Dendrimer-entrapped gold nanoparticles modified with folic acid for targeted gene delivery applications

Insight Into Interfacial Behaviors between Doxorubicin and Zwitterion/PAMAM/CQD Hybrid Nanocarrier. A Molecular Dynamics Simulations Study

Poly(amidoamine) dendrimer (PAMAM)/carbon quantum dot (CQD) nanohybrids are promising candidates for many biomedical applications, including drug delivery. Effectively designing a hybrid nanocarrier requires a deep understanding of the interactions of the hybrid nanoparticle with the drug to ensure drug stability and therapeutic efficiency. In this study, we utilized fully atomistic molecular dynamics (MD) simulations to investigate the adsorption behavior of a doxorubicin (DOX) anticancer drug onto a zwitterion/PAMAM/CQD hybrid nanocarrier. The hybrid nanoparticles were composed of CQD, at two oxidation levels, grafted with PAMAM dendrimers of generation 3 (G3) or 4 (G4) decorated with zwitterion monomers. Our work reveals that the generation of the grafted dendrimer was the primary determinant of efficient adsorption of DOX, unlike the oxidation level of CQD or dendrimer surface chemistry. After grafting, the G4 dendrimers assume a more stretched conformation compared to the G3 dendrimers. This allowed DOX molecules to penetrate inside the dendritic cavities of G4 dendrimers, resulting in enhanced drug protection. The hydrophobic interaction, between the aromatic structure of DOX molecules and the nonpolar parts of dendrimers, has been proven to play a crucial role in mediating the adsorption of drug molecules. These findings provide valuable insights to assist in the design of a zwitterion/PAMAM/CQD hybrid nanoplatform for drug delivery applications.

Genetic Engineering of Dendritic Cells Using Partially Zwitterionic Dendrimer-Entrapped Gold Nanoparticles Boosts Efficient Tumor Immunotherapy

Effective processing and cross-priming of tumor neoantigen by dendritic cells (DCs) to T cells for spontaneous immune response generation to effectively kill cancer cells remain challenging in cancer immunotherapy. Here, we report a general approach to genetically engineer DCs through silencing their YTHDF1 protein (an important reader protein responsible for RNA m⁶A methylation) expression via a dendrimeric non-viral vector to boost effective tumor immunotherapy. Poly(amidoamine) dendrimers of generation 5 were partially decorated with mannose and 1,3-propanesultone and then entrapped with gold (Au) nanoparticles. The created dendrimer nanoplatform has an Au core size of 1.8 nm; possesses desired stability, good cytocompatibility, and excellent YTHDF1 siRNA compression ability; and enables targeted gene silencing of DCs overexpressing mannose receptors to upregulate the expression of CD80 and CD86, markers of DCs maturation, potentially leading to tumor antigen cross-presentation. With these properties owned, the combination of YTHDF1 silencing of DCs with programmed cell death-ligand 1 antibody can boost the best immunotherapy of a xenografted melanoma tumor model through the created antitumor immune responses. Findings in this study demonstrate a general approach of genetic engineering of DCs via a dendrimeric non-viral vector to effectively boost antitumor immunotherapy.

Effective CpG Delivery Using Zwitterion-Functionalized Dendrimer-Entrapped Gold Nanoparticles to Promote T Cell-Mediated Immunotherapy of Cancer Cells

Recently, cell-based immunotherapy has become one of the most promising ways to completely eliminate cancer. The major challenge is to effectively promote a proper immune response to kill the cancer cells by activated T cells. This study investigated the effect of T cell-mediated immunotherapy trigged by Au DENPs-MPC (zwitterion 2-methacryloyloxyethyl phosphorylcholine (MPC)-functionalized dendrimer-entrapped gold nanoparticles) loading oli-godeoxynucleotides (ODN) of unmethylated cytosine guanine dinucleotide (CPG). Here, we first synthesized Au DENPs-MPC, evaluated their capability to compress and transfect CpG-ODN to bone marrow dendritic cells (BMDCs), and investigated the potential to use T cells stimulated by matured BMDCs to inhibit the growth of tumor cells. The developed Au DENPs-MPC could apparently reduce the toxicity of Au DENPs, and enhanced transfer CpG-ODN to the BMDCs for the maturation as demonstrated by the 44.41-48.53% increase in different surface maturation markers. The transwell experiments certificated that ex vivo activated T cells display excellent anti-tumor ability, which could effectively inhibit the growth of tumor cells. These results suggest that Au DENPs-MPC can deliver CpG-ODN efficiently to enhance the antigen presentation ability of BMDCs to activate T cells, indicating that T cells-based immunotherapy mediated by Au DENPs-MPC loaded with CpG-ODN may become the most promising treatment of cancer.

