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Nishanthan srikantha, Timothy L. Jackson, Klaus Suhling, James Levitt; Translational Diffusion Of Ranibizumab As Measured By Fluorescence Recovery After Photobleaching (frap). Invest. Ophthalmol. Vis. Sci. 2011;52(14):2325.
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Previous research by the group has shown a retinal molecular weight exclusion limit of 60,000 Dalton across the retina. It is thought that the 149,000 Dalton bevacizumab and 48,000 Dalton ranibizumab have similar therapeutic effects through clinical experience and small studies. It would be anticipated that ranibizumab is more effective as its lower molecular weight should facilitate diffusion across the retina.
We studied the diffusion properties of ranibizumab using FRAP (Fluorescence Recovery after Photobleaching), to measure the translational diffusion of fluorescently labeled ranibizumab. The translational diffusion coefficient was used to calculate an approximate size for ranibizumab.
It appears ranibizumab has a molecular radius of 5.5nm based on its translational diffusion characteristic. Preliminary results indicate this radius predicts the molecular weight to be much larger than the documented 48,000 Dalton.
Our results demonstrate ranibizumab to hold diffusion characteristics of a molecule with a higher molecular weight than expected. This may partly explain the reported similarity in the therapeutic effect of bevacizumab and ranibizumab although further studies are needed to validate this preliminary findings.
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