Reducing the cytotoxity of poly(amidoamine) dendrimers by modification of a single layer of carboxybetaine

Potential anti-adhesion activity of novel carbosilane zwitterionic dendrimers against eukaryotic and prokaryotic pathogenic microorganisms

The development of biofilms on different surfaces continues to be a major public health problem. The antimicrobial resistance and the difficulty of finding drugs capable of combating these established biofilms generates the urgent need to find compounds that prevent cells from settling and establishing of these complex communities of microorganisms. Zwitterionic modification of nanomaterials allows the formation of a hydration layer, and this highly hydrophilic surface provides antifouling properties as well as a good biocompatibility by preventing non-specific interactions. Thus, they are appropriate candidates to prevent microbial adhesion to different surfaces and, in consequence, avoid biofilm formation. For this reason, we have incorporated zwitterionic moieties in multivalent systems, as are carbosilane dendrimers. Characterization of these systems was performed using nuclear magnetic resonance and mass spectrometry. It has been analysed if the new molecules have capacity to inhibit the biofilm formation in Candida albicans, Staphylococcus aureus and Pseudomonas aeruginosa. The results showed that they were more effective against S. aureus, observing a biofilm reduction of 81.5% treating with 32 mg/L of G2SiZWsf dendrimer and by 72.5% using 32 mg/L of the G3SiZWsf dendrimer. Finally, the absence of cytotoxicity was verified by haemolysis and cytotoxicity studies in human cells lines.

Spontaneously Restoring Specific Bioaffinity of RGD in Linear RGD-containing Peptides by Conjugation with Zwitterionic Dendrimers

Peptides are more versatile than small molecule drugs, but their specific bioaffinities are usually lower than their original native proteins because of the loss of preferred conformations. To overcome this key obstacle, we demonstrated a hydrogen bond-induced conformational constraint method to enhance the specific bioaffinities of peptides to achieve a high success rate by using linear RGD-containing peptides as a model of bioactive peptides. By performing molecular simulation, we found that the chemically immobilized linear CRGDS via cysteine (C) at the N-terminus on zwitterionic PAMAM G-5 can not only spontaneously restore the natural conformation of the RGD segment through the assistance of the dynamic hydrogen bond from serine (S) at the C-terminus of the peptide, but it can also narrow the distribution of all possible conformations. Consequently, the conjugates showed comparable or even better high affinity than native proteins without the use of conventional, labor-intensive, synthesis-based structure search methods to construct a binding conformation. In addition, the conjugates showed globular protein-like characteristics chemically, physically, and physiologically. They exhibited not only high efficacy and biosafety both in vitro and in vivo, but they also showed extremely high thermostability even upon boiling in a solution. This approach offers great design flexibility for reviving functional peptides without impairing their high specific affinity for their targets. STATEMENT OF SIGNIFICANCE: : In this work, we developed a swift approach to spontaneously restore the natural conformation of a linear peptide from a nature protein and thus enhance its specific bioaffinity instead of constructing a binding conformation by the labor-intensive, synthesis-based structure search method. In details, our new approach involves dynamically constraining the linear peptide on a zwitterionic PAMAM G-5 surface by a combination of chemical bonding at one terminus and dynamic hydrogen bonding at the other terminus of the linear peptide. The zwitterionic background offers abundant interaction sites for hydrogen bonding as well as resistance to nonspecific interactions. This approach fully restores the specific bioaffinity of RGD segments on a zwitterionic PAMAM G-5 through only one conjugation point at the C-terminus of the peptide. Moreover, the bioaffinity of all three types of RGD-containing peptides is successfully restored, which indicates the high rate of success of this approach in affinity restoring.

Development of an Ultrasmall and Biocompatible Platinum Nanozyme Encapsulated by Zwitterionic Dendrimer for Highly Sensitive Detection of Glucose

