontoxic to SH-SY5Y neuroblastoma cells but also greatly reduced β-amyloid induced cytotoxicity to cells, highlighting the potential of these nanoparticles for detection and imaging of β-amyloid.

The accumulation and formation of β-amyloid (Aβ) plaques in the brain are distinctive pathological hallmarks of Alzheimer's disease (AD). Designing nanoparticle (NP) contrast agents capable of binding with Aβ highly selectively can potentially facilitate early detection of AD. However, a significant obstacle is the blood brain barrier (BBB), which can preclude the entrance of NPs into the brain for Aβ binding. In this work, bovine serum albumin (BSA) coated NPs are decorated with sialic acid (NP-BSA -Sia) to overcome the challenges in Aβ imaging in vivo. The NP-BSA -Sia is biocompatible with high magnetic relaxivities, suggesting that they are suitable contrast agents for magnetic resonance imaging (MRI). The NP-BSA -Sia binds with Aβ in a sialic acid dependent manner with high selectivities toward Aβ deposited on brains and cross the BBB in an in vitro model. The abilities of these NPs to detect Aβ in vivo in human AD transgenic mice by MRI are evaluated without the need to coinject mannitol to increase BBB permeability. T *-weighted MRI shows that Aβ plaques in mouse brains can be detected as aided by NP-BSA -Sia, which is confirmed by histological analysis. Thus, NP-BSA -Sia is a promising new tool for noninvasive in vivo detection of Aβ plaques.