Co-delivery of Dexamethasone and a MicroRNA-155 Inhibitor Using Dendrimer-Entrapped Gold Nanoparticles for Acute Lung Injury Therapy

Development of nanomedicines for effective therapy of acute lung injury (ALI), a common critical respiratory failure syndrome, remains to be challenging. We report here a unique design of a functional nanoplatform based on generation 5 (G5) poly(amidoamine) dendrimer-entrapped gold nanoparticles (Au DENPs) to co-deliver dexamethasone (Dex) and a microRNA-155 inhibitor (miR-155i) for combination chemotherapy and gene therapy of ALI. In this study, we synthesized Au DENPs with 10 Dex moieties attached per G5 dendrimer and an Au core diameter of 2.1 nm and used them to compress miR-155i. The generated polyplexes own a positive zeta potential (16-26 mV) and a small hydrodynamic diameter (175-230 nm) and display desired cytocompatibility and efficient miR-155i delivery to lipopolysaccharide (LPS)-activated alveolar macrophages, thus upregulating the suppressor of cytokine signaling 1 and IL-10 expression and downregulating the pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6). Likewise, as a synthetic glucocorticoid with a potent anti-inflammatory property, the attached Dex on the surface of Au DENPs could inhibit pro-inflammatory cytokine secretion by down-regulating cyclooxygenase-2 expression in the LPS-activated alveolar macrophages. The integration of Dex and miR-155i within one nanoformulation enables superior downregulation of pro-inflammatory cytokines for successful repair of damaged lung tissues in an ALI model, as demonstrated by histological examinations and pro-inflammatory cytokine downregulation in ALI lesion at the gene and protein levels. Such a combined chemotherapy and gene therapy strategy enabled by dendrimer nanotechnology may hold great promise to treat other types of inflammatory diseases.

Impact of molecular rigidity on the gene delivery efficiency of core-shell tecto dendrimers

We report the construction of two types of core-shell tecto dendrimers (CSTDs) with different core rigidities to illustrate the impact of molecular rigidity on their gene delivery efficiency. Our study reveals that CSTDs designed with rigid cores enable promoted gene delivery, providing many possibilities for a wide range of gene delivery-associated biomedical applications.

Dendrimer-Coated Gold Nanoparticles for Efficient Folate-Targeted mRNA Delivery In Vitro

Messenger RNA (mRNA) is not an attractive candidate for gene therapy due to its instability and has therefore received little attention. Recent studies show the advantage of mRNA over DNA, especially in cancer immunotherapy and vaccine development. This study aimed to formulate folic-acid-(FA)-modified, poly-amidoamine-generation-5 (PAMAM G5D)-grafted gold nanoparticles (AuNPs) and to evaluate their cytotoxicity and transgene expression using the luciferase reporter gene (FLuc-mRNA) in vitro. Nanocomplexes were spherical and of favorable size. Nanocomplexes at optimum nanoparticle:mRNA (w/w) binding ratios showed good protection of the bound mRNA against nucleases and were well tolerated in all cell lines. Transgene expression was significantly (p < 0.0001) higher with FA-targeted, dendrimer-grafted AuNPs (Au:G5D:FA) in FA receptors overexpressing MCF-7 and KB cells compared to the G5D and G5D:FA NPs, decreasing significantly (p < 0.01) in the presence of excess competing FA ligand, which confirmed nanocomplex uptake via receptor mediation. Overall, transgene expression of the Au:G5D and Au:G5D:FA nanocomplexes exceeded that of G5D and G5D:FA nanocomplexes, indicating the pivotal role played by the inclusion of the AuNP delivery system. The favorable properties imparted by the AuNPs potentiated an increased level of luciferase gene expression.

Recent Advances in Preclinical Research Using PAMAM Dendrimers for Cancer Gene Therapy

Carriers of genetic material are divided into vectors of viral and non-viral origin. Viral carriers are already successfully used in experimental gene therapies, but despite advantages such as their high transfection efficiency and the wide knowledge of their practical potential, the remaining disadvantages, namely, their low capacity and complex manufacturing process, based on biological systems, are major limitations prior to their broad implementation in the clinical setting. The application of non-viral carriers in gene therapy is one of the available approaches. Poly(amidoamine) (PAMAM) dendrimers are repetitively branched, three-dimensional molecules, made of amide and amine subunits, possessing unique physiochemical properties. Surface and internal modifications improve their physicochemical properties, enabling the increase in cellular specificity and transfection efficiency and a reduction in cytotoxicity toward healthy cells. During the last 10 years of research on PAMAM dendrimers, three modification strategies have commonly been used: (1) surface modification with functional groups; (2) hybrid vector formation; (3) creation of supramolecular self-assemblies. This review describes and summarizes recent studies exploring the development of PAMAM dendrimers in anticancer gene therapies, evaluating the advantages and disadvantages of the modification approaches and the nanomedicine regulatory issues preventing their translation into the clinical setting, and highlighting important areas for further development and possible steps that seem promising in terms of development of PAMAM as a carrier of genetic material.