Many kinds of noble metal nanoparticles can mimic the peroxidase-like function of horseradish peroxidase, which results in their wide applications in bio-related detection and drug delivery. However, those metal nanoparticles usually have low stability and reduced catalytic activity in biological complex medium. Herein, a zwitterionic peroxidase-like enzyme has been developed, which has high stability in fibrinogen solutions and high sensitivity for glucose detection. Maleic anhydride, cysteamine, and zwitterionic peptide EKEKC (EK-5) were used to modify generation 5 poly(amido amine) dendrimers (G5 PAMAM) to prepare zwitterionic dendrimer G5MEKnC with nonfouling properties. Finally, the G5MEKnC-encapsulated platinum nanoparticles (Pt_n-G5MEK50C) were prepared by entrapping the platinum nanoparticles (1.40 nm) in the catalytic centers in the interior of G5MEK50C. Pt₅₅-G5MEK50C showed high stability in the buffer solution and the fibrinogen solution within 4 days. They also displayed high biocompatibility toward HeLa cells based on cytotoxicity results and morphological observations. Furthermore, the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine with H₂O₂ by Pt₅₅-G5MEK50C followed the Michaelis-Menten equation, which confirmed their peroxidase-like properties. The catalytic mechanism was due to the generation of ^•OH from H₂O₂. More importantly, the peroxidase-like ability of Pt₅₅-G5MEK50C was successfully used to establish a method for the determination of glucose concentration with a broad linear range of 1-2000 μM and a low detection limit of 0.1 μM. This method was highly accurate for the determination of glucose concentration in plasma. The zwitterionic dendrimer template enhanced the properties of Pt₅₅-G5MEK50C. Taken together, a new kind of biocompatible nanozyme has been developed and successfully used for the sensitive detection of glucose in bio-related medium.

Recent advances of zwitterionic based topological polymers for biomedical applications

Zwitterionic polymers, comprising hydrophilic anionic and cationic groups with the same total number of positive and negative charges on the same monomer residue, have received increasing attention due to their...

Relationship and improvement strategies between drug nanocarrier characteristics and hemocompatibility: What can we learn from the literature

This article discusses the various blood interactions that may occur with various types of nano drug-loading systems. Nanoparticles enter the blood circulation as foreign objects. On the one hand, they may cause a series of inflammatory reactions and immune reactions, resulting in the rapid elimination of immune cells and the reticuloendothelial system, affecting their durability in the blood circulation. On the other hand, the premise of the drug-carrying system to play a therapeutic role depends on whether they cause coagulation and platelet activation, the absence of hemolysis and the elimination of immune cells. For different forms of nano drug-carrying systems, we can find the characteristics, elements and coping strategies of adverse blood reactions that we can find in previous researches. These adverse reactions may include destruction of blood cells, abnormal coagulation system, abnormal effects of plasma proteins, abnormal blood cell behavior, adverse immune and inflammatory reactions, and excessive vascular stimulation. In order to provide help for future research and formulation work on the blood compatibility of nano drug carriers.

Computer Simulations on a pH-Responsive Anticancer Drug Delivery System Using Zwitterion-Grafted Polyamidoamine Dendrimer Unimolecular Micelles

Unimolecular micelles have attracted wide attention in the field of drug delivery because of their thermodynamic stability and uniform size distribution. However, their drug loading/release mechanisms at the molecular level have been poorly understood. In this work, the stability and drug loading/release behaviors of unimolecular micelles formed using generation-5 polyamidoamine-graft-poly(carboxybetaine methacrylate) (PAMAM(G5)-PCBMA) were studied by dissipative particle dynamics simulations. In addition, the unimolecular micelles formed using generation-5 polyamidoamine-graft-poly(ethyleneglycol methacrylate) (PAMAM(G5)-PEGMA) were used as a comparison. The simulation results showed that PAMAM(G5)-PCBMA can spontaneously form core-shell unimolecular micelles. The PAMAM(G5) dendrimer constitutes a hydrophobic core to load the doxorubicin (DOX), while the zwitterionic PCBMA serves as a protective shell to improve the stability of the unimolecular micelle. The DOX can be encapsulated into the cavity of PAMAM(G5) at the physiological pH 7.4. The drug loading efficiency and drug loading content showed some regularities with the increase in the drug concentration. At the acidic pH 5.0, the loaded DOX can be released gradually from the hydrophobic core. The comparison of DOX-loaded morphologies between the PAMAM(G5)-PCBMA system and PAMAM(G5)-PEGMA system showed that the former has better monodisperse stability. This work could offer theoretical guidance for the design and development of promising unimolecular micelles for drug delivery.

