Title : Development of a Targeted Drug Delivery System for the CNS using a Novel In Vitro Blood Brain Barrier Model
Efficient delivery of therapeutics to the central nervous system (CNS) is extensively limited by the blood brain barrier (BBB).Cell penetrating peptides (CPP) have gained recognition for enhancing the uptake of conjugated payloads into various cell types, however, the non-specific manner of cellular uptake is not suitable for toxic or expensive drugs such as proteinaceous growth factors.Nanoparticles, depending on their chemical composition, can be formulated to entrap a variety of drugs within their core, releasing their payload over a time period. For biological applications, nanoparticles composed of poly(D,L-lactide-co-glycolide) (PLGA) can be surface modified with a targeting peptide to facilitate specific delivery of a therapeutic payload to certain areas of the body, achieving controlled and targeted delivery.
Rabies virus-derived peptide (RDP) has shown promise as a targeting peptide for drug delivery to the brain.This derivative of rabies virus glycoprotein (RVG) may potentially facilitate drug targeting to the CNS for the treatment of neurodegenerative disorders such as Parkinson’s disease.Previously, we have shown that RDP action in SH-SY5Y neuroblastoma cells is dependent on the nicotinic acetylcholine receptor (nAChR). However, due to the size of RDP (39 residues) it may be prone to proteolytic degradation in vivo thereby limiting its targeting capabilities.
In light of this, we subsequently modelled a new peptide on the RDP/nAChR interaction and designed a novel targeting ligand, which we termed DAS. The serum stability and neural cell-specific targeting properties of the novel RDP-derivative, DAS, were investigated to assess its potential as a neural cell- targeting ligand. DAS peptide demonstrated greatly enhanced serum stability in vitro compared to RDP. Furthermore, DAS-labelled PLGA nanoparticles (with a drug payload) demonstrated neural cell-specific targeting abilities.
To investigate the ability of this new peptide to carry a conjugated payload into the CNS, we have developed a human cell line in vitro BBB model. This triple-layer co-culture composed of brain microvascular endothelial cells, pericytes and astrocytes exhibited both excellent in vitro TEER values and expression levels of ZO-1 and claudin-5 tight junction proteins, all measures of BBB integrity. Our results clearly demonstrate that DAS can effectively and efficiently deliver conjugated drug-loaded NP across a BBB model and release drug payload on the basolateral (brain) side of the model. TEER values were unaffected by targeted drug delivery signifying that BBB integrity was not compromised by the new targeted delivery system. Although inter-species BBB models have been used previously in drug transport studies, it is advantageous to have an all human-derived model. The differences between interspecies BBB cells is not well known and use of human cells may more accurately predict human in vivo responses to drugs and their delivery vehicles.
RDP derivatives such as DAS may prove beneficial in the pursuit of effective regenerative treatments for various neurodegenerative diseases such as Parkinson’s disease, providing a means of targeted delivery for new therapeutics with curative potential by providing a means of overcoming the restrictions of the BBB.
Audience take away:
- We have developed a human-derived BBB model that can be used for drug transport studies.
- This model can be used to develop lead compounds before expensive animal models are employed.
- This model can be used for the development of therapeutics for a range of neurodegenerative disorders.
- These targeted nanoparticles can be loaded with a range of compounds including growth factors and antibody-based drugs that normally demonstrate difficulty in overcoming the BBB.