Construction of Poly(amidoamine) Dendrimer/Carbon Dot Nanohybrids for Biomedical Applications

Design of intelligent hybrid nanoparticles that can integrate diagnosis and therapy components plays an important role in the field of nanomedicine. Poly(amidoamine) (PAMAM) dendrimers possessing a unique architecture and tunable functional groups have been widely developed for various biomedical applications. Carbon dots (CDs) are considered as a promising fluorescence probe or drug delivery system due to their stable fluorescence property and excellent biocompatibility. The distinctive merits of PAMAM dendrimers and CDs are amenable for them to be constructed as perfect nanohybrids for different biomedical applications, in particular for cancer nanomedicine. Here, the recent advances in the construction of PAMAM dendrimer/CD nanohybrids for diverse biomedical applications, in particular for sensing and cancer theranostics are summarized. Finally, the future perspectives of the PAMAM dendrimer/CD nanohybrids are also briefly discussed.

Induction of Cytokines by Nucleic Acid Nanoparticles (NANPs) Depends on the Type of Delivery Carrier

Recent insights into the immunostimulatory properties of nucleic acid nanoparticles (NANPs) have demonstrated that variations in the shape, size, and composition lead to distinct patterns in their immunostimulatory properties. While most of these studies have used a single lipid-based carrier to allow for NANPs' intracellular delivery, it is now apparent that the platform for delivery, which has historically been a hurdle for therapeutic nucleic acids, is an additional means to tailoring NANP immunorecognition. Here, the use of dendrimers for the delivery of NANPs is compared to the lipid-based platform and the differences in resulting cytokine induction are presented.

Targeted Combination of Antioxidative and Anti-Inflammatory Therapy of Rheumatoid Arthritis using Multifunctional Dendrimer-Entrapped Gold Nanoparticles as a Platform

Abundant reactive oxygen species and tumor necrosis factor-α (TNF-α) cytokine supply of M1-type macrophages boost rheumatoid arthritis (RA) pathological process. For efficient RA therapy, here a multifunctional nanoplatform is presented based on generation 5 (G5) poly(amidoamine) dendrimer-entrapped gold nanoparticles (Au DENPs) to achieve co-delivery of antioxidant alpha-tocopheryl succinate (α-TOS) and anti-inflammatory anti-TNF-α siRNA to macrophage cells. G5 dendrimers with amine termini are sequentially functionalized with 1,3-propane sultone (1,3-PS), α-TOS through a polyethylene glycol (PEG) spacer, and PEGylated folic acid (FA), and subsequently entrapped with Au NPs. The generated functional Au DENPs exhibit desired cytocompatibility, zwitterion-rendered antifouling property, and FA-mediated targeting specificity, enabling serum-enhanced siRNA delivery to M1-type macrophage cells. Meanwhile, the attached α-TOS affords enhanced oxidation resistance of macrophage cells. In vivo investigation shows that the treatment of a collagen-induced arthritis mouse model using α-TOS-modified Au DENPs/TNF-α siRNA polyplexes can achieve excellent combination therapy effect in inflammatory cytokines downregulation of RA lesion and bone erosions. The therapeutic efficacy is also supported by 3D micro-computed tomography analysis and TNF-α cytokine reduction of RA lesion joints in the mRNA, protein, and histology levels. The created multifunctional nanoplatform may be employed in antioxidative and anti-inflammatory combination therapy of RA.

Cationic cross-linked polymers containing labile disulfide and boronic ester linkages for effective triple responsive DNA release

Disruption of DNA carriers triggered by intracellular bio-stimulants has been broadly considered as most convenient strategy for efficient DNA delivery. In this direction, we have designed and synthesized pH, redox and ATP responsive cationic cross-linked polymers (CLPs) having disulfide and reversible boronic ester linkages. These CLPs also contain folate groups that are known for their targeting capability towards cancer cells. Biophysical studies showed that these cationic CLPs exhibited more effective DNA condensation in comparison to cationic linear polymers resulting in the formation of nano-sized polyplexes with sufficient positive zeta potentials and good colloidal stability at neutral pH (∼7.4). More interestingly, the polyplexes prepared from these CLPs have the ability to selectively release complexed DNA under conditions similar to those prevalent in cancer cells such as acidic pH, ATP rich surroundings or presence of glutathione, as revealed by ethidium bromide exclusion assay, agarose gel electrophoresis, AFM measurements, etc. Therefore, these cross-linked polymers have high potential of being effective non-viral gene delivery vehicles.

