Surface Chemistry of Biodegradable Polymers for Drug Delivery Systems

Steric and chelating ring concerns on the l-lactide polymerization by asymmetric β-diketiminato zinc complexes

Asymmetric β-diketiminato zinc complexes were investigated in l-lactide polymerization. The catalytic rate depended heavily on the N-aryl substituents.

Bis(amido) rare-earth complexes coordinated by tridentate amidinate ligand: synthesis, structure and catalytic activity in the polymerization of isoprene and rac-lactide

Rare-earth bis(amides) {2-[Ph₂Р(O)]C₆H₄NC(tBu)N(2,6-Me₂C₆H₃)}Ln(N(SiMe₃)₂)₂ (Ln = Y, Nd, La) coordinated by tridentate amidinate ligand were synthesized, structurally characterized and evaluated as catalysts for isoprene and rac-lactide polymerizations.

Self-Assembling Monomeric Nucleoside Molecular Nanoparticles Loaded with 5-FU Enhancing Therapeutic Efficacy against Oral Cancer

Conventional oligonucleotide based drug delivery systems suffer from lengthy synthetic protocols, high cost, and poor chemical or enzymatic stability under certain circumstances. Canonical free individual nucleosides cannot form stable nanostructures in aqueous solution as drug vehicles. Here, we report the development of a monomeric self-assembled nucleoside nanoparticle (SNNP) into an efficient drug delivery system which has currently no parallel in such field. This was achieved using a l-configurational pyrimido[4,5-d]pyrimidine nucleoside building block that can form robust discrete nanoparticles in just one step with water as the sole solvent. Its high biocompatibility and low toxicity was demonstrated in vitro and in vivo. In mouse xenograft model of oral squamous cell carcinoma (OSCC), SNNP loaded with 5-fluoro-uracile (5-FU-SNNP) remarkably retarded the tumor growth compared with free 5-FU, albeit SNNP alone showed no antitumor effect. The stability in blood circulation and the effective concentration of 5-FU in tumor tissue were increased upon the loading with SNNP. TUNEL and immunohistochemistry analyses further indicated that the superior in vivo antitumor efficacy of 5-FU-SNNP compared to free 5-FU was associated with an enhanced degree of inhibition of cell proliferation and stimulation of cell apoptosis. Furthermore, SNNP alleviated the toxic side effects of 5-FU. These findings suggested that when loaded with SNNP, 5-FU has better antitumor efficacy and lower side effects, indicating that SNNP can efficiently act as a readily accessible, robust, biocompatible and low-toxic nanobiomaterial which may find wide therapeutic applications clinically in the future.

Antimicrobial Activity Evaluation on Silver Doped Hydroxyapatite/Polydimethylsiloxane Composite Layer

The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pressure corona discharges. Finally, the new silver doped hydroxyapatite/polydimethylsiloxane composite layer has been obtained by the thermal evaporation technique. The Ag:HAp-PDMS composite layers were characterized by various techniques, such as Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity of the Ag:HAp-PDMS composite layer was assessed against Candida albicans ATCC 10231 (ATCC-American Type Culture Collection) by culture based and confirmed by SEM and Confocal Laser Scanning Microscopy (CLSM) methods. This is the first study reporting the antimicrobial effect of the Ag:HAp-PDMS composite layer, which proved to be active against Candida albicans biofilm embedded cells.

Design of a micellized α-cyclodextrin based supramolecular hydrogel system

In recent years supramolecular structures built from macrocyclic compounds have attracted tremendous interest due to the unique properties derived from dynamic self-assembly. Our study proposes a two-step mechanism to form a supramolecular hydrogel system: (1) the formation of micelles, and (2) micelle association with α-cyclodextrin (α-CD) due to threading of PEGMA in the α-CD cavity, forming inclusion complexes. Using this mechanism, a supramolecular hydrogel made from a tri-component copolymer PLLA/DMAEMA/PEGMA and α-CD was fabricated for the first time and characterized in terms of its structural, morphological, and rheological properties.

