Histochemical targeting: Combining plasma immersion ion implantation and histochemical probes to target magnetic particles to intracellular cytological features

Abstract

Paramagnetic microparticles are effective tools for cell purification, diagnostics, imaging and drug delivery and have been used for over 30 years to separate cell types from complex mixtures. The targeting of magnetic particles to cells and tissues is dependent upon the use of antibodies and adhesion molecules as targeting modalities. Here, we present a novel paradigm for the targeting of microparticles to cells according to intracellular cytological characteristics. Cell-permeable histochemical dyes, when covalently conjugated to magnetic microparticles, following plasma immersion ion implantation (PIII) imbue the particles with cell targeting properties in a process we term histochemical targeting. PIII treatment and conjugation to the lipophilic dyes Nile Red or Nile Blue led to changes in microparticle size, surface charge and lipophilicity. PIII-treated microparticles covalently conjugated with Nile Red, crossed the live cell membrane and homed to intracellular neutral lipid droplets. Nile Blue-conjugated particles crossed live cell membranes and remained in the cytosol where free fatty acids localize. Magnetic cell sorting could be performed on cultured adipocytes, as well as rat liver and adrenal cell suspensions using particles conjugated to Nile Red or Nile Blue. Taken together, our findings demonstrate that histochemical probes can be covalently conjugated to magnetic particles following PIII treatment resulting in intracellular targeting. With a vast armamentarium of cell-permeable probes available, histochemical targeting could be applied to many fields requiring magnetic particle delivery to specific sites or isolation of particular cell types.

Keywords

• Histochemical dyes
• Probes
• Magnetic particles
• Plasma treatment
• Cell targeting