"Stealth" dendrimers with encapsulation of indocyanine green for photothermal and photodynamic therapy of cancer

Poly(amido amine) dendrimers and indocyanine green have inevitable interaction with proteins and cells, which induces biological toxicity and reduces therapeutic efficacy in vivo. To overcome these shortcomings, a new drug delivery system G5MEK7C(n)-ICG with a "stealth" layer was prepared. The surface of G5MEK7C(n)-ICG was modified with double-layer super hydrophilic zwitterionic materials. In the "stealth" double-layer structure, the outer layer was consisted of zwitterionic Glu-Lys-Glu-Lys-Glu-Lys-Cys (EK7) peptide, and the inner layer was composed of amino and carboxyl groups with a ratio of 1:1. DLS results showed that the average hydrodynamic size of G5MEK7C(n)-ICG was about 25-30 nm, and the zeta potential was proven to undergo a slight charge reversal with the increasing pH values of solutions. Furthermore, G5MEK7C(n)-ICG exhibited excellent biocompatibility to red blood cells and proteins resistance. Photothermal and photodynamic experiments demonstrated that G5MEK7C(n)-ICG had a good photothermal conversion effect and generated singlet oxygen (¹O₂) under laser irradiation. The MTT and hemolysis results showed that the toxicity of G5 PAMAM was significantly reduced after modification double-layer structure. Cytotoxicity studies and flow cytometry showed G5MEK7C(70)-ICG under laser irradiation had a good effect on killing A549 cells. More importantly, the tumor inhibition rate of mice treated with G5MEK7C(70)-ICG (under laser irradiation) was 78.2% in vivo, which was higher than that of mice treated with free ICG. Compared with free ICG, G5MEK7C(70)-ICG caused less damage to the liver according to the enzyme activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Therefore, dendrimers modified with a zwitterionic double layer will be a promising candidate as a drug delivery system.

Inhibition of hIAPP Amyloid Aggregation and Pancreatic β-Cell Toxicity by OH-Terminated PAMAM Dendrimer

Human islet amyloid polypeptide (hIAPP, or amylin) forms amyloid deposits in the islets of Langerhans, a phenomenon that is associated with type-2 diabetes impacting millions of people worldwide. Accordingly, strategies against hIAPP aggregation are essential for the prevention and eventual treatment of the disease. Here, it is shown that generation-3 OH-terminated poly(amidoamine) dendrimer, a polymeric nanoparticle, can effectively halt the aggregation of hIAPP and shut down hIAPP toxicity in pancreatic MIN6 and NIT-1 cells as well as in mouse islets. This finding is supported by high-throughput dynamic light scattering experiment and thioflavin T assay, where the rapid evolution of hIAPP nucleation and elongation processes is halted by the addition of the dendrimer up to 8 h. Discrete molecular dynamics simulations further reveal that hIAPP residues bound strongly with the dendrimer near the c-terminal portion of the peptide, where the amyloidogenic sequence (residues 22-29) locates. Furthermore, simulations of hIAPP dimerization reveal that binding with the dendrimer significantly reduces formation of interpeptide contacts and hydrogen bonds, thereby prohibiting peptide self-association and amyloidosis. This study points to a promising nanomedicinal strategy for combating type-2 diabetes and may have broader implications for targeting neurological disorders whose distinct hallmark is also amyloid fibrillation.

PAMAM dendrimer based targeted nano-carrier for bio-imaging and therapeutic agents

In the last several decades, researchers have focused on developing suitable drug carriers to deliver pharmaceutical agents to treat cancer diseases.

Structure-function relationship of PAMAM dendrimers as robust oil dispersants

PAMAM dendrimers have recently been investigated as efficient and biocompatible oil dispersants utilizing their encapsulation capacity; however, their high cationic charge density has been shown to be cytotoxic. It is therefore imperative to mitigate cationic charge-induced toxicity and understand the effects of such changes. Presented here is a synergistic experimental and computational approach to examine the effects of varying terminal surface charge on the capacity of dendrimers to disperse model liner, polycyclic aromatic, and hybrid hydrocarbons. Uncharged dendrimers collapse by forming intramolecular hydrogen bonds, which reduce the hosting capability. On the other hand, changing the surface charges from positive to negative greatly shifts the pKa of tertiary amines of the PAMAM dendrimer interior. As a result, the negatively charged dendrimers have a significant percentage of tertiary amines protonated, ∼30%. This unexpected change in the interior protonation state causes electrostatic interactions with the anionic terminal groups, leading to contraction and a marked decrease in hydrocarbon hosting capacity. The present work highlights the robust nature of dendrimer oil dispersion and also illuminates potentially unintended or unanticipated effects of varying dendrimer surface chemistry on their encapsulation or hosting efficacy, which is important for their environmental, industrial, and biomedical applications.