Biodegradable depsipeptide–PDO–PEG-based block copolymer micelles as nanocarriers for controlled release of doxorubicin

Influence of several biodegradable components added to pure and nanosilver-doped PMMA bone cements on its biological and mechanical properties

Acrylic bone cements (BC) are wildly used in medicine. Despite favorable mechanical properties, processability and inject capability, BC lack bioactivity. To overcome this, we investigated the effects of selected biodegradable additives to create a partially-degradable BC and also we evaluated its combination with nanosilver (AgNp). We hypothesized that using above strategies it would be possible to obtain bioactive BC. The Cemex was used as the base material, modified at 2.5, 5 or 10 wt% with either cellulose, chitosan, magnesium, polydioxanone or tricalcium-phosphate. The resulted modified BC was examined for surface morphology, wettability, porosity, mechanical and nanomechanical properties and cytocompatibility. The composite BC doped with AgNp was also examined for its release and antibacterial properties. The results showed that it is possible to create modified cement and all studied modifiers increased its porosity. Applying the additives slightly decreased BC wettability and mechanical properties, but the positive effect of the additives was observed in nanomechanical research. The relatively poor cytocompatibility of modified BC was attributed to the unreacted monomer release, except for polydioxanone modification which increased cells viability. Furthermore, all additives facilitated AgNp release and increased BC antibacterial effectiveness. Our present studies suggest the optimal content of biodegradable component for BC is 5 wt%. At this content, an improvement in BC porosity is achieved without significant deterioration of BC physical and mechanical properties. Polydioxanone and cellulose seem to be the most promising additives that improve porosity and antibacterial properties of antibiotic or nanosilver-loaded BC. Partially-degradable BC may be a good strategy to improve their antibacterial effectiveness, but some caution is still required regarding their cytocompatibility. STATEMENT OF SIGNIFICANCE: The lack of bone cement bioactivity is the main limitation of its effectiveness in medicine. To overcome this, we have created composite cements with partially-degradable properties. We also modified these cements with nanosilver to provide antibacterial properties. We examined five various additives at three different contents to modify a selected bone cement. Our results broaden the knowledge about potential modifiers and properties of composite cements. We selected the optimal content and the most promising additives, and showed that the combination of these additives with nanosilver would increase cements` antibacterial effectiveness. Such modified cements may be a new solution for medical applications.

Amphiphilic block copolymer NPs obtained by coupling ricinoleic acid/sebacic acids and mPEG: Synthesis, characterization, and controlled release of paclitaxel

Currently, nanoparticles (NPs) made of amphiphilic block copolymer are still an essential part of drug delivery system. Here, we report a novel amphiphilic block copolymer and paclitaxel (PTX)-loaded copolymer NPs for the controlled delivery of PTX. The block copolymer was synthesized via melt polycondensation method of methoxy poly(ethylene glycol) (mPEG), sebacic acid (SA) and ricinoleic acid (RA). A series of characterization approaches such as Fourier Transform Infrared Spectroscopy (FTIR), ¹Hydrogen-Nuclear Magnetic Resonance (¹H-NMR), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD) and Gel Permeation Chromatography (GPC) applied have shown that the amphiphilic block copolymer was prepared as designed. NPs prepared by nanoprecipitation method consist of mPEG segments as the hydrophilic shell and RA-SA segments as the hydrophobic core, hydrophobic PTX was encapsulated as model drug. Subsequently, Transmission Electron Microscopy (TEM) analysis indicated that the spherical NPs have effective mean diameters ranging from 100 to 400 nm. Dynamic Light Scattering (DLS) analysis also revealed the controllable NPs diameter by modulating the mass ratio of RA to SA and drug loading amount (DLA). Besides, biphasic profile with zero order drug release was observed in general in vitro release behaviors of PTX from NPs. Further investigation confirmed that the release behaviors depend on the crystallinity of hydrophobic RA-SA segments. Results above suggest that NPs with amphiphlic block copolymer mPEG-b-P(RA-SA)-b-mPEG have a remarkable potential as a carrier for hydrophobic drug delivery in cancer therapy.

