Methods and compositions for monitoring cellular membranes or cellular membrane coated nanoparticles

A method for monitoring a cellular membrane coated nanoparticle after in vivo administration, which method comprises:

• a) obtaining a sample from a subject to which has been administered a cellular membrane coated nanoparticle, said nanoparticle comprising an inner core comprising a non-cellular material and an outer surface comprising a cellular membrane derived from a cell;
• and
• b) assessing the presence, absence, amount and/or level of a biomarker from cellular membrane of said cellular membrane coated nanoparticle in said sample, said biomarker having a base level in said sample that is below a threshold level, and
• wherein said biomarker is Band 3 protein, or a fragment thereof, and a ratio between said level of said biomarker in said sample obtained from said subject to which has been administered said nanoparticle and said base level of said biomarker in said sample is at least 2, and
• said method has an assay linearity ranging from 100 pg Band 3 protein/ml sample to 100 ng Band 3 protein/ml sample, a relative standard deviation (RSD) of 30% or less, and a limit of detection (LOD) of Band 3 protein at about 50 pg or 100 pg Band 3 protein/ml sample.