Novel zwitterionic vectors: Multi-functional delivery systems for therapeutic genes and drugs

Zwitterions consist of equal molar cationic and anionic moieties and thus exhibit overall electroneutrality. Zwitterionic materials include phosphorylcholine, sulfobetaine, carboxybetaine, zwitterionic amino acids/peptides, and other mix-charged zwitterions that could form dense and stable hydration shells through the strong ion-dipole interaction among water molecules and zwitterions. As a result of their remarkable hydration capability and low interfacial energy, zwitterionic materials have become ideal choices for designing therapeutic vectors to prevent undesired biosorption especially nonspecific biomacromolecules during circulation, which was termed antifouling capability. And along with their great biocompatibility, low cytotoxicity, negligible immunogenicity, systematic stability and long circulation time, zwitterionic materials have been widely utilized for the delivery of drugs and therapeutic genes. In this review, we first summarized the possible antifouling mechanism of zwitterions briefly, and separately introduced the features and advantages of each type of zwitterionic materials. Then we highlighted their applications in stimuli-responsive "intelligent" drug delivery systems as well as tumor-targeting carriers and stressed the multifunctional role they played in therapeutic gene delivery.

Zwitterionic Unimolecular Micelles with pH and Temperature Response: Enhanced In Vivo Circulation Stability and Tumor Therapeutic Efficiency

Circulation stability in vivo and stimuli-responsiveness under a tumor microenvironment of the polymeric prodrug micellar drug delivery systems are very critical to improve the tumor therapeutic efficiency. In this study, a series of polyamidoamine (PAMAM)-graft-poly(2-(diethylamino) ethyl methacrylate) (PDEAEMA)-block-poly(betaine sulfonate) (PSBMA) (PDS) unimolecular micelles were prepared via atom transfer radical polymerization. PAMAM served as a hydrophobic core to load the drug, the PDMAEMA segment was a middle layer to provide both thermo- and pH-sensitivity, whereas the PSMBA shell layer was used to improve the stability of the unimolecular micelles. The PDS exhibited a spherical structure with the size of 10-20 nm at pH 7.4. PDS micelles had excellent stability to resist the large volume liquid dilution. Moreover, it exhibited excellent stability in a complex biological microenvironment because of a superhigh antiprotein adhesion capacity of the PSBMA shell layer compared with PAMAM micelles. Drug release studies confirmed that the DOX can remain in the PDS micelles at pH 7.4 and 37 °C, whereas it can rapidly be released when the pH decreases to 5.0 and/or the temperature increases to 40 °C. In vitro studies suggested that the PDS drug delivery system can effectivity induce apoptosis and inhibit the proliferation of cancer cells. In vivo studies suggested that the PDS micelles prolonged the circulation time, decreased the side effects, and increased the antitumor efficacy. Therefore, the prepared PDS micelles are a potential anticancer drug delivery carrier for cancer therapy.

Biocompatible Dendrimer-Encapsulated Palladium Nanoparticles for Oxidation of Morin

Development of highly efficient catalysts to expedite the degradation of organic dyes has been drawing great attention. The aggregation of catalysts reduces the accessibility of catalytic centers for organic dyes and therefore decreases their catalytic ability. Herein, we report a facile method to prepare highly biocompatible and stable dendrimer-encapsulated palladium nanoparticles (Pd n -G5MCI NPs), which exhibit high catalytic efficiency for oxidation of morin. The biocompatible dendrimers were prepared via surface modification of G5 polyamidoamine (G5 PAMAM) dendrimers using maleic anhydride and l-cysteine. Then, they were incubated with disodium tetrachloropalladate, followed by reduction using sodium borohydride to generate Pd n -G5MCI NPs. Transmission electron microscopy results demonstrated that palladium nanoparticles (Pd NPs) inside Pd n -G5MCI had small diameters (1.77-2.35 nm) and monodisperse states. Dynamic light scattering results confirmed that Pd n -G5MCI NPs had good dispersion and high stability in water. Furthermore, MTT results demonstrated that Pd n -G5MCI NPs had high biocompatibility. More importantly, Pd n -G5MCI NPs successfully catalyzed the decomposition of H2O2 to the hydroxyl radical (•OH), and the generated •OH quickly oxidized morin. This reaction kinetics followed pseudo-first-order kinetics. Apparent rate constant (k app) is an important criterion for evaluating the catalytic rate. The concentrations of Pd n -G5MCI NPs and H2O2 were positively correlated with k app, whereas the correlation between the concentration of morin and k app was negative. The prepared Pd n -G5MCI NPs have great potential to catalyze the degradation of organic dyes in bio-related systems in the future.

