Biocompatible Alternatives Research Articles

Evaluation and Implementation of Biocompatible Methods for the Cross-linking of Plasma Proteins

Abstract Autologous plasma proteins can be used to fabricate patient specific cardiovascular implants but need to be cross-linked to increase their mechanical strength and reduce water solubility. Glutaraldehyde is the state-of-the-art solution but its reaction products have been shown to be cytotoxic and pro-inflammatory. In this work, it has been shown, that cross-linking of plasma proteins with biocompatible alternatives to glutaraldehyde is possible. This was achieved by identifying four candidate substances (thrombin, transglutaminase, genipin, EDC) from current literature and investigating their ability to cross-link porcine plasma proteins in vitro. The degree of crosslinking was examined using calorimetric (DSC) and spectroscopic (FTIR, Raman) methods, mapping the influence of cross-linking on the denaturation temperature and primary amino-group content of the proteins. It could be shown that thrombin, genipin and EDC are able to cross-link plasma proteins to a satisfactory degree and thus represent useful alternatives to glutaraldehyde. Transglutaminase, on the other hand, could not sufficiently cross-link the plasma proteins and was therefore ruled out as an alternative.

Effectiveness of Different Cellulose-Based Filtration Materials against Inhalation of SARS-CoV-2-Like Particles

The respiratory protection equipment (RPE) used by health professionals consists of an essential device to prevent infectious diseases, especially those caused by biological agents such as the coronavirus (SARS-CoV-2). The current epidemiological panorama is worrying, and the context of creation and production of the mask has emerged as an alternative to RPE to face the public health crisis worldwide. The aim of this work is to present a low-cost alternative as an FFP2-like filter for a reusable respirator face mask. This study presents the comparison of different cellulose-based filtering materials performed by retention testing, time saturation testing, aerosol penetration testing, nanoparticle (~140 nm) filtration testing, bacterial filtration efficiency (BFE), analysis of material morphology and usability. The reusable respirator face mask used in this study is an open-source innovation, using 3D printing. Cotton disc proved to be the best filter material for the reusable mask, with satisfactory results and a performance similar to that shown by the N95-type mask. The cotton disc ensured effectiveness over 6 h of use, and after that, the reusable respirator face mask (here, Delfi-TRON®) needed to be sanitized and replenished with a new cotton disc. Upon preliminary analyses of filtration efficiency, the selected filter was shown to be a low-cost biodegradable and biocompatible alternative.

Graphene Quantum Dots Co-Doped with Nitrogen/Mn(II) or Nitrogen/Gd(III) for Bimodal Magnetic Resonance and Fluorescence Imaging

Graphene quantum dots (GQDs) are unique derivatives of graphene that show promise in multiple biomedical applications as biosensors, bioimaging agents, and drug/gene delivery vehicles. Their ease in functionalization, biocompatibility, and intrinsic fluorescence enable those modalities. However, GQDs lack deep tissue magnetic resonance imaging (MRI) capabilities desirable for diagnostics. Considering that the drawbacks of MRI contrast agent toxicity are still poorly addressed, we develop novel Mn2+ or Gd3+ doped nitrogen-containing graphene quantum dots (NGQDs) to equip the GQDs with MRI capabilities and at the same time render contrast agents biocompatible. Water-soluble biocompatible Mn-NGQDs and Gd-NGQDs synthesized via single-step microwave-assisted scalable hydrothermal reaction enable dual MRI and fluorescence modalities. These quasi-spherical 3.9–6.6 nm average-sized structures possess highly crystalline graphitic lattice structure with 0.24 and 0.53 atomic % for Mn2+ and Gd3+ doping. This structure ensures high in vitro biocompatibility of up to 1.3 mg ml−1 and 1.5 mg ml−1 for Mn-NGQDs and Gd-NGQDs, respectively, and effective internalization in HEK-293 cells traced by intrinsic NGQD fluorescence. As MRI contrast agents with considerably low Gd and Mn content, Mn-NGQDs exhibit substantial transverse/longitudinal relaxivity (r 2/r 1) ratios of 11.190, showing potential as dual-mode longitudinal or transverse relaxation time (T 1 or T 2) contrast agents, while Gd-NGQDs possess r 2/r 1 of 1.148 with high r 1 of 9.546 mM−1 s−1 compared to commercial contrast agents, suggesting their potential as T1 contrast agents. Compared to other nanoplatforms, these novel Mn2+ and Gd3+ doped NGQDs not only provide scalable biocompatible alternatives as T1/T2 and T1 contrast agents but also enable in vitro intrinsic fluorescence imaging.

