Controllable Self-Assembly of Amphiphilic Dendrimers on a Silica Surface: The Effect of Molecular Topological Structure and Salinity

Analysis of dendrimer-protein interactions and their implications on potential applications of dendrimers in nanomedicine

This work addresses how G5.5 PAMAM dendrimers form complexes with bovine serum albumin (BSA). Analytical techniques, such as UV-vis spectrophotometry, dynamic light scattering, electrophoretic mobility, quartz crystal microbalance with dissipation monitoring (QCM-D), circular dichroism (CD), and contact angle were used to analyze the properties of the dendrimers systems. The binding of protein to dendrimers can alter the structure, mobility, conformation and functional activity of the dendrimer. The results show that BSA interactions with G5.5 dendrimer carriers are driven both by electrostatic and hydrophobic forces. Dendrimer surface charge is reduced upon contact with the protein. The protein shell formed on the surface of the carrier is very stable as evidenced by the QCM-D measurements. On the other hand, the CD spectra indicates a change in the secondary structure of the protein. The size of the changes is significantly dependent on the ratio of protein to dendrimer. Understanding the mechanism of interaction of potential carriers with proteins is important for their internalization into the cell.

Dual-Responsive Nanotubes Assembled by Amphiphilic Dendrimers: Controlled Release and Crosslinking

Although stimuli-responsive release systems have attracted great attention in medical applications, there has been no attempt at “precise” deep profile control based on such systems, which is greatly need to improve oil recovery. With this in mind, we provided a facile and simple strategy to prepare stimuli-responsive composite capsules of amphiphilic dendrimers–poly(styrene sulfonic acid) sodium/halloysite nanotubes (HNTs) via layer-by-layer (LbL) self-assembly technique, controlling the release crosslinking agent methenamine under different pH or salinity conditions. The release time of methenamine encapsulated in multilayer shells is about 40 h, which can be prolonged with the introduction of salt or shortened via the addition of acid, which accordingly induces the gelation of polyacrylamide (PAM) solutions, taking from a few hours to a dozen days. This study provided a novel approach for controllable release of chemical agents and controllable crosslinking of deep profiles in many application fields.

Self-Assembly and Functions of Star-Shaped Oligomeric Surfactants

Oligomeric surfactants consist of three or more amphiphilic moieties which are connected by spacer groups covalently at the level of headgroups. It provides a possible route to bridge the gap from conventional single-chain surfactants to polymeric surfactants and leads to many profound improvements in the properties of surfactants in aqueous solution and at the air/water and water/solid interfaces. Generally, oligomeric surfactants are categorized into linear, ring-like, and star-shaped on the basis of the topological structures of their spacer groups, and their aggregation behavior strongly depends on the resultant topological structures. In recent years, we studied trimeric, tetrameric, and hexameric surfactants with a star-shaped spacer which spreads from a central site of elemental nitrogen or carbon, and their charged headgroups connect with each other through the spacers. It has been found that both the nature of spacer groups and the degree of oligomerization show important influences on the self-assembly of oligomeric surfactants and provide great possibilities in fabricating various surfactant aggregate morphologies by adjusting the molecule conformations. The unique self-assembly behavior endows them with superior physicochemical properties and potential applications. This feature article summarizes the development of star-shaped oligomeric surfactants, including self-assembly at the air/water and water/solid interfaces, self-assembly in aqueous solution, and their functions. We expect that this review could provide a comprehensive understanding of the structure-property relationship and various potential applications of star-shaped oligomeric surfactants and offer additional motivation for their future research.

PAMAM-Based Dendrimers with Different Alkyl Chains Self-Assemble on Silica Surfaces: Controllable Layer Structure and Molecular Aggregation

Amphiphilic poly(amidoamine) (PAMAM) dendrimers are a well-known dendritic family due to their remarkable ability to self-assemble on solid surface. However, the relationship between molecular conformation (or adsorption kinetics) of a self-assembled layer and molecular amphiphilicity of such kind of dendrimer is still lacking, which limits the development of modulating self-assembling structures and surface functionality. With this in mind, we synthesized a series of amphiphilic PAMAM-based dendrimers, denoted as G₁C _n, with different alkyl chains ( n = 8, 12, and 16), and investigated the molecular aggregation on silica surfaces by means of quartz crystal microbalance with dissipation, atomic force microscopy, and contact angle. After rinsing, remaining adsorption amounts of G₁C₁₂ were higher than those of G₁C₈ at high concentrations, suggesting that G₁C₁₂ adlayers were more stable due to the stronger intermolecular hydrophobic interactions, whereas it preferred to adopt the intramolecular hydrophobic interactions for G₁C₁₆, with low adsorption amounts and unstable adlayers. Bilayer-like structures were inferred in G₁C₈ and G₁C₁₂ adlayers with loose conformation, whereas monolayer structures were likely to exist in the sparse adsorption film of G₁C₁₆. Our results provided more detailed understanding of the effect of molecular structure on the self-assembled structures of amphiphilic dendrimers on solid surfaces, shedding light on the controlled microstructure and wettability of functional surface by modulating the length of hydrophobic chains of dendrimers and a potential application of dendrimer-substrate combinations.

Bio-inspired peptide decorated dendrimers for a robust antibacterial coating on hydroxyapatite

SSP-PAMAM-NH₂ inspired by the salivary statherin protein can tightly adsorb on the HA surface to achieve long-term antibacterial activity.