Table 1 Novel strategies and various popular transport models to deliver therapeutic drugs through the BBB
Novel strategies | Route | Merits | Demerits | Drugs/molecules | References |
|---|---|---|---|---|---|
Osmotic disruption | Paracellular | • Transient • Alters barrier-inducing factors • Promising delivery for recombinant vectors | • Invasive • Transient cerebral edema • Non-specific | • Anticancer drugs • Cytotoxic drugs • Adenoviral vectors | |
Chemical disruption | Paracellular | • Transient • Site-specific drug delivery | Conflicting results in clinical trials | • Neuropeptides • Neurotransmitter • Antibiotics • Antineoplastic agents | |
Biochemical disruption | Non-invasive | Selective opening of brain tumor capillaries | Breaks down the self-defense mechanism | • Intracarotid infusion of leukotriene C4 | [192] |
Evade active efflux | transcellular | Involved in multidrug resistance | Restricts the drug distribution | • Phenothiazines • Inhibitors of serotonin re-uptake | [193] |
Tight junction pathways | Paracellular (diffusion) | A high capacity pore pathway | Require novel high resolution techniques to detect single openings and closings | Activation of apical sodium-glucose cotransport (SGLT1) | [193] |
Nanoparticle delivery | Paracellular (diffusion) and Transcellular (transcytosis) | • Targeted • Sustained and/or regulated release | • Expensive • High toxicity • Clinical efficacy undemonstrated | Liposomal doxorubicin, temozolomide | |
Biodegradable polymer | Encircle BBB | • Controlled drug delivery | • Useful for limited patients | [164] | |
Pro-drug | • High drug residence time • Specific membrane transporter | • Low selectivity • Low retention • Toxicity | • Fatty acids, glyceride or phospholipids • Precursor ofGABA, • Niflumic acid • Valproate or vigabatrin | ||
Biological tissue delivery | Invasive | • Co-grafted cells release therapeutic proteins | • Inefficient transfection • Non-selective expression • Deleterious regulation | Intracarotid infusion of leukotrienes, bradykinin | [169] |
Vasoactive peptides | Transient | Non-invasive | • Poor clinical efficacy | RMP-7/ labradimil/Cereport | |
Cell-mediated endocytosis | Transcellular | Targeted | • Toxic for cell carrier system • Less therapeutic loading | • TAT • Penetratin • polyarginines | |
Focused ultrasound | Paracellular and Transcellular (diffusion and convection) | • Non-invasive • Targeted | Costly | • Antibodies, doxorubicin • Carboplatin | |
Radiation | Paracellular and Transcellular | • Increases permeability | Radiation-induced (Neuro) inflammation | Insulin | |
Intrathecal and intraventricular delivery | Bypass BBB | • Encounter minimized protein binding • Decrease enzymatic activity • Longer drug shelf-life | • Invasive • Low parenchymal concentrations • Prompt CSF turnover • High clinical incidence of hemorrhage • Neurotoxicity | Recombinant human heparin-N-sulfatase (rhHNS) | |
Olfactory pathway | Crosses BBB | • Non-invasive • Simple drug administration | • Discomfort nasal mucosa • Lower efficiency | Neurotropic factor | [209] |
Interstitial wafers, microchips and nanospheres | Crosses BBB | • Sustained and controlled release • Easily implantable without damage | • Invasive • Distribution is limited through ECS | ||
Convection- Enhanced Delivery (Injections, Catheters and Pumps) | Bypass BBB Through transcellular | • Enhances distribution by bulk flow | • Invasive • backflow of infusate • catheter misplacement risk • Expensive • Low efficiency | • Gadolinium • Magnetic nanoparticles | |
Carrier-mediated | Transcellular (transcytosis) Non-invasive | Controls the delivery and retention of drugs | A highly stereospecific drug is converted to structure similar to that of endogenous nutrient | Levodopa • Melphaling • Glucose | [213] |
Receptor-mediated | Transcellular (transcytosis) | • Allows planned transport linkers to suit the characterized functional requirement of the therapeutic agent, including peptide-based pharmaceuticals and small molecules incorporated within liposomes • These transporters can be examined for brain delivery | Saturable process, enzymatic drug release, attachment to a BBB transport vector depicts certain drugs inactive | • Transferrin receptor • Lactoferrin receptor • Insulin receptor | |
Adsorptive mediated | Transcytosis | • Uses a cationic biological macromolecule | • Cationized bovine serum albumin (BSA) • Cationized immunoglobulins/monoclonal antibodies (Mabs) |