Adoptive cellular immunotherapy of tumors via effective CpG delivery to dendritic cells using dendrimer-entrapped gold nanoparticles as a gene vector

PEGylated Au DENPs ({(Au⁰)₂₅-G5·NH₂-mPEG₂₀}) are synthesized and used as a novel nonviral vector to deliver CpG to mature BMDCs for the subsequent activation of T cells for adoptive tumor immunotherapy.

RGD peptide-decorated micelles assembled from polymer-paclitaxel conjugates towards gastric cancer therapy

Development of polymer-drug conjugate capable of controlled drug release is urgently needed for gastric cancer therapy. Herein, arginine-glycine-aspartic acid (RGD)-decorated polyethylene glycol (PEG)-paclitaxel (PTX) conjugates containing disulfide linkage were synthesized. The amphiphilic PEG-PTX conjugates were found to assemble into micelles (RGD@Micelles), which would be decomposed under the reduction of glutathione (GSH) and finally release PTX in weakly acidic conditions characteristic of intracellular environment. The RGD@Micelles were spherical nanoparticles with an average hydrodynamic size of ˜50 nm, which were stable in physiological environment. The release of PTX from the micelles in response to GSH was investigated. In vitro cell assay suggested that the RGD@Micelles could target the gastric cancer cells and inhibit cell proliferation by inducing apoptosis. In vivo experiments indicated that the RGD@Micelles could be delivered to the tumor site and inhibit the tumor growth efficiently by releasing PTX inside the tumor cells. This type of micelles exhibited high therapeutic efficacy and low side effects, providing new insights into targeted drug delivery for gastric cancer therapy.

Exploiting the biomimetic and luminescence properties of multivalent dendrimer-semiconductor nanohybrid materials in the ultra-low level determination of folic acid

In view of the enhanced generation of folate receptors in cancerous cells and diseases linked to the deficiency of folic acid, such as anemia, mental devolution, congenital malformation, etc., the development of a simple method for the ultra-sensitive determination of folic acid remains a long-standing issue for practical applications in medicine and biotechnology. Thus, the proposed luminescence based strategy involving multifunctional poly(amidoamine) (PAMAM) dendrimer encapsulated quantum dots (QDs) as a probe provides a simple, fast and efficient method for the selective determination of folic acid at the nano-molar level. Absorption and Fourier transform infra-red (FTIR) spectroscopy provide evidence of the binding of folic acid with dendrimer amine groups. The emission quenching of dendrimer encapsulated CdS QDs follows a linear Stern-Volmer plot with an exceedingly high value of the Stern-Volmer constant (K_SV = 8.4 × 10⁶ M^-1) facilitating a higher detection efficiency. Similar quenching analysis with dendrimer-ZnS QDs showed a slightly lower Stern-Volmer constant (K_SV = 2.29 × 10⁶ M^-1). The lower probing efficiency of the protein or amino acid capping of QDs has been explained through zeta potential measurements. The solvent polarity dependence suggests a charge transfer process responsible for the emission quenching of CdS QDs, which is static in nature as revealed by lifetime measurements. The determination of folic acid at this low level is not affected by possible interfering molecules, such as vitamin C, vitamin B₁₂ and uric acid. Calorimetric measurements showed that the exothermic binding of folic acid with a dendrimer follows enthalpy-entropy compensation. The detailed mechanistic aspect of interactions of folic acid with the QD probe helps in a better understanding of the detection process, which in turn can assist in developing a dendrimer based material for image analysis and drug delivery in folate receptor rich cells.

Dendrimer based theranostic nanostructures for combined chemo- and photothermal therapy of liver cancer cells in vitro

Here we report the synthesis of multifunctional nanocarriers based on PAMAM dendrimers generation (G) 4.0, 5.0 and 6.0 fixed to polydopamine (PDA) coated magnetite nanoparticles (Fe₃O₄). Synthesized nanoplatforms were characterized by transmission electron microscopy (TEM), the electrokinetic (zeta) potential, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and magnetic resonance imaging (MRI). Further, we show as a proof of concept that nanocarriers functionalized with G 5.0 could be successfully applied in combined chemo- and photothermal therapy (CT-PTT) of the liver cancer cells. The cooperative effect of the modalities mentioned above led to higher mortality of cancer cells when compared to their individual performance. Moreover, the performed in vitro studies revealed that the application of dual therapy triggered the desired cell death mechanism-apoptosis. Furthermore, performed tests using Magnetic Resonance Imaging (MRI) showed that our materials have competitive contrast properties. Overall, the functionality of dendrimers has been extended by merging them with magnetic nanoparticles resulting in multifunctional hybrid nanostructures that are promising smart drug delivery system for cancer therapy.

