Long-term and oxidative-responsive alginate–deferoxamine conjugates with a low toxicity for iron overload

Iron Overload in Brain: Transport Mismatches, Microbleeding Events, and How Nanochelating Therapies May Counteract Their Effects

Iron overload in many brain regions is a common feature of aging and most neurodegenerative diseases. In this review, the causes, mechanisms, mathematical models, and possible therapies are summarized. Indeed, physiological and pathological conditions can be investigated using compartmental models mimicking iron trafficking across the blood-brain barrier and the Cerebrospinal Fluid-Brain exchange membranes located in the choroid plexus. In silico models can investigate the alteration of iron homeostasis and simulate iron concentration in the brain environment, as well as the effects of intracerebral iron chelation, determining potential doses and timing to recover the physiological state. Novel formulations of non-toxic nanovectors with chelating capacity are already tested in organotypic brain models and could be available to move from in silico to in vivo experiments.

Developing Iron Nanochelating Agents: Preliminary Investigation of Effectiveness and Safety for Central Nervous System Applications

Excessive iron levels are believed to contribute to the development of neurodegenerative disorders by promoting oxidative stress and harmful protein clustering. Novel chelation treatments that can effectively remove excess iron while minimizing negative effects on the nervous system are being explored. This study focuses on the creation and evaluation of innovative nanobubble (NB) formulations, shelled with various polymers such as glycol-chitosan (GC) and glycol-chitosan conjugated with deferoxamine (DFO), to enhance their ability to bind iron. Various methods were used to evaluate their physical and chemical properties, chelation capacity in diverse iron solutions and impact on reactive oxygen species (ROS). Notably, the GC-DFO NBs demonstrated the ability to decrease amyloid-β protein misfolding caused by iron. To assess potential toxicity, in vitro cytotoxicity testing was conducted using organotypic brain cultures from the substantia nigra, revealing no adverse effects at appropriate concentrations. Additionally, the impact of NBs on spontaneous electrical signaling in hippocampal neurons was examined. Our findings suggest a novel nanochelation approach utilizing DFO-conjugated NBs for the removal of excess iron in cerebral regions, potentially preventing neurotoxic effects.

Development of cultivable alginate fibers for an ideal cell-cultivated meat scaffold and production of hybrid cultured meat

Slaughtering animals for meat pose several challenges, including environmental pollution and ethical concerns. Scaffold-based cell-cultivated meat has been proposed as a solution to these problems, however, the utilization of animal-derived materials for scaffolding or the high cost of production remains a significant challenge. Alginate is an ideal material for cell-cultivated meat scaffolds but has poor cell adhesion properties. To address this issue, we achieved 82 % cell adhesion coverage by controlling the specific structure generated during the ionic crosslinking process of alginate. Post 11 days of culture; we evaluated cell adhesion, differentiation, and aligned cell networks. The cell growth increased by 12.7 % compared to the initial seeding concentration. Finally, we created hybrid cell-cultivated meat by combining single-cell protein from mycelium and cell-cultivated meat. This is non-animal based, edible, cost-effective, and has a desirable texture by blending cell-cultivated meat with a meat analogue. In summary, the creation of improved alginate fibers can effectively tackle various obstacles encountered in the manufacturing of cell-cultivated meat. This includes enhancing cell adhesion, reducing costs, and streamlining the production procedure.

Fabrication of triple-crosslinked gelatin/alginate hydrogels for controlled release applications

Hydrogels have been demonstrated as smart drug carriers to recognize the tumor microenvironment for cancer treatment, where the dynamic crosslinks in the hydrogel network contribute to the stimuli-responsive features but also result in poor stability and weak mechanical property of the hydrogels. Here, phenylboronic acid-grafted polyethyleneimine (PBA-PEI)-modified gelatin (PPG) was synthesized to crosslink alginate dialdehyde (ADA) through imine bonds and boronate ester bonds, and then calcium ions (Ca2+) were added to introduce the third calcium-carboxylate crosslinking in the network to form the triple-crosslinked PPG/ADA-Ca2+ hydrogels. Given the three types of dynamic bonds in the network, PPG/ADA-Ca2+ hydrogels possessed a self-healing manner, stimuli-responsiveness, and better mechanical properties compared to single- or double-crosslinked hydrogels. The controlled release capability of PPG/ADA-Ca2+ hydrogels was also demonstrated, showing the encapsulated molecules can be rapidly released from the hydrogel network in the presence of hydrogen peroxide while the release rate can be slowed down at acidic pH. Furthermore, PPG/ADA-Ca2+ hydrogels presented selected cytotoxicity and drug delivery to cancer cells due to the regulated degradation by the cellular microenvironment. Taken together, PPG/ADA-Ca2+ hydrogels have been demonstrated as promising biomaterials with multiple desirable properties and dynamic features to perform controlled molecule release for biomedical applications.