Miniscrews for orthodontic anchorage: nanoscale chemical surface analyses

OBJECTIVES

The goal of this study was to determine the chemical composition of the passivation layer of three clinically available orthodontic miniscrews at different depths.

MATERIALS AND METHODS

The miniscrews used were Aarhus Mini-Implant (AAR), IMTEC Ortho (IMT), and VectorTAS (VEC). The chemical compositions of the as-received miniscrews were determined by X-ray photoelectron spectroscopy (XPS). Data was acquired before etching the miniscrews with argon, as well as after etching at depths of 10 nm, 20 nm, 30 nm, and 80 nm.

RESULTS

The elements found in all miniscrews were mainly C, O, and Ti. Also found were other metals in small amounts, and other trace elements. All three miniscrews showed very different characteristics in surface composition. IMT had the greatest increase in Ti, as well as the most titanium metal at 80 nm. VEC remained stable at all tested depths and contained no titanium metal at 80 nm. AAR was an intermediate between the two.

CONCLUSIONS

The passivation layer of the orthodontic miniscrews has different compositions depending on the brand, as well as the depth analyzed. VEC appeared to have the largest passivation layer, and IMT appeared to have the thinnest passivation layer.

Biodegradable micelles capable of mannose-mediated targeted drug delivery to cancer cells

A targeted micellar drug delivery system is developed from a biocompatible and biodegradable amphiphilic polyester, poly(Lac-OCA)-b-(poly(Tyr(alkynyl)-OCA)-g-mannose) (PLA-b-(PTA-g-mannose), that is synthesized via controlled ring-opening polymerization of O-carboxyanhydride (OCA) and highly efficient "Click" chemistry. Doxorubicin (DOX), a model lipophilic anticancer drug, can be effectively encapsulated into the micelles, and the mannose moiety allows active targeting of the micelles to cancer cells that specifically express mannose receptors, which thereafter enhances the anticancer efficiency of the drug. Comprised entirely of biodegradable and biocompatible polyesters, this micellar system demonstrates promising potentials for targeted drug delivery and cancer therapy.

Synthesis and characterization of rare-earth metal complexes supported by a new pentadentate Schiff base and their application in heteroselective polymerization of rac-lactide

Both rare-earth metal salen aryloxides and amides can efficiently initiate the ring-opening polymerization of rac-lactide to give heterotactic-rich polylactides.

Comparing l-lactide and ε-caprolactone polymerization by using aluminum complexes bearing ketiminate ligands: steric, electronic, and chelating effects

Herein, the l-lactide polymerization rate of a series of Al complexes bearing ketimine ligands was investigated, and the polymerization characteristics between l-lactide and ε-caprolactone were compared.

Comparative study of ring-opening polymerization of l-lactide and ε-caprolactone using zirconium hexadentate bis(aminophenolate) complexes as catalysts

A series of zirconium bis(aminophenolate) complexes as catalysts for the ring opening polymerization of l-lactide (LA) and ε-caprolactone (CL) were investigated.

Cellulose nanofiber–titania nanocomposites as potential drug delivery systems for dermal applications

Nanocomposites with potential for dermal drug delivery have been developed using nanotitania chemically grafted onto nanocellulose as an active ingredient for enhanced uptake and controlled release of model drug loads.

Biocompatible succinic acid-based polyesters for potential biomedical applications: fungal biofilm inhibition and mesenchymal stem cell growth

Poly(alkene succinates) are promising materials for specialized medical devices and tissue engineering, presenting intrinsic properties, such as; fungal biofilm inhibition, biocompatibility and stem cells controlled growth promotion.

A closer look at ε-caprolactone polymerization catalyzed by alkyl aluminum complexes: the effect of induction period on overall catalytic activity

Previous studies on the ring-opening polymerization of ε-caprolactone using structurally related aluminum complexes as pre-catalysts showed inconsistent trends in the total conversion time.