Synthesis and characterization of ZEin-based Low Density Porous Absorbent (ZELDA) for oil spill recovery

Removal of spilled petroleum oil from water bodies using hydrophobic porous absorbent has garnered considerable attention due to the simplicity, large-scale adaptability and robustness of the process. However, the use of nonbiodegradable synthetic oil absorbent during cleanup has raised a secondary concern such as generating plastic pollutants that can accumulate in marine and other ecosystems. To encounter this potential hazard, there is a need to find new biocompatible alternatives to currently used non-degradable porous materials. Here we present ZEin-based Low Density porous Absorbent (ZELDA) synthesized from an emulsion templating method as a new class of naturally derived porous material with tunable hydrophobicity for oil spill recovery. Corn-derived zein nanoparticles are first used to form oil-in-water Pickering emulsion. The addition of polymeric zein into the continuous aqueous phase of the emulsion, and its gradual phase separation enables the formation of a porous matrix. The pore diameter, surface wettability, and oil uptake capacity of ZELDA can be programmed by tuning oil-to-water phase volume ratio of the Pickering emulsion and its selective surface functionalization using flaxseed oil. The synthesis of ZELDA can be further modified with iron oxide nanoparticles to induce magnetic response, which enables its contactless maneuverability and removal from spilled site. The study outlines a new method of synthesis of zein-based porous materials and introduces synthetic routes for controlled surface functionalization, wettability, and stimuli responsiveness of the porous material. The synthesized plant-based material provides an ecofriendly alternative to commercially used nonbiodegradable oil sorbents for spilled oil remediation.

Oxime/Hydrazone Conjugation at Histidine: Late-Stage Functionalization Approach of Unprotected Peptides.

Synthetic molecular probes have recently been in focus for their potential use in target deconvolution, target engagement studies, and imaging. With the field expanding, new strategies to develop such tools are in high demand. While traditional conjugation techniques relying on inherently nucleophilic amino acids such as cysteine (Cys) and lysine (Lys) or pre-incorporated non-natural amino acids are still heavily used, novel methodologies for the direct and site-selective modification of peptides are attracting increasing attention. Of particular interest are Late-Stage Functionalization (LSF) approaches based on radical chemistry as they afford mild and biocompatible alternatives to transition-metal catalysis. A recent synthetic method, which leverages the unique reactivity of histidine (His), has proven to be a promising new strategy for LSF and site-selective conjugation of unprotected peptides. In this chapter, detailed step-by-step protocols depicting the C2-alkylation of His-containing peptides, the unveiling of a ketone as handle for hydrazone conjugation, and its use to site-selectively introduce a fluorophore at this residue are discussed. In addition to its application toward the synthesis of molecular probes, this methodology can be employed in peptide-based drug discovery programs, offering the possibility to rapidly explore the chemical space surrounding peptide hits. Finally, this strategy is also amenable to the preparation of novel peptide-ASO/small molecule drug conjugates.

