Dendron Conjugates Research Articles

Janus Dendrimers as Nanocarriers of Ibuprofen, Chlorambucil and their Anticancer Activity.

Janus Dendrimer represents a novel class of synthetic nanocarriers. Since it is possible to introduce multiple drugs and target moieties, this helps the designing of new biocompatible forms with pharmacological activities comprised of different drugs with tailor-made functionalities, such as anticancer and nonsteroidal anti-inflammatory, which could improve the anticancer activity with less toxicity. This study aimed to determine the anticancer activity of the Janus dendrimers formed by two dendrons. One dendron conjugates with chlorambucil, and the other dendron conjugates with Ibuprofen. The cytotoxicity of the drug carriers was determined by the sulforhodamine B (SRB) assay for three cell lines. PC-3 (human prostatic adenocarcinoma), HCT-15 (human colorectal adenocarcinoma), MFC-7 (human breast cancer) and the COS-7 African green monkey kidney (used as a control) cell lines were seeded into 96-well plates at a density of 5x103 cells/well and cultured for 24 h before use. All the obtained compounds were characterized by 1H and 13C NMR one and two dimensions, UVvis, FTIR, MALDI-TOF, Electrospray mass, and FAB+. Microscopic images were taken in an Inverted microscope Nikon, Diaphot 300, 10x4 in culture medium. Janus dendrimers (G1 and G2) were synthesized via an azide-alkyne click-chemistry reaction attaching on one face dendrons with ibuprofen molecules and, on the other face, attached a chlorambucil- derivative. The IC50 behavior of the conjugates of the first and second generations showed anticancer activity against PC-3, HCT-15, and MFC-7 cell lines. The second generation was more active against PC-3, HCT-15 and MFC-7 with IC50 of 3.8±0.5, 3.0±0.2 and 3.7 ± 1.1 mM, respectively. The new Janus dendrimers with anticancer chlorambucil and nonsteroidal antiinflammatory Ibuprofen can improve the anticancer activity of chlorambucil with less toxicity. Now, we are working on the synthesis of new Janus dendrimers using the most effective and fine methods. Moreover, we hope that we shall be able to obtain different generations that are more selective against cancer cells.

Prednisone and ibuprofen conjugate Janus dendrimers and their anticancer activity

Drug release from hyperbranched Janus dendrimer-drug conjugates and their subsequent activity are influenced by the different drugs in each dendron and the linker. To understand these effects, we synthetized new Janus-type dendrimers of first and second generation. One dendron with 2,2-Bis(hydroxymethyl)propionic acid functionalized with ibuprofen and the second dendron was obtained with 3-aminopropanol-amidoamine and prednisone. The dendrimers were obtained by copper(I)-catalyzed Click azide-alkyne cycloaddition for the formation of a triazole as a dendrimeric nucleus of Janus dendrimer conjugates are reported.The influence of ibuprofen, prednisone, and spacer on cancer activity of Janus dendrimers conjugates is reported. The IC50 values of the anticancer activity on cancer cell lines the Janus dendrimer of second generation was higher in comparison to the first generation dendrimer. Similarly, the anticancer activity was higher compared to the dendron conjugates. Also, no cytotoxic effects of dendrons and dendrimers on non-cancerous kidney COS-7 cell line was observed. The interesting anticancer activity of the prepared prednisone-ibuprofen Janus dendrimer conjugates suggest that the dendrimers could be of potential use as new anticancer drug.

Antisense Peptide Nucleic Acid-Diaminobutanoic Acid Dendron Conjugates with SbmA-Independent Antimicrobial Activity against Gram-Negative Bacteria.