Zwitterion-functionalized dendrimer-entrapped gold nanoparticles for serum-enhanced gene delivery to inhibit cancer cell metastasis

We demonstrate a novel serum-enhanced gene delivery approach using zwitterion-functionalized dendrimer-entrapped gold nanoparticles (Au DENPs) as a non-viral vector for inhibition of cancer cell metastasis in vitro. Poly(amidoamine) dendrimers of generation 5 decorated with zwitterion carboxybetaine acrylamide (CBAA) and lysosome-targeting agent morpholine (Mor) were utilized to entrap gold NPs. We show that both Mor-modified and Mor-free Au DENPs are cytocompatible and can effectively deliver plasmid DNA encoding different reporter genes to cancer cells in medium with or without serum. Strikingly, due to the antifouling property exerted by the attached zwitterion CBAA, the gene delivery efficiency of Mor-modified Au DENPs and the Mor-free Au DENPs in the serum-containing medium are 1.4 and 1.7 times higher than the corresponding vector in serum-free medium, respectively. In addition, the Mor-free vector has a better gene expression efficiency than the Mor-modified one although the Mor modification enables the polyplexes to have enhanced cancer cell uptake. Wound healing and hypermethylated in cancer 1 (HIC1) protein expression assay data reveal that the expression of HIC1 gene in cancer cells enables effective inhibition of cell migration. Our findings suggest that the created zwitterion-functionalized Au DENPs may be employed as a powerful vector for serum-enhanced gene therapy of different diseases. STATEMENT OF SIGNIFICANCE: One major challenge in the non-viral gene delivery system is that the strong interaction between serum protein and the positively charged vector/gene polyplexes neutralize the positive charge of the polyplexes and form possible protein corona, thereby significantly reducing their cellular uptake efficiency and subsequent gene transfection outcome. Here we demonstrate the conceptual advances in the serum-enhanced gene delivery using zwitterionic modification of polycationic poly(amidoamine) (PAMAM) dendrimer-entrapped gold nanoparticles (Au DENPs). We demonstrate that partial zwitterionic modification of Au DENPs is able to confer them with antifouling property to resist serum protein adsorption. Hence the vector/DNA polyplexes are able to maintain their positive potentials and small hydrodynamic size in the serum environment, where serum solely play the role as a nutrition factor for enhanced gene delivery. We demonstrate that partial modification of zwitterion carboxybetaine acrylamide (CBAA) and morpholine (Mor) onto the surface Au DENPs renders the vector with both antifouling property and lysosome targeting ability, respectively. The generated functional Au DENPs can compact pDNA to form polyplexes that enable serum-enhanced gene expression. In particular, once complexed with hypermethylated in cancer 1 (HIC1) gene, the polyplexes can significantly inhibit cancer cell migration and metastasis.

Design, Synthesis, and Characterization of Fully Zwitterionic, Functionalized Dendrimers

Dendrimers are interesting candidates for various applications because of the high level of control over their architecture, the presence of internal cavities, and the possibility for multivalent interactions. More specifically, zwitterionic dendrimers modified with an equal number of oppositely charged groups have found use in in vivo biomedical applications. However, the design and control over the synthesis of these dendrimers remains challenging, in particular with respect to achieving full modification of the dendrimer. In this work, we show the design and subsequent synthesis of dendrimers that are highly charged while having zero net charge, that is zwitterionic dendrimers that are potential candidates for biomedical applications. First, we designed and fully optimized the synthesis of charge-neutral carboxybetaine and sulfobetaine zwitterionic dendrimers. Following their synthesis, the various zwitterionic dendrimers were extensively characterized. In this study, we also report for the first time the use of X-ray photoelectron spectroscopy as an easy-to-use and quantitative tool for the compositional analysis of this type of macromolecules that can complement techniques such as nuclear magnetic resonance and gel permeation chromatography. Finally, we designed and synthesized zwitterionic dendrimers that contain a variable number of alkyne and azide groups that allow straightforward (bio)functionalization via click chemistry.

Highly biocompatible zwitterionic dendrimer-encapsulated platinum nanoparticles for sensitive detection of glucose in complex medium

The sensitive detection of glucose using zwitterionic dendrimer-encapsulated platinum nanoparticles was not affected by proteins.