Manganese–nitrogen and gadolinium–nitrogen Co-doped graphene quantum dots as bimodal magnetic resonance and fluorescence imaging nanoprobes

Graphene quantum dots (GQDs) are unique derivatives of graphene that show promise in multiple biomedical applications as biosensors, bioimaging agents, and drug/gene delivery vehicles. Their ease in functionalization, biocompatibility, and intrinsic fluorescence enable those modalities. However, GQDs lack deep tissue magnetic resonance imaging (MRI) capabilities desirable for diagnostics. Considering that the drawbacks of MRI contrast agent toxicity are still poorly addressed, we develop novel Mn2+ or Gd3+ doped nitrogen-containing graphene quantum dots (NGQDs) to equip the GQDs with MRI capabilities and at the same time render contrast agents biocompatible. Water-soluble biocompatible Mn-NGQDs and Gd-NGQDs synthesized via single-step microwave-assisted scalable hydrothermal reaction enable dual MRI and fluorescence modalities. These quasi-spherical 3.9–6.6 nm average-sized structures possess highly crystalline graphitic lattice structure with 0.24 and 0.53 atomic % for Mn2+ and Gd3+ doping. This structure ensures high in vitro biocompatibility of up to 1.3 mg ml−1 and 1.5 mg ml−1 for Mn-NGQDs and Gd-NGQDs, respectively, and effective internalization in HEK-293 cells traced by intrinsic NGQD fluorescence. As MRI contrast agents with considerably low Gd and Mn content, Mn-NGQDs exhibit substantial transverse/longitudinal relaxivity (r 2/r 1) ratios of 11.190, showing potential as dual-mode longitudinal or transverse relaxation time (T 1 or T 2) contrast agents, while Gd-NGQDs possess r 2/r 1 of 1.148 with high r 1 of 9.546 mM−1 s−1 compared to commercial contrast agents, suggesting their potential as T1 contrast agents. Compared to other nanoplatforms, these novel Mn2+ and Gd3+ doped NGQDs not only provide scalable biocompatible alternatives as T1/T2 and T1 contrast agents but also enable in vitro intrinsic fluorescence imaging.

Potential antibiofilm activity of farnesol-loaded poly(DL-lactide-co-glycolide) (PLGA) nanoparticles against Candida albicans

Candida species are ubiquitous fungal pathogens and are the most common causes of mucosal and invasive fungal infections in humans. Especially Candida albicans commonly resides as a commensal in the mucosal tissues of approximately half of the human population. When the balance of the normal flora is disrupted or the immune defenses are compromised, Candida species can become pathogenic, often causing recurrent disease in susceptible individuals.The treatments available for Candida infection are commonly drug-based and can involve topical and systemic antifungal agents. However, the use of standard antifungal therapies can be limited because of toxicity, low efficacy rates, and drug resistance. Candida species ability to produce drug-resistant biofilm is an important factor in human infections, because microorganisms within biofilm benefit from various advantages over their planktonic counterparts including protection from antimicrobials and chemicals. These limitations emphasize the need to develop new and more effective antifungal agents. Natural products are attractive alternatives for this purpose due to their broad spectrum of biological activities. Farnesol is produced by many microorganisms and found in some essential oils. It has also a great attention as a quorum-sensing molecule and virulence factor. It has also antimicrobial potential due to its inhibitory effects on various bacteria and fungi. However, as it is a hydrophobic component, its solubility and biofilm inhibiting properties are limited.To overcome these shortcomings, nanoparticle-based drug delivery systems have been successfully used. For this purpose, especially using biodegradable polymeric nanoparticles has gained increasing attention owing to their biocompatibility and minimal toxicity. Poly (DL-lactide-co-glycolide) (PLGA) is the most widely used polymer in this area. In this study, farnesol is loaded to PLGA nanoparticles (F-PLGA NPs) by emulsion evaporation method and characterized by DLS, TEM, and FT-IR analyses. Our TEM findings indicate that the sizes of F-PLGA NPs are approximately 140 nm. The effects of F-PLGA NPs on planktonic cells and biofilm formation of C. albicans were compared with effects of farnesol alone. Farnesol inhibits the growth at a range of 53% at a concentration of 2.5 μL compared to the control group. This rate is 45% for F-PLGA NPs at the same concentration. However, although farnesol amount in F-PLGA is approximately 22.5% of the total volume, the observed effect is significant. In TEM examinations, planktonic Candida cells treated with farnesol showed relatively regular ultrastructural morphology. Few membrane and wall damage and electron density in the cytoplasm were determined. In F-PLGA NP-treated cells, increased irregular cell morphology, membrane and wall damages, and large vacuoles are observed. Our SEM and XTT data suggest that F-PLGA NPs can reduce the biofilm formation at lower concentrations than farnesol alone 57%, and our results showed that F-PLGA NPs are effective and biocompatible alternatives for inhibiting growth and biofilm formation of C. albicans, but detailed studies are needed.

