Nanoparticle Targeting to Neurons in a Rat Hippocampal Slice Culture Model

Abstract

We have previously shown that CdSe/ZnS core/shell luminescent semiconductor nanocrystals or QDs (quantum dots) coated with PEG [poly(ethylene glycol)]-appended DHLA (dihydrolipoic acid) can bind AcWG(Pal)VKIKKP9GGH6 (Palm1) through the histidine residues. The coating on the QD provides colloidal stability and this peptide complex uniquely allows the QDs to be taken up by cultured cells and readily exit the endosome into the soma. We now show that use of a polyampholyte coating [in which the neutral PEG is replaced by the negatively heterocharged CL4 (compact ligand)], results in the specific targeting of the palmitoylated peptide to neurons in mature rat hippocampal slice cultures. There was no noticeable uptake by astrocytes, oligodendrocytes or microglia (identified by immunocytochemistry), demonstrating neuronal specificity to the overall negatively charged CL4 coating. In addition, EM (electron microscopy) images confirm the endosomal egress ability of the Palm1 peptide by showing a much more disperse cytosolic distribution of the CL4 QDs conjugated to Palm1 compared with CL4 QDs alone. This suggests a novel and robust way of delivering neurotherapeutics to neurons.

Measuring brain lipids

“…The Zn on the surface of the QD can be used to bind cargo by attaching polyhistidine (HIS 6 ) to the C or N-terminal end of the peptide/protein/drug. This binding is quite tight (72h in cultured cells, longer in brain) and QDs can release the cargo in vivo over a period of >15 days in chick brains [63]. The incorporation of a cell-penetrating peptide (JB577) (WGDapVKIKK), a non-hydrolysable analog of palmitoylated K-Ras 4A, into the construct allows release of the cargo from the endosome (a huge problem for other types of drug/protein delivery) and potentially promotes penetration of the blood brain barrier of the therapeutic you are trying to deliver (61).…”

“…The particles are also electron-dense enough that we can use electron microscopy to determine subcellular localization (62,63). A major problem with current therapies is that microglia (or macrophages) are likely to sequester a major portion of any cargo but we can prevent this by using zwitterionic or negatively charged coats (CL4) to specifically target the cargo (enzyme) to neurons rather than glia [63]. We have also discovered that by digesting away the extracellular matrix surrounding glial cells we can promote uptake by oligodendrocytes and hopefully induce remyelination.…”

Enhancing enzymatic efficiency by attachment to semiconductor nanoparticles for biosensor applications

“…[20] QDs functionalize with these ligands have already proven themselves in a variety of challenging environments. [21][22][23] …”

Nanoparticles for Brain-Specific Drug and Genetic Material delivery, Imaging and Diagnosis

“…Endosomal escape is a key factor for nanoparticle-induced efficient transfection and conjugation of QDs, with some peptides, like those derived from the parent peptide JB577, not only mediating cytosolic delivery in brain tissue but also facilitating efficient endosomal escape [87]. Similarly, conjugation of QDs with PEG-appended dyhydrolipoic acid (DHLA) and linked to the peptide Palm1 allowed the QDs to be taken up by different culture cells and readily escape the endosome to the soma [88].…”