Delivering And Tracking Drugs With Nanoparticles

A nontoxic nanoparticle developed by researchers in the US could be an effective delivery system for both therapeutic drugs and conjugate ser in present tense fluorescent dyes that track their delivery. The interdisciplinary group of materials scientists, chemists, bioengineers, physicists and pharmacologists showed that calcium phosphate particles ranging in size from 20 to 50 nm can successfully enter cells and dissolve harmlessly, releasing their cargo of drugs or dye.

The calcium phosphate nanoparticles were developed by James Adair, Professor of materials science and engineering at Pennsylvania State University (PA, USA), and his students. The nanoparticles have several benefits other drug delivery systems do not, according to the Lead Author of the study, Thomas Morgan, who is a graduate in chemistry.

Unlike quantum dots that are composed of toxic metals, calcium phosphate is a safe, naturally occurring mineral that is already present in substantial amounts in the bloodstream.

'What distinguishes our method are smaller particles (for uptake into cells), no agglomeration (particles are dispersed evenly in solution), and that we put drugs or dyes inside the particle where they are protected, rather than on the surface,' says Morgan. 'For reasons we don't yet understand, fluorescent dyes encapsulated within our nanoparticles are four times brighter than free dyes.

'Drugs and dyes are expensive,' he continues, 'but an advantage of encapsulation is that you need much less of them. We can make high concentrations in the laboratory, and dilute them way down and still be effective. We even believe we can combine drug and dye delivery for simultaneous tracking and wedding present gigs treatment. That's one of the things we are currently working on.'

Peter Butler, Associate Professor of bioengineering at Pennsylvania State University, and present on admission coding his students used high-speed lasers to measure the size of fluorescent dye-containing particles from their diffusion in solution. Butler says: 'We use a technique called time correlated single photon counting. This uses pulses of laser light to read the time, on the order of nanoseconds, that molecules fluoresce.'

Using this method, his group measured the size of the particles and their dispersion in solution in this case a phosphate-buffered saline that is used as a simple model for blood.

'What we did in this study was to change the original neutral pH of the solution, which is similar to blood, to a more acidic environment, such as around solid tumours and in the parts of the cell that collect the nanoparticles-containing fluid immediately outside the cell membranebring it into the cell. When we lower the pH, the acidic environment dissolves the calcium phosphate particle,' says Butler. 'We can see that the size of the particles becomes very small, essentially down to the size of the free dye that was inside the particles. That gives us evidence that this pH change can be used as a mechanism to release any drug that is encapsulated in the particle.'

Although the primary use envisioned for these particles is for targeted cancer therapy, Butler's group is interested in their ability to deliver various drugs that have been shown to inhibit cell growth associated with vascular disease.

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