The Elusive Nature of Carbon Nanodot Fluorescence: An Unconventional Perspective

The burgeoning interest raised by carbon dots (CDs) is an epitome of the urgency to develop green and biocompatible alternatives to inorganic and hybrid quantum dots. The fast-paced development of synthetic approaches for CDs over the past few years has left many open questions on their characterization. Herein, we further confirm how the standardization of CDs cannot disregard the presence of fluorescent molecular byproducts. On the contrary, we show how the emissive properties of our solvothermally synthesized CDs largely stem from free molecular adducts produced during the synthesis of carbon cores. The presence of these small molecules, not detectable by electron microscopy, could be deceptive for a reliable characterization of the CDs and could lead to an overestimate of their optical properties. Hence, we propose to introduce more bias-free structure–property correlations based on spectroscopy techniques capable of giving direct insights into their structural properties. Through a combination of standard and unconventional characterization techniques, such as fluorescence correlation spectroscopy (FCS) and time-resolved electron paramagnetic resonance (TREPR), we demonstrate how molecular byproducts dominate the emission properties: these are freely moving in the solution rather than decorating a carbonaceous scaffold. Considering carefully the possibility that newly synthesized CDs are heterogeneous solutions will boost the research and optimization of CDs, thereby paving the way to the large-scale production of cheap and biocompatible light-emissive nanostructures.

Recent Developments and Practical Feasibility of Polymer‐Based Antifouling Coatings

AbstractWhile nature has optimized its antifouling strategies over millions of years, synthetic antifouling coatings have not yet reached technological maturity. For an antifouling coating to become technically feasible, it should fulfill many requirements: high effectiveness, long‐term stability, durability, ecofriendliness, large‐scale applicability, and more. It is therefore not surprising that the search for the perfect antifouling coating has been going on for decades. With the discovery of metal‐based antifouling paints in the 1970s, fouling was thought to be a problem of the past, yet its untargeted toxicity led to serious ecological concern, and its use became prohibited. As a response, research shifted focus toward a biocompatible alternative: polymer‐based antifouling coatings. This has resulted in numerous advanced and innovative antifouling strategies, including fouling‐resistant, fouling‐release, and fouling‐degrading coatings. Here, these novel and exciting discoveries are highlighted while simultaneously assessing their antifouling performance and practical feasibility.

Unprecedented Kinetic Inertness for a Mn2+ -Bispidine Chelate: A Novel Structural Entry for Mn2+ -Based Imaging Agents.

The search for more biocompatible alternatives to Gd3+ -based MRI agents, and the interest in 52 Mn for PET imaging call for ligands that form inert Mn2+ chelates. Given the labile nature of Mn2+ , high inertness is challenging to achieve. The strongly preorganized structure of the 2,4-pyridyl-disubstituted bispidol ligand L1 endows its Mn2+ complex with exceptional kinetic inertness. Indeed, MnL1 did not show any dissociation for 140 days in the presence of 50 equiv. of Zn2+ (37 °C, pH 6), while recently reported potential MRI agents MnPyC3A and MnPC2A-EA have dissociation half-lives of 0.285 h and 54.4 h under similar conditions. In addition, the relaxivity of MnL1 (4.28 mm-1 s-1 at 25 °C, 20 MHz) is remarkable for a monohydrated, small Mn2+ chelate. In vivo MRI experiments in mice and determination of the tissue Mn content evidence rapid renal clearance of MnL1 . Additionally, L1 could be radiolabeled with 52 Mn and the complex revealed good stability in biological media.