Enhanced glucose detection using dendrimer encapsulated gold nanoparticles benefiting from their zwitterionic surface

The application of ultrasmall gold nanoparticles as enzyme mimics has been drawing great attention. Herein, we developed zwitterionic dendrimer encapsulated gold nanoparticles (Au-G5MC NPs) for highly sensitive and simple colorimetric detection of glucose. Au-G5MC NPs showed peroxidase-like property, which could efficiently catalyze oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂, producing a blue color product (oxTMB). This peroxidase-like reaction follows a typical Michaelis-Menten kinetics. The K_m towards TMB exhibited a lower value (0.194 mM) than that of horseradish peroxidase (HRP, 0.434 mM). Furthermore, the peroxidase-like properties of Au-G5MC NPs enable colorimetric detection of the concentration of glucose with high selectivity. The linear concentration range of this method was from 14 μM to 166 μM with the detection limit down to 3.8 μM. More importantly, the detection was not interfered by proteins due to the single zwitterionic layer on the Au-G5MC NPs surface. These excellent properties are attributed to the ultrasmall size of gold nanoparticles and high stability of Au-G5MC NPs in complex medium. This catalytic system might have great potential applications for glucose detection in medical diagnostics and biochemistry in the future.

Toxicology of Engineered Nanoparticles: Focus on Poly(amidoamine) Dendrimers

Engineered nanomaterials are increasingly being developed for paints, sunscreens, cosmetics, industrial lubricants, tyres, semiconductor devices, and also for biomedical applications such as in diagnostics, therapeutics, and contrast agents. As a result, nanomaterials are being manufactured, transported, and used in larger and larger quantities, and potential impacts on environmental and human health have been raised. Poly(amidoamine) (PAMAM) dendrimers are specifically suitable for biomedical applications. They are well-defined nanoscale molecules which contain a 2-carbon ethylenediamine core and primary amine groups at the surface. The systematically variable structural architecture and the large internal free volume make these dendrimers an attractive option for drug delivery and other biomedical applications. Due to the wide range of applications, the Organisation for Economic Co-Operation and Development (OECD) have included them in their list of nanoparticles which require toxicological assessment. Thus, the toxicological impact of these PAMAM dendrimers on human health and the environment is a matter of concern. In this review, the potential toxicological impact of PAMAM dendrimers on human health and environment is assessed, highlighting work to date exploring the toxicological effects of PAMAM dendrimers.

Highly stable and biocompatible zwitterionic dendrimer-encapsulated palladium nanoparticles that maintain their catalytic activity in bacterial solution

This study offers a method for constructing an artificial enzyme (Pd_n-G5MC), which maintains its catalytic efficiency in bacterial solution.

Biodegradable zwitterionic sulfobetaine polymer and its conjugate with paclitaxel for sustained drug delivery

A fully biodegradable zwitterionic polymer and the corresponding conjugate with paclitaxel (PTX) were synthesized as promising biomaterials. Allyl-functionalized polylactide (PLA) was employed as the precursor of polymer backbones. UV-induced thiol-ene reaction was conducted to conjugate thiol-functionalized sulfobetaine (SB) with the PLA-based backbone. The resulting zwitterionic polymer did not exhibit considerable cytotoxicity. A polymer-drug conjugate was also obtained by thiol-ene reaction of both thiol-functionalized SB and PTX with allyl-functionalized PLA. The conjugate could readily form narrowly-dispersed nanoparticles in aqueous solutions with a volume-average hydrodynamic diameter (Dh,V) of 19.3 ± 0.2 nm. Such a polymer-drug conjugate-based drug delivery system showed full degradability, well-suppressed non-specific interaction with biomolecules, and sustained drug release. In vitro assessments also confirmed the significant anti-cancer efficacy of the conjugate. After 72 h incubation with PLA-SB/PTX containing 10 µg/mL of PTX, the cell viabilities of A549, MCF7, and PaCa-2 cells were as low as 20.0 ± 2.5%, 1.7 ± 1.7%, and 14.8 ± 0.9%, respectively. Both flow cytometry and confocal microscopy suggested that the conjugates could be easily uptaken by A549 cells before the major release of PTX moieties. Overall, this work elucidates promising potentials of biodegradable zwitterionic polymer-based materials in biomedical applications.