Precision antisense antibacterial agents may be developed into novel antibiotics in the fight against multidrug-resistant Gram-negative bacteria. In this study, a series of diaminobutanoic acid (DAB) dendrons are presented as novel carriers for the delivery of antisense antibacterial peptide nucleic acids (PNAs). The dendron–PNA conjugates targeting the essential acpP gene exhibit specific antisense antimicrobial bactericidal activity against Escherichia coli and Klebsiella pneumoniae at one-digit micromolar concentrations, while showing low toxicity to human cells. One compound selected from a structure–activity relationship series showed high stability in mouse and human serum (t1/2 ≫ 24 h) as well as in vivo activity against a multidrug-resistant, extended spectrum beta-lactamase-producing E. coli in a murine peritonitis model. The compound was also well tolerated in mice upon i.v. administration up to a dose of 20 mg/kg, and in vivo fluorescence imaging indicated clearance via renal excretion with slight accumulation in the kidneys and liver. Thus, DAB-based dendrons constitute a promising new chemistry platform for development of effective delivery agents for antibacterial drugs with possible in vivo use.

Structure and Function Analysis of DNA Monolayers Created from Self-Assembling DNA-Dendron Conjugates.

Short sequences of DNA immobilized on gold surfaces can be used to capture an array of target molecules because of their high level of specificity. Depending on the nature of the target molecules, the proper density and distribution of the immobilized DNA molecules are fundamental to the quality of the sensor. With the aim to control the packing density and minimize the heterogeneity of the surfaces, DNA-dendron conjugate molecules were synthesized in solution and used to make self-assembled monolayers of single-stranded DNA surfaces on gold. The headgroups used were polyamido amine dendrons (cleaved cystamine core dendrimers) of generations two through five. The structural composition of these self-assembled monolayers was characterized using grazing angle Fourier-transform infrared and X-ray photoelectron spectroscopies. Surface plasmon resonance was used to measure surface densities of the probe monolayers and each monolayer's ability to capture fully complementary DNA strands from solution. The surface density of the probe monolayers was found to decrease with increasing dendron generation number, while the hybridization efficiency increased with increasing dendron generation number.

Design, Synthesis, and Self-Assembly Studies of a Suite of Monodisperse, Facially Amphiphilic, Protein-Dendron Conjugates.

The custom design of protein-dendron amphiphilic macromolecules is at the forefront of macromolecular engineering. Macromolecules with this architecture are very interesting because of their ability to self-assemble into various biomimetic nanoscopic structures. However, to date, there are no reports on this concept due to technical challenges associated with the chemical synthesis. Towards that end, herein, a new chemical methodology for the modular synthesis of a suite of monodisperse, facially amphiphilic, protein-dendron bioconjugates is reported. Benzyl ether dendrons of different generations (G1-G4) are coupled to monodisperse cetyl ethylene glycol to form macromolecular amphiphilic activity-based probes (AABPs) with a single protein reactive functionality. Micelle-assisted protein labeling technology is utilized for site-specific conjugation of macromolecular AABPs to globular proteins to make monodisperse, facially amphiphilic, protein-dendron bioconjugates. These biohybrid conjugates have the ability to self-assemble into supramolecular protein nanoassemblies. Self-assembly is primarily mediated by strong hydrophobic interactions of the benzyl ether dendron domain. The size, surface charge, and oligomeric state of protein nanoassemblies could be systematically tuned by choosing an appropriate dendron or protein of interest. This chemical method discloses a new way to custom-make monodisperse, facially amphiphilic, protein-dendron bioconjugates.

Photoresponsive self-assembled hexameric capsules based on calix[4]resorcinarenes bearing azobenzene dendron conjugates as side chains.

We synthesized calix[4]resorcinarenes bearing various azobenzene dendron conjugates as side chains, wherein the azobenzene moiety is a photoresponsive unit and the dendron moiety is a capsule-destabilizing unit, and then studied the photoresponsive properties of their self-assembled hexameric capsules in conjunction with guest encapsulation in H2O-saturated CDCl3. It was found that correlation between the trans-to-cis photoisomerization of the azobenzene dendron side chains of hosts and the consequent capsule destabilization leading to guest release largely depends on the nature of the dendron moieties, such as their steric bulkiness or hydrophilicity.

