Activated Microglia Targeting Dendrimer–Minocycline Conjugate as Therapeutics for Neuroinflammation

Abstract

Brain-related disorders have outmatched cancer and cardiovascular diseases worldwide as the leading cause of morbidity and mortality. The lack of effective therapies and the relatively dry central nervous system (CNS) drug pipeline pose formidable challenge. Superior, targeted delivery of current clinically approved drugs may offer significant potential. Minocycline has shown promise for the treatment of neurological diseases owing to its ability to penetrate the blood–brain barrier (BBB) and potency. Despite its potential in the clinic and in preclinical models, the high doses needed to affect a positive therapeutic response have led to side effects. Targeted delivery of minocycline to the injured site and injured cells in the brain can be highly beneficial. Systemically administered hydroxyl poly(amidoamine) (PAMAM) generation-6 (G6) dendrimers have a longer blood circulation time and have been shown to cross the impaired BBB. We have successfully prepared and characterized the in vitro efficacy and in vivo targeting ability of hydroxyl-G6 PAMAM dendrimer–9-amino-minocycline conjugate (D-mino). Minocycline is a challenging drug to carry out chemical transformations due to its inherent instability. We used a combination of a highly efficient and mild copper catalyzed azide–alkyne click reaction (CuAAC) along with microwave energy to conjugate 9-amino-minocycline (mino) to the dendrimer surface via enzyme responsive linkages. D-mino was further evaluated for anti-inflammatory and antioxidant activity in lipopolysaccharides-activated murine microglial cells. D-mino conjugates enhanced the intracellular availability of the drug due to their rapid uptake, suppressed inflammatory cytokine tumor necrosis factor α (TNF-α) production, and reduced oxidative stress by suppressing nitric oxide production, all significantly better than the free drug. Fluorescently labeled dendrimer conjugate (Cy5–D-mino) was systematically administered (intravenous, 55 mg/kg) on postnatal day 1 to rabbit kits with a clinically relevant phenotype of cerebral palsy. The in vivo imaging study indicates that Cy5–D-mino crossed the impaired blood–brain barrier and co-localized with activated microglia at the periventricular white matter areas, including the corpus callosum and the angle of the lateral ventricle, with significant implications for positive therapeutic outcomes. The enhanced efficacy of D-mino, when combined with the inherent neuroinflammation-targeting capability of the PAMAM dendrimers, may provide new opportunities for targeted drug delivery to treat neurological disorders.

Scalable synthesis and validation of PAMAM dendrimer‐N‐acetyl cysteine conjugate for potential translation

“…Dendrimers are structurally "monodisperse" with well-defined building blocks and surface functionality, and have garnered significant attention as promising scaffolds for various biomedical applications including drug/gene delivery, targeting, imaging and diagnosis due to their unique physico-chemical properties. [19][20][21][22][23][24][25] These multivalent nanostructures can be tuned conveniently to incorporate various molecules of interest.…”

Dense hydroxyl polyethylene glycol dendrimer targets activated glia in multiple CNS disorders

“…The selective uptake of PEGOL-60 in the injured brain regions of CP animals could be explained because of its ability (i) to cross the impaired BBB, (ii) to diffuse efficiently within the brain parenchyma due to its neutral charge, and (iii) to be picked up by phagocytic activated Mi/Ma. On the basis of our previous experience with PAMAM dendrimer-drug conjugates (12,13), we envision that the drug loading capacity of PEGOL-60 should be ~20 weight % (wt %) for the dendrimer targeting properties to be conserved.…”

“…In addition to the ability to target key cells in the CNS, additional supplementary criteria include safety profile, water solubility, synthetic reproducibility, and feasibility for large-scale production toward successful commercialization. Dendrimers have shown potential in diverse biomedical applications including but not limited to targeted drug/gene delivery, diagnosis, and imaging (11)(12)(13)(14)(15). Dendrimers are three-dimensional, hyperbranched, monodisperse, globular nanoparticles whose surface groups, size, and molecular composition can be manipulated precisely during their preparation for desired biomedical applications.…”

Genetic effects of welding fumes on the progression of neurodegenerative diseases

“…NDGDs are a collective term for a heterogeneous group of disorders that are incurable and characterized by the progressive degeneration of the function and structure of the central nervous system [5]. NDGDs primarily affect the neurons of the central nervous system and progressively damage their function.…”