STATEMENT OF SIGNIFICANCE

The applicability of FDA-approved biodegradable aliphatic polyesters has been significantly restricted because they are hydrophobic and lack functionalities. Recently zwitterionic polymers have emerged as promising hydrophilic biomaterials, but most of the reported zwitterionic polymers are non-biodegradable. This study reports a novel aliphatic polyester-based zwitterionic polymer and the corresponding polymer-drug conjugate. Their aliphatic polyester and zwitterionic components provide them with high enzymatic degradability and low nonspecific interactions with biomolecules, respectively. While the zwitterionic polymer did not show noticeable cytotoxicity, the corresponding polymer-anticancer drug conjugate exhibited acid-sensitive sustained drug release, remarkable effectiveness in killing cancer cells, as well as the ready cellular internalization. This work lays a foundation for the further development of synthetic biodegradable zwitterionic polymer-based materials which potentially may have broad and significant biomedical applications.

Dendrimers meet zwitterions: development of a unique antifouling nanoplatform for enhanced blood pool, lymph node and tumor CT imaging

We report the synthesis and characterization of antifouling zwitterion carboxybetaine acrylamide (CBAA)-modified dendrimer-entrapped gold nanoparticles (Au DENPs) for enhanced CT imaging applications. The CBAA-modified nanodevice displays a better protein resistance property, less macrophage cellular uptake and liver accumulation, and longer blood half-delay time than the PEGylated counterpart material, thereby enabling enhanced blood pool, lymph node, and tumor CT imaging.

A multifunctional polyethylenimine-based nanoplatform for targeted anticancer drug delivery to tumors in vivo

The development of cost-effective targeted drug delivery systems for cancer chemotherapy still remains a great challenging task. Here, we describe the synthesis and characterization of multifunctional polyethylenimine (PEI) as an effective vehicle to load an anticancer drug doxorubicin (DOX) for in vivo targeted cancer therapy. In this study, PEI was sequentially conjugated with polyethylene glycol (PEG) monomethyl ether, PEGylated folic acid (FA), and fluorescein isothiocyanate (FI). This was followed by the acetylation of the remaining PEI surface amines. The formed FA-targeted multifunctional PEI (FA-mPEI) was used as a vehicle to encapsulate DOX. We show that the formed FA-mPEI/DOX complexes with each PEI encapsulating 6.9 DOX molecules are water dispersible and can sustainably release DOX in a pH-dependent manner, showing a higher release rate under acidic pH conditions than under physiological pH conditions. Furthermore, the complexes display specific therapeutic efficacy to cancer cells in vitro and a subcutaneous tumor model in vivo, and have good organ compatibility. The designed multifunctional PEI may be used as an effective vehicle for targeted cancer chemotherapy.

Highly stable and biocompatible dendrimer-encapsulated gold nanoparticle catalysts for the reduction of 4-nitrophenol

The enhanced properties of dendrimer-encapsulated gold nanoparticles were attributed to the single zwitterionic layer on the new dendrimer template.

Rapid and efficient magnetization of mesenchymal stem cells by dendrimer-functionalized magnetic nanoparticles

Aim: Rapid and efficient magnetization of human bone marrow stromal cells (BMSC) through functionalized magnetic nanoparticles (MNP). Methods: MNP were functionalized with poly(epsilon-lysine) dendrons exposing carboxybetaine residue (CB-MNP) to enhance binding to the cellular glycocalix. BMSC were incubated with CB-MNP or non-functionalized PAA-MNP for 5–30 min in suspension. Results: CB-MNP functionalization increased the magnetization efficiency by threefold. Remarkably, 66% of cells were magnetized after only 5 min and the maximum efficiency of >80% was reached by 15 min. BMSC viability, proliferation and differentiation were not impaired: actually, adipogenic and osteogenic differentiation were even improved. Conclusion: Carboxybetaine-dendron functionalization ensured rapid and efficient BMSC magnetization and allowed innovative suspension labeling, with a potential for bypassing adhesion culture of progenitors for regenerative medicine.