Bioreducible, hydrolytically degradable and targeting polymers for gene delivery

Recently, synthetic gene carriers have been intensively developed owing to their promising application in gene therapy and considered as a suitable alternative to viral vectors because of several benefits. But cationic polymers still face some problems like low transfection efficiency, cytotoxicity, and poor cell recognition and internalization. The emerging engineered and smart polymers can respond to some changes in the biological environment like pH change, ionic strength change and redox potential, which is beneficial for cellular uptake. Redox-sensitive disulfide based and hydrolytically degradable cationic polymers serve as gene carriers with excellent transfection efficiency and good biocompatibility owing to degradation in the cytoplasm. Additionally, biodegradable polymeric micelles with cell-targeting function are recently emerging gene carriers, especially for the transfection of endothelial cells. In this review, some strategies for gene carriers based on these bioreducible and hydrolytically degradable polymers will be illustrated.

Mercaptan acids modified amphiphilic copolymers for efficient loading and release of doxorubicin

In this paper, four different kinds of mercaptan acids modified amphiphilic copolymers mPEG-b-PATMC-g-SRCOOH (R=CH₂, CH₂CH₂, (CH₂)₁₀ and CH(COOH)CH₂) were successfully synthesized by thiol-ene "click" reaction between pendent carbon-carbon double bonds of PEG-b-PATMC and thiol groups of thioglycolic acid, 3-mercaptopropionic acid, 11-mercaptoundecanoic acid or 2-mercaptosuccinic acid. DLS and TEM measurements showed that all the mPEG-b-PATMC-g-SRCOOH copolymers could self-assemble to form micelles which dispersed in spherical shape with nano-size before and after DOX loading. The positively-charged DOX could effectively load into copolymer micelles via synergistic hydrophobic and electrostatic interactions. All DOX-loaded mPEG-b-PATMC-g-SRCOOH micelles displayed sustained drug release behavior without an initial burst which could be further adjusted by the conditions of ionic strength and pH. Especially in the case of mPEG-b-PATMC-g-S(CH₂)₁₀COOH (P3) micelles, the suitable hydrophobility and charge density were not only beneficial to improve the DOX-loading efficiency, they were also good for obtaining smaller particle size, higher micelle stability and more timely drug delivery. Confocal laser scanning microscopy (CLSM) and MTT assays further demonstrated efficient cellular uptake of DOX delivered by mPEG-b-PATMC-g-SRCOOH micelles and potent cytotoxic activity against cancer cells.

Multi-targeting peptides for gene carriers with high transfection efficiency

Non-viral gene carriers for gene therapy have been developed for many years.

Electrospun Poly(lactide-co-glycolide-co-3(S)-methyl-morpholine-2,5-dione) Nanofibrous Scaffolds for Tissue Engineering

Biomimetic scaffolds have been investigated in vascular tissue engineering for many years. Excellent biodegradable materials are desired as temporary scaffolds to support cell growth and disappear gradually with the progress of guided tissue regeneration. In the present paper, a series of biodegradable copolymers were synthesized and used to prepared micro/nanofibrous scaffolds for vascular tissue engineering. Poly(lactide-co-glycolide-co-3(S)-methyl-morpholine-2,5-dione) [P(LA-co-GA-co-MMD)] copolymers with different l-lactide (LA), glycolide (GA), and 3(S)-methyl-2,5-morpholinedione (MMD) contents were synthesized using stannous octoate as a catalyst. Moreover, the P(LA-co-GA-co-MMD) nanofibrous scaffolds were prepared by electrospinning technology. The morphology of scaffolds was analyzed by scanning electron microscopy (SEM), and the results showed that the fibers are smooth, regular, and randomly oriented with diameters of 700 ± 100 nm. The weight loss of scaffolds increased significantly with the increasing content of MMD, indicating good biodegradable property of the scaffolds. In addition, the cytocompatibility of electrospun nanofibrous scaffolds was tested by human umbilical vein endothelial cells. It is demonstrated that the cells could attach and proliferate well on P(LA-co-GA-co-MMD) scaffolds and, consequently, form a cell monolayer fully covering on the scaffold surface. Furthermore, the P(LA-co-GA-co-MMD) scaffolds benefit to excellent cell infiltration after subcutaneous implantation. These results indicated that the P(LA-co-GA-co-MMD) nanofibrous scaffolds could be potential candidates for vascular tissue engineering.