Influence of Ionic Strength and Specific Ion Effects on Polyelectrolyte Multilayer Films with pH-Responsive Behavior

Layer-by-layer assembled multilayer films have shown great potential for different applications owing to their responsive behavior. Herein, we systematically investigated the effects of composition, salt concentration, and ion specificity on the pH responsiveness of covalently crosslinked chitosan and alginate dialdehyde multilayer films. The changes in film swelling were measured using ellipsometry from low (0.01 mM) to high (3 M) salt (NaCl or NaSCN) concentrations at pH 3, 6, and 9. The swelling responses to increasing ionic strength matched the swelling responses observed for polyzwitterionic and weak monocomponent polyelectrolyte films and depended on the multilayer composition, pH, and ion specificity. Finally, we used the ellipsometric data to demonstrate that the pH responsiveness of such multilayer films, as measured using a quartz crystal microbalance with dissipation monitoring, strongly depends on the ionic condition under which the responses were measured. We thus show that erroneous conclusions about the pH responsiveness of polyelectrolyte multilayer films can be easily obtained if the ionic environment of the application does not closely resemble the ionic condition under which the pH responsiveness is tested.

Dual Dynamic Covalently Crosslinked Alginate Hydrogels with Tunable Properties and Multiple Stimuli-Responsiveness

Alginate is a biopolymer that can be crosslinked with calcium ions to fabricate cytocompatible hydrogels. However, using calcium ions to crosslink alginate provides limited properties and functions to alginate hydrogels, restricting their biomedical applications. Here, phenylboronic acid-functionalized polyethyleneimine (PBA-PEI) was developed to introduce two orthogonal dynamic covalent crosslinks in the alginate hydrogels, where PBA-PEI was used to crosslink alginate dialdehyde (ADA) through imine bonds and boronate ester bonds. The grafting degree of PBA in the PEI structure was applied to fine-tune the properties of PBA-PEI/ADA hydrogels, including the rheological property, mechanical strength, swelling behavior, and antibacterial activity. In particular, the highly sensitive boronate ester bonds in the network enabled PBA-PEI/ADA hydrogels to be responsive to several stimuli, such as glucose, fructose, and hydrogen peroxide. Taken together, PBA-PEI/ADA hydrogels with tunable properties and multiple stimuli-responsiveness have been demonstrated as smart biomaterials for advanced biomedical applications.

Chelators for Treatment of Iron and Copper Overload: Shift from Low-Molecular-Weight Compounds to Polymers

Iron and copper are essential micronutrients needed for the proper function of every cell. However, in excessive amounts, these elements are toxic, as they may cause oxidative stress, resulting in damage to the liver and other organs. This may happen due to poisoning, as a side effect of thalassemia infusion therapy or due to hereditary diseases hemochromatosis or Wilson's disease. The current golden standard of therapy of iron and copper overload is the use of low-molecular-weight chelators of these elements. However, these agents suffer from severe side effects, are often expensive and possess unfavorable pharmacokinetics, thus limiting the usability of such therapy. The emerging concepts are polymer-supported iron- and copper-chelating therapeutics, either for parenteral or oral use, which shows vivid potential to keep the therapeutic efficacy of low-molecular-weight agents, while avoiding their drawbacks, especially their side effects. Critical evaluation of this new perspective polymer approach is the purpose of this review article.