Unprecedented Kinetic Inertness for a Mn2+‐Bispidine Chelate: A Novel Structural Entry for Mn2+‐Based Imaging Agents

AbstractThe search for more biocompatible alternatives to Gd3+‐based MRI agents, and the interest in 52Mn for PET imaging call for ligands that form inert Mn2+ chelates. Given the labile nature of Mn2+, high inertness is challenging to achieve. The strongly preorganized structure of the 2,4‐pyridyl‐disubstituted bispidol ligand L1 endows its Mn2+ complex with exceptional kinetic inertness. Indeed, MnL1 did not show any dissociation for 140 days in the presence of 50 equiv. of Zn2+ (37 °C, pH 6), while recently reported potential MRI agents MnPyC3A and MnPC2A‐EA have dissociation half‐lives of 0.285 h and 54.4 h under similar conditions. In addition, the relaxivity of MnL1 (4.28 mm−1 s−1 at 25 °C, 20 MHz) is remarkable for a monohydrated, small Mn2+ chelate. In vivo MRI experiments in mice and determination of the tissue Mn content evidence rapid renal clearance of MnL1. Additionally, L1 could be radiolabeled with 52Mn and the complex revealed good stability in biological media.

Abstract B116: Nano-neo-mRNA vaccine: A novel platform technology for cancer-immunotherapy

Abstract Nanoparticle-based immunotherapeutic platforms are emerging as radically different, biocompatible alternatives for viral-vectors. Liposomal nanoplexes already showed potential for clinical translation of mutanome specific personalized cancer-vaccines in human. Here, we report a novel nanoparticle platform technology for neoantigen specific mRNA (neo-mRNA) vaccine delivery and demonstrated its potential for evoking T-cell mediated immune response against drug/radiation resistant glioma cells. Glioblastoma multiforme (GBM) is one of the most aggressive type primary brain tumors with high rate of recurrence and poor prognosis. Temozolomide (TMZ) chemotherapy in concurrence with radiation is less effective for patients with over-expression of DNA repair protein, O6-methyl guanine-DNA methyltransferase (MGMT) or epidermal growth factor receptor variant III (EGFRvIII) mutation. Here, we developed a unique pathogen mimicking nanoparticle platform that can effectively encapsulate and transfect dendritic cells with mRNA vaccine specific to MGMT or EGFRvIII. MGMT/EGFRvIII mRNA was synthesized by in vitro transcription (IVT) from respective cDNA plasmid and 100-150nm sized nanoplex was formed with mRNA at the core with >90% encapsulation efficiency. This Nano-neo-mRNA vaccineTM platform was successfully delivered to human monocyte derived DCs with a transfection efficiency of 35-50% compared to 3-5% in the case of naked mRNA. The transfected DCs showed significant phenotypic expression of MGMT-GFP with MHC I/II and CD80/86 co-activation compared to the naked mRNA or vehicle control. The efficiency of vaccinated DCs to prime cytotoxic T-cells was demonstrated in co-cultures where the nanoplex showed efficient activation of T-cell-mediated cytotoxicity on MGMT or EGFRvIII expressing, TMZ/radiation resistant glioblastoma cells . Biocompatibility of the nano-carrier was demonstrated in primary human cells and animal models. Thus, we present a new, biocompatible nanoparticle platform technology for IVT-mRNA based cancer-immunotherapy. Citation Format: Manzoor Koyakutty, Navyashree A. Ramesh, Ashwathy Nambiar, Najuma Nujum Ambili Anna, Manju C. Abraham, Minu Anoop, Anjana Ramkumar, Nair Shanti, Vijay Harish Harish, Anusha Ashokan. Nano-neo-mRNA vaccine: A novel platform technology for cancer-immunotherapy [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B116.