Development of Long-Circulating Zwitterionic Cross-Linked Micelles for Active-Targeted Drug Delivery

Blood stability, active targeting, and controlled drug release are the most important features to design desirable drug carriers. Here, we demonstrate a zwitterionic biodegradable cross-linked micelle based on a penta-block copolymer, which utilizes poly(carboxybetaine methacrylate) as hydrophilic segment, poly(ε-caprolactone) as biodegradable hydrophobic segment, poly(S-2-hydroxyethyl-O-ethyl dithiocarbonate methacrylate) (PSODMA) block as thiol protecting segment for cross-linking, and cyclic Arg-Gly-Asp-d-Tyr-Lys [c(RGDyK)] as targeting ligand. As a result, this micelle possessed excellent colloidal stability at high dilution and in 50% fetal bovine serum. In vitro drug release experiment showed no burst release under physiological conditions but accelerated drug release in mimicking tumor tissue environment. In vivo tests showed that the drug-loaded micelles had prolonged half-life in bloodstream, enhanced therapeutic efficiency, and reduced cardiac toxicity and biotoxicity compared with free drug formulation. Taken together, the reported c(RGDyK)-modified zwitterionic interfacially cross-linked micelle has emerged as an appealing platform for cancer therapy.

Gd-Chelated poly(propylene imine) dendrimers with densely organized maltose shells for enhanced MR imaging applications

Gd-Chelated fourth generation poly(propylene imine) dendrimers with densely organized maltose shells can be designed for enhanced MR imaging applications.

Stable and pH-responsive polyamidoamine based unimolecular micelles capped with a zwitterionic polymer shell for anticancer drug delivery

Zwitterionic dendrimer based unimolecular micelles for anticancer drug delivery were prepared, exhibiting excellent stability in complex biological media.

Zwitterionic amphiphile coated magnetofluorescent nanoparticles - synthesis, characterization and tumor cell targeting

Magnetofluorescent nanoparticles (MFNPs) have recently attracted significant research interests due to their potential applications in biological manipulation and imaging. In this work, through a simple and fast self-assembling process, we first report the preparation of zwitterionic MFNPs (ZW-MFNPs) in the form of micelles using our newly synthesized zwitterionic amphiphiles, CuInS2/ZnS quantum dots, and MnFe2O4 magnetic nanoparticles. ZW-MFNPs integrate both MnFe2O4 magnetic nanoparticles and CuInS2/ZnS quantum dots in their hydrophobic cores and zwitterionic groups such as carboxybetaine and sulfobetaine on their hydrophilic shells. ZW-MFNPs possess dual imaging properties, high (Mn + Fe) recovery, excellent stability in aqueous solutions with a wide pH/ionic-strength range and physiological media, minimal cytotoxicity, and specific targeting to brain tumor cells after bioconjugation with chlorotoxin. The unique characteristics of ZW-MFNPs may open an avenue for these particles to be employed in broad biomedical applications.

A study on the hemocompatibility of dendronized chitosan derivatives in red blood cells

Dendrimers are hyperbranched macromolecules with well-defined topological structures and multivalent functionalization sites, but they may cause cytotoxicity due to the presence of cationic charge. Recently, we have introduced alkyne-terminated poly(amidoamine) (PAMAM) dendrons of different generations (G=2,3) into chitosan to obtain dendronized chitosan derivatives [Cs-g-PAMAM (G=2,3)], which exhibited a better water solubility and enhanced plasmid DNA transfection efficiency. In this study, we attempted to examine the impact of Cs-g-PAMAM (G=2,3) at different concentrations (25 μg/mL, 50 μg/mL, and 100 μg/mL) on the morphology, surface structure, and viability of rat red blood cells (RBCs). The results showed that treatment of RBCs with Cs-g-PAMAM (G=2,3) at 50 μg/mL and 100 μg/mL induced a slightly higher hemolysis than Cs, and Cs-g-PAMAM (G=3) caused a slightly higher hemolysis than Cs-g-PAMAM (G=2), but all values were <5.0%. Optical microscopic and atomic force microscopic examinations indicated that Cs-g-PAMAM (G=2,3) caused slight RBC aggregation and lysis. Treatment of RBCs with 100 μg/mL Cs-g-PAMAM (G=3) induced echinocytic transformation, and RBCs displayed characteristic irregular contour due to the folding of the periphery. Drephanocyte-like RBCs were observed when treated with 100 μg/mL Cs-g-PAMAM (G=3). Erythrocytes underwent similar shape transition upon treatment with Cs-g-PAMAM (G=2) or Cs. The roughness values (Rms) of RBCs incubated with Cs-g-PAMAM (G=2,3) were significantly larger than those for RBCs incubated with physiological saline (P<0.01), but the Rms showed no difference for Cs and Cs-g-PAMAM (G=2,3) (P>0.05). Furthermore, Cs-g-PAMAM (G=2,3) exhibited a lower cytotoxicity in human kidney 293T cells. These results indicate that Cs-g-PAMAM (G=2,3) are hemocompatible but may disturb membrane and lipid structures at higher concentrations. Further safety and biocompatibility evaluations are warranted for Cs-g-PAMAM. Our findings prove helpful for a better understanding of the advantages of combining PAMAM dendrimers and chitosan to design and develop new, safe, and effective drug delivery vehicles.