Fabrication of single-hole glutathione-responsive degradable hollow silica nanoparticles for drug delivery

In the present study, a kind of single-hole glutathione (GSH)-responsive degradable hollow silica nanoparticles (G-DHSNs) was synthesized and used as carriers of doxorubicin (DOX) (DOX-G-DHSNs). The G-DHSNs were accurately designed and fabricated with a simple and convenient method, and without any extra pernicious component. The composition, morphology and properties of the G-DHSNs had been characterized by (1)HNMR spectra, Fourier transform infrared spectrograph, thermo gravimetric analysis, transmission electron microscope, and scanning electron microscope. The degradation study of G-DHSNs showed that the G-DHSNs would be broken into pieces after interacting with GSH. Besides, the negligible hemolytic activity and low cytotoxicity of the G-DHSNs demonstrated its excellent biocompatibility. pH- and GSH-triggered release of DOX followed by the decomposition of G-DHSNs within TCA8113 cancer cells was further confirmed by flow cytometry and confocal laser scanning microscopy studies. All of these results indicated that G-DHSNs can be used as safe and promising drug nanocarriers.

Drug delivery vehicles on a nano-engineering perspective

Nanoengineered drug delivery systems (nDDS) have been successfully used as clinical tools for not only modulation of pharmacological drug release profile but also specific targeting of diseased tissues. Until now, encapsulation of anti-cancer molecules such as paclitaxel, vincristin and doxorubicin has been the main target of nDDS, whereby liposomes and polymer-drug conjugates remained as the most popular group of nDDS used for this purpose. The success reached by these nanocarriers can be imitated by careful selection and optimization of the different factors that affect drug release profile (i.e. type of biomaterial, size, system architecture, and biodegradability mechanisms) along with the selection of an appropriate manufacture technique that does not compromise the desired release profile, while it also offers possibilities to scale up for future industrialization. This review focuses from an engineering perspective on the different parameters that should be considered before and during the design of new nDDS, and the different manufacturing techniques available, in such a way to ensure success in clinical application.

Hydration structures of lactic acid: characterization of the ionic clathrate hydrate formed with a biological organic acid anion

Lactic acid is incorporated in the ionic clathrate hydrate showing various water clustering patterns.

Dual drug-eluting stents coated with multilayers of hydrophobic heparin and sirolimus

Polymer coatings for stents are considered one of the key factors that lead to adverse cardiac events after coronary arterial stenting. This study presents a dual drug-eluting stent (DES) that is coated with multilayers of Duraflo heparin and sirolimus but containing no other organic polymers. The hydrophobic Duraflo heparin coating was used to improve the hemocompatibility of the stent and serve as a drug reservoir for the controlled release of sirolimus, thus avoiding inflammatory reactions induced by the conventional polymers. The Duraflo heparin and sirolimus were coated layer-by-layer onto the stent surface using a homemade spray-coating device. The drug loading amount can be easily controlled by adjusting the numbers of layers applied and the concentration of the drug solution, indicating the developed coating process is reproducible and well-controlled. After balloon expansion, the coating did not crack or peel off, which demonstrates that the sirolimus/Duraflo heparin coating layers tightly adhere to the stent surface. The activated partial thromboplastin time (APTT) assay showed that the Duraflo heparin coating significantly prolonged the APTT from 27.3 ± 0.3 s to 69.7 ± 6.2 s, demonstrating the anticoagulant ability of the coated stents. The dual DES exhibited a nearly linear sustained-release profile of Duraflo heparin and an initial burst release followed by a slow release of sirolimus. Less than 15% of heparin was released from the DES within 14 days, indicating the stent can maintain its antithrombotic surface for a long time. Because of the layer-by-layer structure, the most outer layer of Duraflo heparin coating may act as a diffusion barrier to retard sirolimus release from the stent. These results confirm that the dual DESs enable simultaneous delivery of antithrombotic and antiproliferative drugs and have potential for the treatment of coronary artery disease.