Poly(Alkyl Glycidate Carbonate)s as Degradable Pressure‐Sensitive Adhesives

AbstractInsertion of CO2 into the polyacrylate backbone, forming poly(carbonate) analogues, provides an environmentally friendly and biocompatible alternative. The synthesis of five poly(carbonate) analogues of poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate) is described. The polymers are prepared using the salen cobalt(III) complex catalyzed copolymerization of CO2 and a derivatized oxirane. All the carbonate analogues possess higher glass‐transition temperatures (Tg=32 to −5 °C) than alkyl acrylates (Tg=10 to −50 °C), however, the carbonate analogues (Td≈230 °C) undergo thermal decomposition at lower temperatures than their acrylate counterparts (Td≈380 °C). The poly(alkyl carbonates) exhibit compositional‐dependent adhesivity. The poly(carbonate) analogues degrade into glycerol, alcohol, and CO2 in a time‐ and pH‐dependent manner with the rate of degradation accelerated at higher pH conditions, in contrast to poly(acrylate)s.

Quantum confined peptide assemblies with tunable visible to near-infrared spectral range

Quantum confined materials have been extensively studied for photoluminescent applications. Due to intrinsic limitations of low biocompatibility and challenging modulation, the utilization of conventional inorganic quantum confined photoluminescent materials in bio-imaging and bio-machine interface faces critical restrictions. Here, we present aromatic cyclo-dipeptides that dimerize into quantum dots, which serve as building blocks to further self-assemble into quantum confined supramolecular structures with diverse morphologies and photoluminescence properties. Especially, the emission can be tuned from the visible region to the near-infrared region (420 nm to 820 nm) by modulating the self-assembly process. Moreover, no obvious cytotoxic effect is observed for these nanostructures, and their utilization for in vivo imaging and as phosphors for light-emitting diodes is demonstrated. The data reveal that the morphologies and optical properties of the aromatic cyclo-dipeptide self-assemblies can be tuned, making them potential candidates for supramolecular quantum confined materials providing biocompatible alternatives for broad biomedical and opto-electric applications.

Molecular Dynamics Simulations on Nucleic Acid Binding Polymers Designed To Arrest Thrombosis.

Cancer-associated thrombosis is managed by the administration of anticoagulants and antithrombotic agents that have a high risk of inducing hemorrhagic complications. To develop safer strategies for antithrombotic therapy, in vivo activators of the intrinsic pathway, namely, cell-free nucleic acids (DNA and RNA) have been targeted with cationic, polyamine-based polymers. The cytotoxicity of the highly cationic polymers is a major drawback for their practical use, and biocompatible alternatives are in high demand. In this study, we carried out all-atom molecular dynamics simulations to systematically examine the DNA binding of polyamine-poly(ethylene glycol) (PEG) diblock polymers designed from biocompatible building blocks to inhibit the procoagulant activity of DNA. The differences in cationic charge, PEG chain length, and initial conformations of the polymers resulted in marked differences in their binding to DNA. We found that having an exposed cationic polyamine group is essential to polymer-DNA binding and a certain level of electrostatic interactions is necessary to maintain the bound state. Intrachain associations between the polyamine groups and PEG chains in some cases have led to a collapsed state of the polymer that precludes binding to DNA. This self-association is mainly due to a strong hydrogen bond between polymer polyamine and PEG groups and partly due to a partially charged semibranched polyamine group architecture. As polymer "masking" of DNA is thought to arrest DNA's prothrombotic activity, our findings highlight the desired structural features of the polymers for stronger DNA binding and provide insights into the design of novel antithrombotic agents.

The synthesis and characterization of a magnetite nanoparticle with potent antibacterial activity and low mammalian toxicity