Biodegradable PEI modified complex micelles as gene carriers with tunable gene transfection efficiency for ECs

In recent years, gene therapy has evoked an increasing interest in clinical treatments of coronary diseases because it is a potential strategy to realize rapid endothelialization of artificial vascular grafts. The balance of high transfection efficiency and low cytotoxicity of nonviral gene carriers is an important issue to be solved. In this study, we aim to establish a gene delivery system offering an elegant way to tune the transfection activity and cytotoxicity. Biodegradable complex micelles were prepared from polyethylenimine-b-poly(lactide-co-3(S)-methyl-morpholine-2,5-dione)-b-polyethylenimine (PEI-b-PLMD-b-PEI) and methoxy-poly(ethylene glycol)-b-poly(lactide-co-3(S)-methyl-morpholine-2,5-dione) (mPEG-b-PLMD) copolymers by a co-assembly method. Then the ZNF580 gene plasmid (pDNA) was encapsulated into the complex micelles. The hydrodynamic size and zeta potential of these complex micelles and micelles/pDNA complexes indicated that they were feasible for use in cellular uptake and gene transfection. As expected, the transfection efficiency and cytotoxicity of these micelles/pDNA complexes could be conveniently tuned by changing the mass ratio of mPEG-b-PLMD to PEI-b-PLMD-b-PEI (3/1, 2/2, 1/3 and 0/4) in the mixed mPEG/PEI shell. The transfection efficiency increased as the mass ratio of mPEG-b-PLMD/PEI-b-PLMD-b-PEI decreased from 3/1 to 0/4, while the cytotoxicity showed an opposite tendency. Moreover, ZNF580 protein expression determined by Western blot analysis and the migration of transfected endothelial cells (ECs) by wound healing assay were consistent with the result of transfection efficiency. All these results indicated that the co-assembled complex micelles could act as suitable gene carriers with tunable gene transfection efficiency and cytotoxicity, which should have great potential for the transfection of vascular ECs.

Polydioxanone-based bio-materials for tissue engineering and drug/gene delivery applications

Since the commercialization of polydioxanone (PDX) as a biodegradable monofilament suture by Ethicon in 1981, the polymer has received only limited interest until recently. The limitations of polylactide-co-glycolide (PLGA) coupled with the growing need for materials with enhanced features and the advent of new fabrication techniques such as electrospinning have revived interest for PDX in medical devices, tissue engineering and drug delivery applications. Electrospun PDX mats show comparable mechanical properties as the major structural components of native vascular extracellular matrix (ECM) i.e. collagen and elastin. In addition, PDX's unique shape memory property provides rebound and kink resistance when fabricated into vascular conduits. The synthesis of methyl dioxanone (MeDX) monomer and copolymers of dioxanone (DX) and MeDX have opened up new perspectives for poly(ester-ether)s, enabling the design of the next generation of tissue engineering scaffolds for application in regenerating such tissues as arteries, peripheral nerve and bone. Tailoring of polymer properties and their formulation as nanoparticles, nanomicelles or nanofibers have brought along important developments in the area of controlled drug or gene delivery. This paper reviews the synthesis of PDX and its copolymers and provides for the first time an exhaustive account of its applications in the (bio)medical field with focus on tissue engineering and drug/gene delivery.

Nanoparticles complexed with gene vectors to promote proliferation of human vascular endothelial cells

Amphiphilic block copolymers containing biodegradable hydrophobic segments of depsipeptide based copolymers have been synthesized and explored as gene carriers for enhancing proliferation of endothelial cells in vitro. These polymers form nanoparticles (NPs) with positive charges on their surface, which could condense recombinant plasmids of enhanced green fluorescent protein plasmid and ZNF580 gene (pEGFP-ZNF580) and protect them against DNase I. ZNF580 gene is efficiently transported into EA.hy926 cells to promote their proliferation, whereby the transfection efficiency of NPs/pEGFP-ZNF580 is approximately similar to that of Lipofectamine 2000. These results indicate that the NPs might have potential as a carrier for pEGFP-ZNF580, which could support endothelialization of cardiovascular implants.

Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications

This review highlights the recent developments of surface modification and endothelialization of biomaterials in vascular tissue engineering applications.