SiO2@YBO3:Eu3+ hollow mesoporous spheres for drug delivery vehicle

A novel bifunctional (fluorescent, mesoporous) hollow sphere was prepared by coating luminescent YBO3:Eu(3+) nanoparticles onto uniform hollow mesoporous silica spheres (HMSs), derived from an etching strategy using spherical Fe3O4 as templates. The composites exhibit typical mesoporous shells, large interior space, high surface area, and well dispersed nanospheres with controlled size. In addition, the textural properties including the specific surface and pore volume can be easily altered by simply tuning of the spherical Fe3O4 cores. Upon ultraviolet (UV) excitation, the composite shows the characteristic (5)D0-(7)F1-4 red emission lines of Eu(3+) even after loading of the model drug. The composite with a large surface area and cavity was used as the host for loading the anticancer drug doxorubicin hydrochloride (DOX). It is observed that the multifunctional composites exhibit an obvious sustained release property and released in texture- and pH-sensitive patterns. Particularly, the down-conversion (DC) fluorescence intensity of the bifunctional vehicle increases with the release of drug molecules, making it possible to track the position and the drug release amount of the drug carrier system and to detect them by the change of fluorescence intensity.

Computer-Aided 4D Modeling of Hydrolytic Degradation in Micropatterned Bioresorbable Membranes

Real-time degradation studies of bioresorbable polymers can take weeks, months, and even years to conduct. For this reason, developing and validating mathematical models that describe and predict degradation can provide a means to accelerate the development of materials and devices for controlled drug release. This study aims to develop and experimentally validate a computer-aided model that simulates the hydrolytic degradation kinetics of bioresorbable polymeric micropatterned membranes for tissue engineering applications. Specifically, the model applies to circumstances that are conducive for the polymer to undergo surface erosion. The developed model provides a simulation tool enabling the prediction and visualization of the dynamic geometry of the degrading membrane. In order to validate the model, micropatterned polymeric membranes were hydrolytically degraded in vitro and the morphological changes were analyzed using optical microscopy. The model is then extended to predict spatiotemporal degradation kinetics of variational micropatterned architectures.

Redox-Responsive, Core Cross-Linked Polyester Micelles

Monomethoxy poly(ethylene glycol)-b-poly(Tyr(alkynyl)-OCA), a biodegradable amphiphilic block copolymer, was synthesized by means of ring-opening polymerization of 5-(4-(prop-2-yn-1-yloxy)benzyl)-1,3-dioxolane-2,4-dione (Tyr(alkynyl)-OCA) and used to prepare core cross-linked polyester micelles via click chemistry. Core cross-linking not only improved the structural stability of the micelles but also allowed controlled release of cargo molecules in response to the reducing reagent. This new class of core cross-linked micelles can potentially be used in controlled release and drug delivery applications.

Cascade Molecule-Particle-Molecule Self-Assemblies for Fabricating Narrowly Size-Distributed Polymeric Superparticles with a Bicontinuous Nanostructure

Broader developments of nanoscience and nanotechnology require complexly but regularly structured nanoparticles whose fabrications in turn pose a great challenge to nanoscience and nanotechnology. In this communication, we report a new and robust method with a clear mechanism for fabricating narrowly size-distributed superparticles with a bicontinuous inner structure. The processes for the fabrication include: molecular self-assembly of a triblock copolymer in its selective solvent into the core-shell-corona micelles, the self-limited aggregation of the micelles (particles) into narrowly size-distributed superparticles constructed by the integrated micelles, and the final molecular self-assembly confined within the superparticles into cylinders that are crowded and interconnected to form the bicontinuous nanostructure; the molecular self-assembly into the micelles, the self-limited aggregation of the particles (i.e., the micelles), and the further molecular self-assembly within the superparticles occurred in a cascade manner.

Tris(1,2-dimeth-oxy-ethane-κO,O')iodidocalcium iodide

In the title complex, [CaI(C(4)H(10)O(2))(3)]I, the Ca(II) atom is seven-coordinated by six O atoms from three 1,2-dimeth-oxy-ethane (DME) ligands and one iodide anion in a distorted penta-gonal-bipyramidal geometry. The I atom and one of the O atoms from a DME ligand lie in the axial positions while the other O atoms lie in the basal plane. The other iodide anion is outside the complex cation.