PAMAM dendrimers as efficient drug and gene delivery nanosystems for cancer therapy

Drug delivery systems for cancer chemotherapy are employed to improve the effectiveness and decrease the side-effects of highly toxic drugs. Most chemotherapy agents have indiscriminate cytotoxicity that affects normal, as well as cancer cells. To overcome these problems, new more efficient nanosystems for drug delivery are increasingly being investigated. Polyamidoamine (PAMAM) dendrimers are an example of a versatile and reproducible type of nanocarrier that can be loaded with drugs, and modified by attaching target-specific ligands that recognize receptors that are over-expressed on cancer cells. PAMAM dendrimers with a high density of cationic charges display electrostatic interactions with nucleic acids (DNA, siRNA, miRNA, etc.), creating dendriplexes that can preserve the nucleic acids from degradation. Dendrimers are prepared by conducting several successive "generations" of synthetic reactions so their size can be easily controlled and they have good uniformity. Dendrimers are particularly well-suited to co-delivery applications (simultaneous delivery of drugs and/or genes). In the current review, we discuss dendrimer-based targeted delivery of drugs/genes and co-delivery systems mainly for cancer therapy.

Enhanced Delivery of Therapeutic siRNA into Glioblastoma Cells Using Dendrimer-Entrapped Gold Nanoparticles Conjugated with β-Cyclodextrin

We describe a safe and highly effective non-viral vector system based on β-cyclodextrin (β-CD)-modified dendrimer-entrapped gold nanoparticles (Au DENPs) for improved delivery small interfering RNA (siRNA) to glioblastoma cells. In our approach, we utilized amine-terminated generation 5 poly(amidoamine) dendrimers partially grafted with β-CD as a nanoreactor to entrap Au NPs. The acquired β-CD-modified Au DENPs (Au DENPs-β-CD) were complexed with two different types of therapeutic siRNA (B-cell lymphoma/leukemia-2 (Bcl-2) siRNA and vascular endothelial growth factor (VEGF) siRNA). The siRNA compression ability of the Au DENPs-β-CD was evaluated by various methods. The cytocompatibility of the vector/siRNA polyplexes was assessed by viability assay of cells. The siRNA transfection capability of the formed Au DENPs-β-CD vector was evaluated by flow cytometric assay of the cellular uptake of the polyplexes and Western blot assays of the Bcl-2 and VEGF protein expression. Our data reveals that the formed Au DENPs-β-CD carrier enables efficiently delivery of siRNA to glioma cells, has good cytocompatibility once complexed with the siRNA, and enables enhanced gene silencing to inhibit the expression of Bcl-2 and VEGF proteins. The developed Au DENPs-β-CD vector may be used for efficient siRNA delivery to different biosystems for therapeutic purposes.

PEGylated dendrimer-entrapped gold nanoparticles with low immunogenicity for targeted gene delivery

The designed Au DENPs-PEG-FA compacts pDNA into cells to enhance gene transfection efficiency.

Multifunctional PEI-entrapped gold nanoparticles enable efficient delivery of therapeutic siRNA into glioblastoma cells

Multifunctional PEI-entrapped gold nanoparticles modified with RGD peptide via a PEG spacer enable efficient therapeutic siRNA delivery to glioblastoma cells.

Efficient delivery of therapeutic siRNA into glioblastoma cells using multifunctional dendrimer-entrapped gold nanoparticles

AIM

To synthesize the arginine-glycine-aspartic (RGD) functionalized dendrimer-entrapped gold nanoparticles (Au DENPs) for siRNA delivery to induce gene silencing of cancer cells in vitro and in vivo.

MATERIALS & METHODS

Au DENPs modified with RGD peptide via a polyethylene glycol spacer were used as a vector of two distinct small interfering RNAs (siRNAs) (VEGFvascular endothelial growth factor siRNA and B-cell lymphoma/leukemia-2 siRNA), and the physicochemical properties, cytocompatibility and transfection efficiency of Au DENP/siRNA polyplexes were characterized.

RESULTS

The Au DENP/siRNA polyplexes with good cytocompatibility and highly efficient transfection capacity can be used for the transfection of siRNAs.

CONCLUSION

The developed functional RGD-modified Au DENPs may be used for efficient gene therapy of different types of cancer.

A non-viral suicide gene delivery system traversing the blood brain barrier for non-invasive glioma targeting treatment

Herpes simplex virus type I thymidine kinase gene (HSV-TK) in viral vector is a promising strategy against glioblastoma multiforme (GBM). However, the biosafety risk restricts its application in clinic. In this work, poly (l-lysine)-grafted polyethylenimine (PEI-PLL), which combines the high transfection efficiency of polyethylenimine and the good biodegradability of poly (l-lysine), was adopted as the non-viral vector backbone. Angiopep-2, a blood brain barrier (BBB) crossing and glioma targeting bifunctional peptide was conjugated on PEI-PLL via polyethyleneglycol (PEG) and designated as PPA. The optimal transfection ratio of PPA/DNA complexes nanoparticles (PPA NPs) was firstly characterized. Next, the glioma targeting of the PPA NPs was confirmed through cellular uptake and transfection analysis. The in vivo imaging studies demonstrated that the PPA NPs could not only penetrate BBB but also accumulate in striatum and cortex via systemic administration. Moreover, the PPA/HSV-TK NPs showed remarkably anti-glioma effect and survival benefit in an invasive orthotopic human GBM mouse model through inhibiting proliferation and inducing apoptosis (p<0.05 vs control). This study firstly illustrated that the cationic polymer PPA could be exploited as an efficient gene vector to cross the BBB, and innovatively provided a potential non-viral nanomedicine for noninvasive suicide gene therapy in the glioma treatment.

