BBB Transporter Assay

Neuropharmaceuticals are the largest potential growth sector in the pharmaceutical industry. However, this growth has been hindered by blood-brain barrier (BBB) problems. To better meet the demands of future brain drug development programs, Creative Biolabs offers our customers around the world with comprehensive, reliable, and cutting-edge BBB transporter assay.

Blood-Brain Barrier and BBB Transporter

The anatomical basis of the BBB is the brain microvascular endothelial cell barrier, which can prevent 100% of macromolecular drugs and >98% of small molecule drugs from entering the brain. Unless changes are made, future development of CNS drugs will be limited to lipid-soluble small molecule drugs that cross the BBB via lipid-mediated free diffusion. The BBB can be traversed, and with a better understanding of endogenous BBB transporters on capillary endothelial cells, new drugs with designed structures can enter the brain via endogenous BBB transporters.

Endogenous BBB transporters can be divided into three categories, Carrier-mediated transporter (CMT), Active efflux transporter (AET), and Receptor-mediated transporter (RMT). CMT and AET are responsible for the transport of small molecules between blood and brain, while the RMT system is responsible for mediating the transport of endogenous macromolecules across the blood-brain barrier. The CMT is responsible for both inflow and outflow of the BBB, while the AET system typically mediates the efflux of brain to blood substrates.

Fig 1. Schematic drawing of transport routes across the BBB. (Juhairiyah, 2021)

Carrier-mediated Transport

CMT transporters tend to belong to the SLC superfamily and regulate the flow of solutes into or out of cells. Currently well-studied and cloned CMT transporters include single-intermediate transport systems for choline and thiamine through the family of organic cation transporters, cationic amino acid transporters for L-lysine/arginine/ornithine, neutral amino acid transporter for neutral amino acids and some drugs, hexose transport system for glucose and mannose, as well as monocarboxylic acid transport system, medium chain fatty acid transport system, peptide transport system, etc. Various CMT systems provide a diverse molecular structure space. For this type of transport system, Creative Biolabs performs screening, cloning, or overexpression/knockout operations according to different experimental needs. At the same time, we also chemically modify existing drugs to mimic the transport cargo, allowing selected chemical molecules to cross the BBB.

Fig 2. Modeled structure of GLUT1. (Barar, 2016)

Active Efflux Transport

AET transport systems for small molecules belong to one of two protein superfamilies, the ATP-Binding Cassette (ABC) or the solute carrier (SLC) transporter. Members of the SLC family typically include OAT or OATP organic anion transporters, tonic taurine transporters, acidic amino acid transporters, etc. These transporters work together to regulate the active efflux of specific drugs and molecules. ABC's function directly depends on energy. The ABC superfamily includes seven families and 48 different transporters. Among them, the most concerned and critical efflux transporter is P-glycoprotein (MDR1 and MDR3). For AET transporters, Creative Biolabs provides screening of various small-molecule drugs and compounds including antibiotics, antihistamines, calcium channel blockers, analgesics, cloning and characterization of transporters, or on-demand overexpression/knockout.

Fig 3. ABC transporters at the BBB. (Nilles, 2022)

Receptor-mediated Transport

Cellular trafficking of macromolecular biomolecules is mediated through the membrane-vesicle mechanism. On the BBB, as many as twenty receptors have been confirmed to have the ability to initiate receptor-mediated cellular transport, including scavenger receptor, tumor necrosis factor, insulin/insulin-like growth factor receptor, lipoprotein E receptor, leptin receptor, LDL receptor, EGF receptor, melanotransferrin receptor, etc. Mediating the transport of macromolecular drugs through the RMT system is the main research direction of drug development in the central nervous system. With our professional and comprehensive technology platform, Creative Biolabs can clone and characterize the receptors you are interested in, provide cell models that stably express the receptor, or modify and screen drugs as needed.

Fig 4. 3D structure of the complex of TfR1 and human insulin receptor. (Pardridge, 2022)

Our Service

As a leader in neurological disease and molecular biology research, Creative Biolabs has accumulated and explored target information and knowledge for drug delivery in the central nervous system that can be used to improve neuroprotective drug development. In addition to BBB transporter clones, we also characterize the specific information and enrichment of your transporter of interest by immunoblotting, in situ hybridization and staining techniques. Whether it is the isolation of experimental animal tissues, the enrichment of BBB endothelial cells, the identification and quantification of BBB proteins or the pharmacokinetic analysis of specific molecules, you can trust our professional team. We also provide in vitro BBB models with extremely high fidelity, and reformulate drug structures based on knowledge of endogenous BBB transporters, providing the most reliable service for your brain drug development or BBB transporter basic research. Please do not hesitate to contact us for more information.

References

1. Juhairiyah, F.; et al. Understanding drug delivery to the brain using liposome-based strategies: studies that provide mechanistic insights are essential. The APPS Journal. 2021, 23: 114.
2. Barar, J.; et al. Blood-brain barrier transport machineries and targeted therapy of brain diseases. Bioimpacts. 2016, 6(4): 225-246.
3. Nilles, K.L.; et al. Blood-brain barrier transporters: opportunities for therapeutic development in ischemic stroke. International Journal of Molecular Sciences. 2022, 23: 1898.
4. Pardridge, W.M. Kinetics of blood-brain barrier transport of monoclonal antibodies targeting the insulin receptor and the transferrin receptor. Pharmaceuticals. 2022, 15: 3.