Effects of molecular geometry on the self-assembly of giant polymer–dendron conjugates in condensed state

A series of giant polymer-dendron conjugates with a dendron head and a linear polymer tail were synthesized via"click" chemistry between azide-functionalized polystyrene (PS(N), N: degree-of-polymerization) and t-butyl protected, alkyne-functionalized second generation dendron (tD), followed by a deprotection process to generate a dendron termini possessing nine carboxylic acid groups. The molecular structures were confirmed by nuclear magnetic resonance, size-exclusion chromatographic analyses, and matrix-assisted laser desorption ionization time-of-flight mass spectra. These well-defined conjugates can serve as a model system to study the effects of the molecular geometries on the self-assembly behaviour, as compared with their linear analogues. Four phase morphologies found in flexible linear diblock copolymer systems, including lamellae, bicontinuous double gyroids, hexagonal packed cylinders, and body-centred cubic packed spheres, were observed in this series of conjugates based on the results of small angle X-ray scattering and transmission electron microscopy. All of the domain sizes in these phase separated structures were around or less than 10 nm. A 'half' phase diagram was constructed based on the experimental results. The geometrical effect was found not only to enhance the immiscibility between the PS(N) tail and dendron head, but also systematically shift all of the phase boundaries towards higher volume fractions of the PS(N) tails, resulting in an asymmetrical phase diagram. This study may provide a pathway to the construction of ordered patterns of sub-10 nm feature size using polymer-dendron conjugates.

Quantitative analysis of dendron-conjugated cisplatin-complexed gold nanoparticles using scanning particle mobility mass spectrometry

We report a high-resolution and traceable method to quantify the drug loading on nanoparticle-based cancer therapeutics, and demonstrate this method using a model cisplatin functionalized dendron-gold nanoparticle (AuNP) conjugate. Electrospray differential mobility analysis (ES-DMA) provides upstream size classification based on the electrical mobility of AuNP conjugates in aerosol form following electrospray conversion from the aqueous suspension. A condensation particle counter (CPC) and inductively coupled plasma mass spectrometer (ICP-MS) provide the principal downstream quantification. CPC and ICP-MS yield complementary number-based and elemental mass-based particle size distributions, respectively. Conjugation using three different dendron formulations was differentiated based on changes in the mean mobility particle size. The subsequent cisplatin complexation to the dendron conjugates was quantified by coupling ES-DMA with ICP-MS. Discrete AuNP clusters (e.g., dimers, trimers) could be resolved from the relative quantity of atoms (i.e., Au and Pt) per particle after separation by ES-DMA. Surface density of cisplatin on Au was shown to be proportional to the density of carboxylic groups present and was independent of the state of AuNP clustering. Additionally, we found that colloidal stability of the conjugate is inversely proportional to the surface loading of cisplatin. This study demonstrates a prototype methodology to provide traceable quantification and to determine other important formulation factors relevant to therapeutic performance.

Tuning polymersome surfaces: functionalization with dendritic groups

The conjugation of dendrons having varying peripheral functionalities to polymer vesicles, commonly referred to as polymersomes, provides an opportunity to significantly alter the polymersome surface chemistry in a single step while leaving intact the block copolymers responsible for assembly. In this work, polymersomes with surface azide groups were prepared from poly(1,2-butadiene)-poly(ethylene oxide) (PBD-PEO) and poly(e-caprolactone)-PEO (PCL-PEO) block copolymers and were functionalized with polyester dendrons having focal point alkyne moieties and peripheral hydroxyls, amines, or guanidines. The release rates of a small molecule rhodamine B and a rhodamine B-labeled protein from naked and functionalized polymersomes were investigated and the presence of dendritic groups was found to have a minimal effect. All of the naked and functionalized polymersomes were found to be nontoxic at all concentrations tested, except for the guanidine functionalized polymersomes which did impart some toxicity at the highest concentrations tested. The cell uptake of the different polymersomes was compared and it was found that the guanidine functionalized polymersomes exhibited increased cell uptake relative to all other materials. Further studies of this phenomenon suggested that the uptake is mediated by endocytosis and possibly direct translocation across the membrane.