One-step Conjugation of Glycyrrhetinic Acid to Cationic Polymers for High-performance Gene Delivery to Cultured Liver Cell

Gene therapies represent a promising therapeutic route for liver cancers, but major challenges remain in the design of safe and efficient gene-targeting delivery systems. For example, cationic polymers show good transfection efficiency as gene carriers, but are hindered by cytotoxicity and non-specific targeting. Here we report a versatile method of one-step conjugation of glycyrrhetinic acid (GA) to reduce cytotoxicity and improve the cultured liver cell -targeting capability of cationic polymers. We have explored a series of cationic polymer derivatives by coupling different ratios of GA to polypropylenimine (PPI) dendrimer. These new gene carriers (GA-PPI dendrimer) were systematically characterized by UV-vis,(1)H NMR titration, electron microscopy, zeta potential, dynamic light-scattering, gel electrophoresis, confocal microscopy and flow cytometry. We demonstrate that GA-PPI dendrimers can efficiently load and protect pDNA, via formation of nanostructured GA-PPI/pDNA polyplexes. With optimal GA substitution degree (6.31%), GA-PPI dendrimers deliver higher liver cell transfection efficiency (43.5% vs 22.3%) and lower cytotoxicity (94.3% vs 62.5%, cell viability) than the commercial bench-mark DNA carrier bPEI (25 kDa) with cultured liver model cells (HepG2). There results suggest that our new GA-PPI dendrimer are a promising candidate gene carrier for targeted liver cancer therapy.

Dendrimer-entrapped gold nanoparticles modified with β-cyclodextrin for enhanced gene delivery applications

Dendrimer-entrapped gold nanoparticles modified with β-cyclodextrin can be synthesized and used as a non-viral vector for enhanced gene delivery applications.

Utilising inorganic nanocarriers for gene delivery

The delivery of genetic materials into cells to elicit cellular response has been extensively studied by biomaterials scientists globally.

Partially PEGylated dendrimer-entrapped gold nanoparticles: a promising nanoplatform for highly efficient DNA and siRNA delivery

Partially PEGylated dendrimer-entrapped gold nanoparticles can be used as a promising nanoplatform for highly efficient pDNA and siRNA delivery.

Modular Integration of Upconverting Nanocrystal-Dendrimer Composites for Folate Receptor-Specific NIR Imaging and Light-Triggered Drug Release

Upconversion nanocrystals (UCNs) display near-infrared (NIR)-responsive photoluminescent properties for NIR imaging and drug delivery. The development of effective strategies for UCN integration with other complementary nanostructures for targeting and drug conjugation is highly desirable. This study reports on a core/shell-based theranostic system designed by UCN integration with a folate (FA)-conjugated dendrimer for tumor targeting and with photocaged doxorubicin as a cytotoxic agent. Two types of UCNs (NaYF4:Yb/Er (or Yb/Tm); diameter = ≈50 to 54 nm) are described, each displaying distinct emission properties upon NIR (980 nm) excitation. The UCNs are surface modified through covalent attachment of photocaged doxorubicin (ONB-Dox) and a multivalent FA-conjugated polyamidoamine (PAMAM) dendrimer G5(FA)6 to prepare UCN@(ONB-Dox)(G5FA). Surface plasmon resonance experiments performed with G5(FA)6 dendrimer alone show nanomolar binding avidity (KD = 5.9 × 10(-9) M) to the folate binding protein. This dendrimer binding corresponds with selective binding and uptake of UCN@(ONB-Dox)(G5FA) by FAR-positive KB carcinoma cells in vitro. Furthermore, UCN@(ONB-Dox)(G5FA) treatment of FAR(+) KB cells inhibits cell growth in a light dependent manner. These results validate the utility of modularly integrated UCN-dendrimer nanocomposites for cell type specific NIR imaging and light-controlled drug release, thus serving as a new theranostic system.