Magnetite has shown some promise as a biomedical material and antibacterial agent; however the benefits are normally only realized when it is used in combination with other metals or drugs. Unfunctionalized magnetite may be a biocompatible alternative. This report discusses the synthesis and potent antibacterial activity, with low associated mammalian organ toxicity, of nanomagnetite particles. Magnetite (Fe3O4) nanoparticles were electrochemically prepared in a green surfactant-free, closed water loop system. These materials, characterized by X-ray diffraction, FTIR, and vibrational magnetometry, also appear contaminated with Fe-O-O-H functionalities. This physical characterization is accompanied by a computational investigation of truncated clusters showing that a magnetite-derived cluster of 7 iron atoms is a sufficient model to generate the vibrational frequencies experimentally observed in magnetite using DFT calculations. The nanoparticles, evaluated for antibiotic activity, were shown to have minimum inhibitory concentrations of 2.8 and 2.0 μg/mL against E. coli and S. aureus respectively. This is both a 100-fold lower concentration than the human cytotoxic dose determined by an MTT assay and is also comparable to the effective dose of traditional antibiotics. A dose-dependent decrease in catalase activity and an increase in the levels of lipid peroxidation suggests that these nanoparticles act through damaging the anti-oxidant systems in cells. However, renal and hepatic damage was only observed at daily doses (2 weeks) of 100 μg/mL and higher. This significant therapeutic window suggests that these materials might prove useful as potential complementary therapeutics in the future.

Synthesis of ABA Tri-Block Co-Polymer Magnetopolymersomes via Electroporation for Potential Medical Application

The ABA tri-block copolymer poly(2-methyloxazoline)–poly(dimethylsiloxane)–poly(2-methyloxazoline) (PMOXA–PDMS–PMOXA) is known for its capacity to mimic a bilayer membrane in that it is able to form vesicular polymersome structures. For this reason, it is the subject of extensive research and enables the development of more robust, adaptable and biocompatible alternatives to natural liposomes for biomedical applications. However, the poor solubility of this polymer renders published methods for forming vesicles unreproducible, hindering research and development of these polymersomes. Here we present an adapted, simpler method for the production of PMOXA–PDMS–PMOXA polymersomes of a narrow polydispersity (45 ± 5.8 nm), via slow addition of aqueous solution to a new solvent/polymer mixture. We then magnetically functionalise these polymersomes to form magnetopolymersomes via in situ precipitation of iron-oxide magnetic nanoparticles (MNPs) within the PMOXA–PDMS–PMOXA polymersome core and membrane. This is achieved using electroporation to open pores within the membrane and to activate the formation of MNPs. The thick PMOXA–PDMS–PMOXA membrane is well known to be relatively non-permeable when compared to more commonly used di-block polymer membranes due a distinct difference in both size and chemistry and therefore very difficult to penetrate using standard biological methods. This paper presents for the first time the application of electroporation to an ABA tri-block polymersome membrane (PMOXA–PDMS–PMOXA) for intravesicular in situ precipitation of uniform MNPs (2.6 ± 0.5 nm). The electroporation process facilitates the transport of MNP reactants across the membrane yielding in situ precipitation of MNPs. Further to differences in length and chemistry, a tri-block polymersome membrane structure differs from a natural lipid or di-block polymer membrane and as such the application and effects of electroporation on this type of polymersome is entirely novel. A mechanism is hypothesised to explain the final structure and composition of these biomedically applicable tri-block magnetopolymersomes.

Hierarchical patterning of multifunctional conducting polymer nanoparticles as a bionic platform for topographic contact guidance.

The use of programmed electrical signals to influence biological events has been a widely accepted clinical methodology for neurostimulation. An optimal biocompatible platform for neural activation efficiently transfers electrical signals across the electrode-cell interface and also incorporates large-area neural guidance conduits. Inherently conducting polymers (ICPs) have emerged as frontrunners as soft biocompatible alternatives to traditionally used metal electrodes, which are highly invasive and elicit tissue damage over long-term implantation. However, fabrication techniques for the ICPs suffer a major bottleneck, which limits their usability and medical translation. Herein, we report that these limitations can be overcome using colloidal chemistry to fabricate multimodal conducting polymer nanoparticles. Furthermore, we demonstrate that these polymer nanoparticles can be precisely assembled into large-area linear conduits using surface chemistry. Finally, we validate that this platform can act as guidance conduits for neurostimulation, whereby the presence of electrical current induces remarkable dendritic axonal sprouting of cells.