Protein–dendron conjugates for DNA binding: understanding the effect of the protein core on multivalency

In this work we have used molecular dynamics simulations to explore the binding between two different protein–dendron conjugates and double stranded DNA. Different protein cores protect the binding site from the external environment, but can also influence the multivalent recognition between the spermine ligands of the dendron and the DNA.

Fabrication of “Clickable” Hydrogels via Dendron−Polymer Conjugates

Functionalizable hydrogels are of great interest as three-dimensional (3D) scaffolds for cell growth and tissue engineering. The ability to covalently immobilize biologically relevant molecules with accurate control of their density within the hydrogel matrix is highly desirable. Dendron−polymer conjugates prepared via Huisgen type “click” reaction provides a unique precursor for reactive hydrogels. A family of dendron−polymer conjugates were prepared by coupling second- and third-generation alkyne appended polyester dendrons with linear poly(ethylene glycol) diazides, PEG2K and PEG6K. Controlled cross-linking of alkyne-functionalized dendron−polymer−dendron conjugates with a hydrophilic diazide provides hydrogels with gelation efficiencies greater than 80%. Excess leftover alkynes can be used to functionalize these hydrogels as desired. Fine tuning of degree of cross-linking and functionalization is demonstrated by immobilization of streptavidin.

Precisely Defined Protein–Polymer Conjugates: Construction of Synthetic DNA Binding Domains on Proteins by Using Multivalent Dendrons

Nature has evolved proteins and enzymes to carry out a wide range of sophisticated tasks. Proteins modified with functional polymers possess many desirable physical and chemical properties and have applications in nanobiotechnology. Here we describe multivalent Newkome-type polyamine dendrons that function as synthetic DNA binding domains, which can be conjugated with proteins. These polyamine dendrons employ naturally occurring spermine surface groups to bind DNA with high affinity and are attached onto protein surfaces in a site-specific manner to yield well-defined one-to-one protein-polymer conjugates, where the number of dendrons and their attachment site on the protein surface are precisely known. This precise structure is achieved by using N-maleimido-core dendrons that selectively react via 1,4-conjugate addition with a single free thiol group on the protein surface--either Cys-34 of bovine serum albumin (BSA) or a genetically engineered cysteine mutant of Class II hydrophobin (HFBI). This reaction can be conducted in mild aqueous solutions (pH 7.2-7.4) and at ambient temperature, resulting in BSA- and HFBI-dendron conjugates. The protein-dendron conjugates constitute a specific biosynthetic diblock copolymer and bind DNA with high affinity, as shown by ethidium bromide displacement assay. Importantly, even the low-molecular-weight first-generation polyamine dendron (1 kDa) can bind a large BSA protein (66.4 kDa) to DNA with relatively good affinity. Preliminary gene transfection, cytotoxicity, and self-assembly studies establish the relevance of this methodology for in vitro applications, such as gene therapy and surface patterning. These results encourage further developments in protein-dendron block copolymer-like conjugates and will allow the advance of functional biomimetic nanoscale materials.

Coupled Conformational Equilibria in β-Sheet Peptide−Dendron Conjugates

A series of peptide−dendron conjugates, based on an intrinsically α-helical, alanine-rich sequence, were constructed to explore how the conformational equilibria of each structural element can be conformationally coupled. The interdendron spacing was varied from i, i + 4 (2) to i, i +11 (9) to probe how the nature of the dendron interaction impacted the conformational properties. These studies revealed an α-helix to β-sheet conformational transition that occurred in water for peptide−dendron conjugates 4 (i, i + 6) and 8 (i, i + 10). Chiral transfer from the peptide backbone to the dendron helicity emerges only in the β-sheet forms of 4 and 8, revealing a synergistic coupling of the conformations of both structural elements.

Multivalent Dendrons for High‐Affinity Adhesion of Proteins to DNA

Strength in numbers: Multivalent dendrons that have an N-maleimido group at the focal point can be used to construct monodisperse one-to-one protein–dendron conjugates. The second generation polyamine dendron with spermine surface groups clearly imparts its high-affinity DNA binding to a protein of choice.