Designing Dendrimer and Miktoarm Polymer Based Multi-Tasking Nanocarriers for Efficient Medical Therapy

To address current complex health problems, there has been an increasing demand for smart nanocarriers that could perform multiple complimentary biological tasks with high efficacy. This has provoked the design of tailor made nanocarriers, and the scientific community has made tremendous effort in meeting daunting challenges associated with synthetically articulating multiple functions into a single scaffold. Branched and hyper-branched macromolecular architectures have offered opportunities in enabling carriers with capabilities including location, delivery, imaging etc. Development of simple and versatile synthetic methodologies for these nanomaterials has been the key in diversifying macromolecule based medical therapy and treatment. This review highlights the advancement from conventional "only one function" to multifunctional nanomedicine. It is achieved by synthetic elaboration of multivalent platforms in miktoarm polymers and dendrimers by physical encapsulation, covalent linking and combinations thereof.

Self-Assembled Hybrids of Fluorescent Carbon Dots and PAMAM Dendrimers for Epirubicin Delivery and Intracellular Imaging

Advanced nanomaterials integrating imaging and therapeutic modalities on a single platform offers a new horizon in current cancer treatment strategies. Recently, carbon dots (CQDs) have been successfully employed for bioimaging of cancer cells. In the present study, luminescent CQDs with anionic terminus and cationic acetylated G5 poly(amido amine) (G5-Ac85) dendrimers were combined via noncovalent interactions to form self-assembled fluorescent hybrids. The fluorescence of CQDs in hybrids is enhanced in the vicinity of primary amine groups of dendrimers, making them suitable as cellular imaging probes. Encapsulation of chemo-drug epirubicin (EPI) in the dendrimer interiors endowed the fluorescent hybrids with therapeutic potential. The in vitro release of an entrapped EPI drug from CQDs@EPI⊂G5-Ac85 hybrids was faster in an acidic environment than under physiological conditions. Herein, multifunctional CQDs@EPI⊂G5-Ac85 hybrids serve as a dual-emission delivery system, to track the intracellular distribution and cytotoxic effects of EPI drugs. Green emission properties of CQDs were used for fluorescence microscopic imaging and cellular uptake by flow cytometry. Cell cycle analysis, field-emission scanning electron microscopy (FE-SEM), reactive oxygen species (ROS) generation, and up-regulation of apoptotic signaling genes unanimously demonstrated the apoptosis inducing ability of CQDs@EPI⊂G5-Ac85 hybrids in breast cancer (MCF-7) cells. Therefore, we have evaluated CQDs@EPI⊂G5-Ac85 hybrids as prospective candidates to achieve simultaneous imaging and drug delivery in cancer cells.

RGD peptide-modified dendrimer-entrapped gold nanoparticles enable highly efficient and specific gene delivery to stem cells

We report the use of arginine-glycine-aspartic (Arg-Gly-Asp, RGD) peptide-modified dendrimer-entrapped gold nanoparticles (Au DENPs) for highly efficient and specific gene delivery to stem cells. In this study, generation 5 poly(amidoamine) dendrimers modified with RGD via a poly(ethylene glycol) (PEG) spacer and with PEG monomethyl ether were used as templates to entrap gold nanoparticles (AuNPs). The native and the RGD-modified PEGylated dendrimers and the respective well characterized Au DENPs were used as vectors to transfect human mesenchymal stem cells (hMSCs) with plasmid DNA (pDNA) carrying both the enhanced green fluorescent protein and the luciferase (pEGFPLuc) reporter genes, as well as pDNA encoding the human bone morphogenetic protein-2 (hBMP-2) gene. We show that all vectors are capable of transfecting the hMSCs with both pDNAs. Gene transfection using pEGFPLuc was demonstrated by quantitative Luc activity assay and qualitative evaluation by fluorescence microscopy. For the transfection with hBMP-2, the gene delivery efficiency was evaluated by monitoring the hBMP-2 concentration and the level of osteogenic differentiation of the hMSCs via alkaline phosphatase activity, osteocalcin secretion, calcium deposition, and von Kossa staining assays. Our results reveal that the stem cell gene delivery efficiency is largely dependent on the composition and the surface functionality of the dendrimer-based vectors. The coexistence of RGD and AuNPs rendered the designed dendrimeric vector with specific stem cell binding ability likely via binding of integrin receptor on the cell surface and improved three-dimensional conformation of dendrimers, which is beneficial for highly efficient and specific stem cell gene delivery applications.

Dendrimer–nanoparticle conjugates in nanomedicine

Nanomedicine can take advantage of the recent developments in nanobiotechnology research areas for the creation of platforms with superior drug carrier capabilities, selective responsiveness to the environment, unique contrast enhancement profiles and improved accumulation at the disease site. Colloidal inorganic nanoparticles (NPs) have been attracting considerable interest in biomedicine, from drug and gene delivery to imaging, sensing and diagnostics. It is essential to modify the NPs surface to have enhanced biocompatibility and reach multifunctional systems for the in vitro and in vivo applications, especially in delivering drugs locally and recognizing overexpressed biomolecules. This paper describes the rational design for dendrimer–nanoparticle conjugates elaboration and reviews their state-of-the-art uses as efficient nanomedicine tools.

