Grafting of poly(acrylic acid) onto poly(amidoamine)-functionalized graphene oxide via surface-mediated reversible addition-fragmentation chain transfer polymerization

A comparative study on solubility improvement of tetracycline and dexamethasone by poly(propylene imine) and polyamidoamine dendrimers: An insight into cytotoxicity and cell proliferation

Many of new chemical discovered in pharmaceutical industry are hydrophobic compounds. Various techniques have been used to overcome solubility problems of hydrophobic drugs in aqueous media. In the meantime, dendrimers have been considered for sustainability, nanoscale size, high carry capacity, tunable terminal functional groups in terms of drug delivery and solubility. In this work, we have synthesized poly(propylene imine) (PPI) dendrimer up to fifth generation using reduction of nitrile groups after Michael addition and also, polyamidoamine (PAMAM) dendrimer up to fourth generation using Michael addition and amidation reactions. fourth and fifth generations of PPI dendrimer and fourth and third generations of PAMAM dendrimer in different concentrations were used to evaluate the solubility of two hydrophobic drugs (tetracycline and dexamethasone). Furthermore, cytotoxicity of dendrimers and dendrimers/drugs hybrids was studied. The results showed that with increasing concentrations and also the generation of dendrimers, the solubility of these two hydrophobic drugs was increased. Cytotoxicity study through MTT assay against Osteoblast-like cell line (MG-63 cells) showed that dendrimers were relatively cytotoxic where adding dexamethasone caused higher cytotoxicity. However, tetracycline showed no significant effect on cytotoxicity whereas prevented cell proliferation.

Polymer grafting on graphene layers by controlled radical polymerization

In situ controlled radical polymerization (CRP) is considered as an important approach to graft polymer brushes with controlled grafting density, functionality, and thickness on graphene layers. Polymers are tethered with chain end or through its backbone to the surface or edge of graphene layers with two in situ polymerization methods of "grafting from" and "grafting through" and also a method based on coupling reactions known as "grafting to". The "grafting from" method relies on the propagation of polymer chains from the surface- or edge-attached initiators. The "grafting through" method is based on incorporation of double bond-modified graphene layers into polymer chains through the propagation reaction. The "grafting to" technique involves attachment of pre-fabricated polymer chains to the graphene substrate. Here, physical and chemical attachment approaches are also considered in polymer-modification of graphene layers. Combination of CRP mechanisms of reversible activation, degenerative (exchange) chain transfer, atom transfer, and reversible chain transfer with various kinds of grafting reactions makes it possible to selectively functionalize graphene layers. The main aim of this review is assessment of the recent advances in the field of preparation of polymer-grafted graphene substrates with well-defined polymers of controlled molecular weight, thickness, and polydispersity index. Study of the opportunities and challenges for the future works in controlling of grafting density, site-selectivity in grafting, and various topologies of the brushes with potential applications in stimuli-responsive surfaces, polymer composites, Pickering emulsions, coating technologies, and sensors is also considered.

Stimuli-responsive DOX release behavior of cross-linked poly(acrylic acid) nanoparticles

Cross-linked poly(acrylic acid) nanoparticles were synthesized via distillation precipitation polymerization of acrylic acid and ethylene glycol dimethacrylate withdifferent molar ratios. Spherical nanoparticles with diameters between 75 and 122 nm were synthesized and exhibited temperature and pH-responsive behaviors. However, this behavior was less pronounced for samples with higher cross-linking degrees. The potential of all nanoparticles as carriers for controlled release of doxorubicin (DOX) anti-cancer drug was examined at pH values of 1.2, 5.3 and 7.4. An obvious alleviation in burst release behavior and the amount of cumulative drug release was seen for all nanoparticles as the pH of the medium and the cross-linking degree of nanoparticle increased. Also kinetics of drug release was studied using mathematical models of zero-order, first-order, Higuchi, Korsmeyer-Peppas and Hixson-Crowell, where Higuchi and Korsmeyer-Peppas models best defined the kinetics of drug release.

Synthesis and characterization of poly(propylene imine)-dendrimer-grafted gold nanoparticles as nanocarriers of doxorubicin

The aim of current work is synthesis 4th-generation-poly(propylene imine) (PPI)-dendrimer modified gold nanoparticles (Au-G4A) as nanocarriers for doxorubicin (DOX) and studying in vitro drug release kinetics from nanocarriers into different media. Accordingly, AuNPs were synthesized by reduction of chloroauric acid (HAuCl₄) aqueous solution with trisodium citrate and modified with cysteamine to obtain amine-functionalized (Au-NH₂) nanoparticles. Au-NH₂ nanoparticles were used as multifunctional cores and participated in Michael addition of acrylonitrile and reduction process by lithium aluminum hydride (LAH) to synthesize Au-G4A nanoparticles. Also, peripheral primary amine groups of Au-G4A were conjugated with folic acid (FA) (Au-G4F) to study the bioconjugation effect on drug release behavior of nanostructures. Ultraviolet spectroscopy (UV-vis), atomic force microscopy (AFM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and thermal gravimetric analysis (TGA) were used to approve the synthesis of different nanostructures. Finally, Au-G4A and Au-G4F samples were loaded with DOX and exposed to environments with different pH values to examine the release properties of nanostructures. Also, drug release kinetics was investigated by fitting of experimental data with different release models. As a result, synthesized dendritic structures showed Higuchi and Korsmeyer-Peppas models release behavior due to better solubility of drug in release media with respect to dendrimer cavities and drug release through polymeric matrix respectively.

Photo, pH and redox multi-responsive nanogels for drug delivery and fluorescence cell imaging

A light, pH and redox triple-responsive spiropyran-based nanogel is prepared and applied for the efficient delivery of anticancer drugs and fluorescence cell imaging for the strong emission of merocyanine photoisomers.