Replacement of acetate with citrate in dialysis fluid: a randomized clinical trial of short term safety and fluid biocompatibility

BackgroundThe majority of bicarbonate based dialysis fluids are acidified with acetate. Citrate, a well known anticoagulant and antioxidant, has been suggested as a biocompatible alternative. The objective of this study was to evaluate short term safety and biocompatibility of a citrate containing acetate-free dialysis fluid.MethodsTwenty four (24) patients on maintenance dialysis three times per week, 13 on on-line hemodiafiltration (HDF) and 11 on hemodialysis (HD), were randomly assigned to start with either citrate dialysis fluid (1 mM citrate, 1.5 mM calcium) or control fluid (3 mM acetate, 1.5 mM calcium) in an open-labeled cross-over trial (6 + 6 weeks with 8 treatments wash-out in between). Twenty (20) patients, 11 on HDF and 9 on HD were included in the analyses. Main objective was short term safety assessed by acid–base status, plasma ionized calcium and parathyroid hormone (PTH). In addition, biocompatibility was assessed by markers of inflammation (pentraxin 3 (PTX-3), CRP, IL-6, TNF-α and IL-1β) and thrombogenicity (activated partial thromboplastin time (APTT) and visual clotting scores).ResultsNo differences dependent on randomization order or treatment mode (HD vs. HDF) were detected. Citrate in the dialysis fluid reduced the intra-dialytic shift in pH (+0.04 week 6 vs. +0.06 week 0, p = 0.046) and base excess (+3.9 mM week 6 vs. +5.6 mM week 0, p = 0.006) over the study period. Using the same calcium concentration (1.5 mM), citrate dialysis fluid resulted in lower post-dialysis plasma ionized calcium level (1.10 mM vs. 1.27 mM for control, p < 0.0001) and higher post-dialysis PTH level (28.8 pM vs. 14.7 pM for control, p < 0.0001) while pre-dialysis levels were unaffected. Citrate reduced intra-dialytic induction of PTX-3 (+1.1 ng/ml vs. +1.4 ng/ml for control, p = 0.04) but had no effect on other markers of inflammation or oxidative stress. Citrate reduced visual clotting in the arterial air chamber during HDF (1.0 vs. 1.8 for control, p = 0.03) and caused an intra-dialytic increase in APTT (+6.8 s, p = 0.003) without affecting post-dialysis values compared to control.ConclusionsDuring this small short term study citrate dialysis fluid was apparently safe to use in HD and on-line HDF treatments. Indications of reduced treatment-induced inflammation and thrombogenicity suggest citrate as a biocompatible alternative to acetate in dialysis fluid. However, the results need to be confirmed in long term studies.Trial registrationISRCTN: ISRCTN28536511

Biocompatibility of root canal filling materials.

Results of in vitro and in vivo studies clearly indicate that some endodontic sealers may cause local and systemic adverse effects. Though occasionally contradictory data has been reported from various authors, it may be concluded that zinc-oxide-eugenol sealers possess a marked cytotoxic and tissue-irritating potency. Most Ca(OH)2-based materials, however, were biocompatible. Genotoxic effects have been observed with sealers releasing paraformaldehyde or containing mutagenic substances, such as bisphenol-A-diglycidyl-ether or its derivatives. It cannot be excluded that these materials may pose a systemic risk because formaldehyde is rapidly distributed systemically following its application into the pulp cavity. Furthermore an increasing number of cases with an aspergillosis of the maxillary sinus have been observed which were mainly caused by zinc-releasing endodontic sealers. Overall, it is recommended that for endodontic practice, sealers that have been found to be biocompatible in a "mixed bag" of various in vitro and in vivo tests, be selected. From this point of view, ZnOE-sealers should no longer be used for root canal fillings. This recommendation applies also to sealers containing paraformaldehyde or generating this substance during their setting reaction. More experimental and clinical studies are necessary to elucidate whether new materials, such as mineral trioxide aggregate (MTA) or calcium phosphate cement, will be biocompatible alternatives in the future.