A series of codendrimers from polyamidoamine (PAMAM) and oligoethylene glycols (OEG) dendrons as drug carriers: the effect of OEG dendron decoration degree

To evaluate the effect of OEG dendron decoration degree and find a suitable carrier, a series of codendrimers are prepared and utilized to transport methotrexate.

Preparation of magnetic pH-sensitive microcapsules with an alginate base as colon specific drug delivery systems through an entirely green route

The aim of this work was to prepare pH-sensitive drug carriers for colon specific drug delivery through a completely green and environmentally friendly route (without using any organic solvents, hazardous chemicals and even a harsh procedure).

Synthesis and characterization of dendritic star-shaped zwitterionic polymers as novel anticancer drug delivery carriers

In this work, a novel dendritic star-shaped zwitterionic polymer, polyamidoamine-graft-poly[3-dimethyl (methacryloyloxyethyl) ammonium propanesulfonate] (PAMAM-g-PDMAPS), was synthesized. PAMAM dendrimers (generation 2, G2) were firstly prepared and then converted into the PAMAM-Br macroinitiator with 2-bromoisobutyryl bromide for ATRP. Finally, ATRP of zwitterionic DMAPS was carried out to obtain the dendritic star-shaped polymers PAMAM-g-PDMAPS with different PDMAPS chain lengths. Fourier transform-infrared spectroscopy, (1)H NMR, dynamic laser light scattering (DLS), and TEM were used to characterize the polymers. Encapsulation of adriamycin (ADR) by PAMAM-g-PDMAPS nanoparticles and ADR release behavior from ADR-loaded PAMAM-g-PDMAPS nanoparticles were investigated in detail. PAMAM-g-PDMAPS polymers, even starting from low-generation PAMAM core (G2), were found to show high loading efficiency for ADR because ADR existed not only within G2 PAMAM cores but also in PDMAPS layers. The release profile of ADR from ADR-loaded PAMAM-g-PDMAPS nanoparticles was pH-sensitive and could be controlled by the length of PDMAPS chains. Cell viability studies indicated that ADR-loaded PAMAM-g-PDMAPS could effectively restrain the growth of HepG2 cells and even kill them, whereas PAMAM-g-PDMAPS exhibited nontoxicity. All these results demonstrated that dendritic star-shaped zwitterionic polymers PAMAM-g-PDMAPS are attractive candidates as anticancer drug delivery carriers.

The role of autophagy in the neurotoxicity of cationic PAMAM dendrimers

Poly(amidoamine) (PAMAM) dendrimers, are among the most common classes of dendrimers that are intended for a wide range of biomedical applications and extensively investigated for brain-specific drug delivery, imaging and diagnosis. Unfortunately, neurotoxicity of PAMAM dendrimers, the underlying mechanism of which is poorly-elucidated, poses a far-reaching challenge to their practical applications. In this study, we reported that PAMAM dendrimers induced both cytotoxicity and autophagic flux in a panel of human glioma cell lines. Meanwhile, inhibition of autophagy significantly reversed cell death caused by PAMAM dendrimers, indicating the cytotoxic role of autophagy in neurotoxicity caused by PAMAM dendrimers. Akt/mTOR pathway was most likely to participate in initiation of PAMAM dendrimers-induced autophagy. Moreover, autophagy induced by PAMAM dendrimers might be partially mediated by intracellular ROS generation. Collectively, these data elucidated the critical role of autophagy in neurotoxicity associated with exposure to cationic PAMAM dendrimers in vitro, raising concerns about possible neurotoxic reaction caused by future clinical applications of PAMAM dendrimers and providing potential strategies to ameliorate toxic effects of PAMAM dendrimers.

Co-caged gold nanoclusters and methyl motifs lead to detoxification of dendrimers and allow cytosolic access for siRNA transfection

A simple co-caging strategy for siRNA transfection is reported that focuses on overcoming the two limitations of dendrimers – inherent toxicity and inefficient cytosolic access.