Aggregation of the natively unfolded protein αsynuclein (α-Syn) has been widely correlated to the neuronal death associated with Parkinson's disease. Mutations and protein overaccumulation can promote the aggregation of α-Syn into oligomers and fibrils. Recent work has suggested that α-Syn oligomers can permeabilize the neuronal membrane, promoting calcium influx and cell death. However, the mechanism of this permeabilization is still uncertain and has yet to be characterized in live cells. This work uses scanning ion conductance microscopy (SICM) to image, in real time and without using chemical probes, the topographies of live SH-SY5Y neuroblastoma cells after exposure to α-Syn oligomers. Substantial morphological changes were observed, with micrometer-scale hills and troughs observed at lower α-Syn concentrations (1.00 μM) and large, transient pores observed at higher α-Syn concentrations (6.0 μM). These findings suggest that α-Syn oligomers may permeabilize the neuronal membrane by destabilizing the lipid bilayer and opening transient pores.
Parkinson's disease (PD) is recognized as the second most common neurodegenerative disorder and has affected approximately one million people in the United States alone. A large body of evidence has suggested that deposition of aggregated alpha-synuclein (α-Syn), a brain protein abundant near presynaptic termini, in intracellular protein inclusions (Lewy bodies) results in neuronal cell damage and ultimately contributes to the progression of PD. However, the exact mechanism is still unclear. One hypothesis is that α-Syn aggregates disrupt the cell membrane's integrity, eventually leading to cell death. We used scanning ion conductance microscopy (SICM) to monitor the morphological changes of SH-SY5Y neuroblastoma cells and observed dramatic disruption of the cell membrane after adding α-Syn aggregates to the culturing media. This work demonstrates that SICM can be applied as a new approach to studying the cytotoxicity of α-Syn aggregates.
In
this work, surface-supportive MIL-88B(Fe) was explored as a
pH-stimuli thin film to release ibuprofen as a model drug. We used
surface plasmon resonance microscopy to study the pH-responsive behaviors
of MIL-88B(Fe) film in real time. A dissociation constant of (6.10
± 0.86) × 10–3 s–1 was
measured for the MIL-88B(Fe) film in an acidic condition (pH 6.3),
which is about 10 times higher than the dissociation of the same film
in a neutral pH condition. MIL-88B(Fe) films are also capable of loading
around 6.0 μg/cm2 of ibuprofen, which was measured
using a quartz crystal microbalance (QCM). Drug release profiles were
compared in both acidic and neutral pH conditions (pH 6.3 and 7.4)
using a QCM cell to model the drug release in healthy body systems
and those containing inflammatory tissues or cancerous tumors. It
was found that the amount of drug released in acidic environments
had been significantly higher compared to that in a neutral system
within 55 h of testing time. The pH-sensitive chemical bond breaking
between Fe3+ and the carboxylate ligands is the leading
cause of drug release in acidic conditions. This work exhibits the
potential of using MOF thin films as pH-triggered drug delivery systems.
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