Zn(ii)-Dipicolylamine analogues with amphiphilic side chains endow low molecular weight PEI with high transfection performance

To investigate the effect of amphiphilic balance of Zn(ii)-dipicolylamine analogues on the transfection process, we fabricated a series of Zn(ii)-dipicolylamine functional modules (DDAC-Rs) with different hydrophilic-phobic side chains to modify low molecular weight PEI (Zn-DP-Rs) by the Michael addition reaction. Zn-DP-Rs with hydrophilic terminal hydroxy group side chains demonstrate superior overall performance compared to those of hydrophobic alkyl side chains. In terms of the influence of the chain lengths in DDAC-Rs, from Zn-DP-A/OH-3 to Zn-DP-A/OH-5, the corresponding transfection efficiency shows an upward trend as the lengths increase. However, decreasing efficacy is observed with further increase in the length of side chains. In addition, the Zn-DP-Rs with amphiphilic side chains show prominent performance in every respect, highlighting the significance of balance in the amphipathy of side chains in DDAC-Rs. This work is of great significance for the development of polycationic gene carrier materials with excellent performance.

Nanocarriers for delivery of siRNA and co-delivery of siRNA and other therapeutic agents

A major problem in cancer treatment is the multidrug resistance. siRNA inhibitors have great advantages to solve the problem, if the bottleneck of their delivery could be well addressed by the various nanocarriers. Moreover, co-delivery of siRNA together with the various anticancer agents in one nanocarrier may maximize their additive or synergistic effect. This review provides a comprehensive summary on the state-of-the-art of the nanocarriers, which may include prodrugs, micelles, liposomes, dendrimers, nanohydrogels, solid lipid nanoparticles, nanoparticles of biodegradable polymers and nucleic acid nanocarriers for delivery of siRNA and co-delivery of siRNA together with anticancer agents with focus on synthesis of the nanocarrier materials, design and characterization, in vitro and in vivo evaluation, and prospect and challenges of nanocarriers.

Computationally efficient methodology for atomic-level characterization of dendrimer-drug complexes: a comparison of amine- and acetyl-terminated PAMAM

PAMAM dendrimers have been widely studied as a novel means for controlled drug delivery; however, computational study of dendrimer-drug complexation is made difficult by the conformational flexibility of dendrimers and the nonspecific nature of the dendrimer-drug interactions. Conventional protocols for studying drug binding have been designed primarily for protein substrates, and, therefore, there is a need to establish new protocols to deal with the unique aspects of dendrimers. In this work, we generate cavities in generation-5 polyamidoamine (PAMAM) dendrimers at selected distances from the center of mass of the dendrimer for the insertion of the model drug: dexamethasone 21-phosphate or Dp21. The complexes are then allowed to equilibrate with distance between centers of mass of the drug and dendrimers confined to selected ranges; the free energy of complexation is estimated by the MM-GBSA (MM, molecular mechanics; GB, generalized Born; SA, surface area) method. For both amine- and modified acetyl-terminated PAMAM at both low and neutral pH, the most favorable free energy of complexation is associated with Dp21 at distance of 15-20 Å from the center of mass of the dendrimer and that smaller or larger distances yield considerably weaker affinity. In agreement with experimental results, we find acetyl-terminated PAMAM at neutral pH to form the least stable complex with Dp21. The greatest affinity is seen in the case of acetyl-terminated PAMAM at low pH, which appears to be due a complex balance of different contributions, which cannot be attributed to electrostatics, van der Waals interactions, hydrogen bonds, or charge-charge interactions alone.