This article discusses the use of a microfluidic acoustophoretic chip for the selective separation of Gram-negative and Gram-positive bacteria. The method utilizes acoustic waves to enhance the binding of specific bacteria to aptamer-coated microbeads, allowing for effective separation and analysis.
Take a microfluidic acoustophoretic chip, a sound-wave-based particle separator with two inlets and two outlets connected to plastic tubes.
Inject Gram-negative and Gram-positive bacteria, along with aptamer-coated microbeads, through the sample inlet.
Inject a buffer through the buffer inlet at high pressure to maintain side-by-side flow.
Inside the microchannel, the lipopolysaccharides on the Gram-negative bacterial membrane bind to the short single-stranded DNA aptamers on the microbeads.
Gram-positive bacteria, which lack lipopolysaccharides, do not bind.
As the flow continues, activate the piezoelectric transducer to generate acoustic waves that create pressure nodes across the channel.
These waves push large microbeads bound to Gram-negative bacteria toward the center, where they are collected at the target outlet.
Unbound small-sized Gram-positive bacteria remain unaffected and flow sideways to the waste outlet.
Microscopic imaging shows an increased signal from Gram-negative bacteria-bound beads at the target outlet, confirming their selective separation by aptamer-assisted acoustophoresis.
Connect PEEK tubes to the two inlets for injecting two samples and buffer, and the two outlets for collecting and discharging waste.
Using a 10 milliliter syringe, fill the microfluidic acoustophoresis channel with bubble free demineralized water. Prepare a precision pressure controller with two or more output channels to control the fluid flow. After preparing the device, inject the sample and buffer by applying a pressure of two kilopascals to the sample inlet and four kilopascals to the buffer inlet using the precision pressure control device.
Using a microscope, focus on a bead and move it to the center of the microfluidic channel using the PZT. Generate a resonance frequency of 3.66 megahertz using a single channel function generator and amplify a typical signal by 16 decibels using a power amplifier. Observe the separation and enrichment processes on the acoustofluidic chip with a fluorescence microscope and a high speed camera operating at 1, 200 frames per second.
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