RGD peptide-modified multifunctional dendrimer platform for drug encapsulation and targeted inhibition of cancer cells

Development of multifunctional nanoscale drug-delivery systems for targeted cancer therapy still remains a great challenge. Here, we report the synthesis of cyclic arginine-glycine-aspartic acid (RGD) peptide-conjugated generation 5 (G5) poly(amidoamine) dendrimers for anticancer drug encapsulation and targeted therapy of cancer cells overexpressing αvβ3 integrins. In this study, amine-terminated G5 dendrimers were used as a platform to be sequentially modified with fluorescein isothiocyanate (FI) via a thiourea linkage and RGD peptide via a polyethylene glycol (PEG) spacer, followed by acetylation of the remaining dendrimer terminal amines. The developed multifunctional dendrimer platform (G5.NHAc-FI-PEG-RGD) was then used to encapsulate an anticancer drug doxorubicin (DOX). We show that approximately six DOX molecules are able to be encapsulated within each dendrimer platform. The formed complexes are water-soluble, stable, and able to release DOX in a sustained manner. One- and two-dimensional NMR techniques were applied to investigate the interaction between dendrimers and DOX, and the impact of the environmental pH on the release rate of DOX from the dendrimer/DOX complexes was also explored. Furthermore, cell biological studies demonstrate that the encapsulation of DOX within the G5.NHAc-FI-PEG-RGD dendrimers does not compromise the anticancer activity of DOX and that the therapeutic efficacy of the dendrimer/DOX complexes is solely related to the encapsulated DOX drug. Importantly, thanks to the role played by RGD-mediated targeting, the developed dendrimer/drug complexes are able to specifically target αvβ3 integrin-overexpressing cancer cells and display specific therapeutic efficacy to the target cells. The developed RGD peptide-targeted multifunctional dendrimers may thus be used as a versatile platform for targeted therapy of different types of αvβ3 integrin-overexpressing cancer cells.

Effect of peptide content on the regulation of transgene expression by protein kinase Cα-responsive linear polyethylenimine-peptide conjugates

We examined a series of linear polyethylenimine (LPEI)-based nanocarriers that activate transgene expression in response to cancer-specific protein kinase Cα (PKCα). Eight types of LPEI-peptide conjugate differing in peptide content and number were synthesized using click chemistry. The conjugates could form polyplexes with pDNA through electrostatic interaction, but the degree of pDNA condensation, sizes, and surface charges of the resulting polyplexes depended on the pendant-peptide content and number. None of the polyplexes showed significant cytotoxicity toward human hepatoma cells (HepG2). Furthermore, pendant peptide content and number markedly affected transgene activation in response to PKCα. To achieve an all-or-none response to PKCα, we determined the optimum peptide content and number in LPEI-peptide conjugates as ≈6 mol% and ≈40 peptides/conjugate.

Applications of biosensing atomic force microscopy in monitoring drug and nanoparticle delivery

INTRODUCTION

The therapeutic effects of medicinal drugs not only depend on their properties, but also on effective transport to the target receptor. Here we highlight recent developments in this discipline and show applications of atomic force microscopy (AFM) that enable us to track the effects of drugs and the effectiveness of nanoparticle delivery at the single molecule level.

AREAS COVERED

Physiological AFM imaging enables visualization of topographical changes to cells as a result of drug exposure and allows observation of cellular responses that yield morphological changes. When we upgrade the regular measuring tip to a molecular biosensor, it enables investigation of functional changes at the molecular level via single molecule force spectroscopy.

EXPERT OPINION

Biosensing AFM techniques have generated powerful tools to monitor drug delivery in (living) cells. While technical developments in actual AFM methods have simplified measurements at relevant physiological conditions, understanding both the biological and technical background is still a crucial factor. However, due to its potential impact, we expect the number of application-based biosensing AFM techniques to further increase in the near future.

Oligoamine-tethered low generation polyamidoamine dendrimers as potential nucleic acid carriers

Oligoamine-tethered low generation PAMAM dendrimers (mG2–mG4) have been synthesized, which showed significantly higher transfection efficiency with minimal cytotoxicity in vitro.

Folic acid-modified laponite nanodisks for targeted anticancer drug delivery

Folic acid-modified laponite nanodisks can be used as an efficient platform for targeted delivery of doxorubicin via a receptor-mediated pathway.

Dendrimer-functionalized electrospun cellulose acetate nanofibers for targeted cancer cell capture applications

Multifunctional folic acid-functionalized dendrimers can be modified on the surface of electrospun cellulose acetate nanofibers for the specific capture of FAR-overexpressing cancer cells.