Diethylenetriamine/NONOate-doped alginate hydrogel with sustained nitric oxide release and minimal toxicity to accelerate healing of MRSA-infected wounds

This study demonstrates the development of a nitric oxide (NO)-releasing hydrogel wound dressing and its efficacy at accelerating methicillin-resistant Staphylococcus aureus (MRSA)-infected wound healing. A DETA/NONOate-doped alginate (Alg-DETA/NO) hydrogel was synthesized using alginate as a hydrogel-forming wound dressing material and diethylenetriamine/diazeniumdiolate (DETA/NONOate) as an NO donor. Alg-DETA/NO exhibited a prolonged NO release profile over a period of 4 days. The rheological properties of Alg-DETA/NO did not differ significantly from those of pure alginate. Importantly, Alg-DETA/NO showed potent antibacterial activity against MRSA, with minimal toxicity to mouse fibroblasts. The application of Alg-DETA/NO to MRSA-infected wounds in a mouse model showed a favorable wound healing with accelerated wound-size reduction and reduced skin bacterial infection. Additionally, histological examination revealed that Alg-DETA/NO reduced inflammation at the wound site and promoted re-epithelialization, angiogenesis, and collagen deposition. Thus, Alg-DETA/NO presented herein could serve as a safe and potent hydrogel dressing for the treatment of MRSA-infected wounds.

Multifunctional injectable pluronic-cystamine-alginate-based hydrogel as a novel cellular delivery system towards tissue regeneration

This paper presents a new thermal sensitive hydrogel system based on cystamine-functionalised sodium alginate-g-pluronic F127 (ACP). The introduction of cystamine to the alginate backbone not only creates a covalent bond with pluronic F127 but also provides intrinsic anti-bacterial activity for the resultant hydrogel. The amount of water uptake inside the hydrogel remained ~200% for 6 days and the degradation was completed in 12 days in physiological media. The ACP copolymer solution could form a hydrogel at body temperature (~37 °C) and could return to the solution phase if the temperature decreased below 25o °C. Fibroblast encapsulated in situ in the ACP hydrogel maintained their viability (≥90% based on the live/dead assay) for 7 days, demonstrating the good biocompatibility of the ACP hydrogel for long-term cell cultivation. In addition, three-dimensional (3D) culture showed that fibroblast attached to the hydrogels and successfully mimicked the porous structure of the ACP hydrogel after 5 days of culture. Fibroblast cells could migrate from the cell-ACP clusters and form a confluent cell layer on the surface of the culture dish. Altogether, the obtained results indicate that the thermal-responsive ACP hydrogel synthesised in this study may serve as a cellular delivery platform for diverse tissue engineering applications.

Role of Iron in the Molecular Pathogenesis of Diseases and Therapeutic Opportunities

Iron is an essential mineral that serves as a prosthetic group for a variety of proteins involved in vital cellular processes. The iron economy within humans is highly conserved in that there is no proper iron excretion pathway. Therefore, iron homeostasis is highly evolved to coordinate iron acquisition, storage, transport, and recycling efficiently. A disturbance in this state can result in excess iron burden in which an ensuing iron-mediated generation of reactive oxygen species imparts widespread oxidative damage to proteins, lipids, and DNA. On the contrary, problems in iron deficiency either due to genetic or nutritional causes can lead to a number of iron deficiency disorders. Iron chelation strategies have been in the works since the early 1900s, and they still remain the most viable therapeutic approach to mitigate the toxic side effects of excess iron. Intense investigations on improving the efficacy of chelation strategies while being well tolerated and accepted by patients have been a particular focus for many researchers over the past 30 years. Moreover, recent advances in our understanding on the role of iron in the pathogenesis of different diseases (both in iron overload and iron deficiency conditions) motivate the need to develop new therapeutics. We summarized recent investigations into the role of iron in health and disease conditions, iron chelation, and iron delivery strategies. Information regarding small molecule as well as macromolecular approaches and how they are employed within different disease pathogenesis such as primary and secondary iron overload diseases, cancer, diabetes, neurodegenerative diseases, infections, and in iron deficiency is provided.

A bone regeneration strategy via dual delivery of demineralized bone matrix powder and hypoxia-pretreated bone marrow stromal cells using an injectable self-healing hydrogel

Demineralized bone matrix (DBM) powder is a potential alternative bone grafting material due to its bone regeneration capacity when the supply of autogenous bone is insufficient. However, the use of DBM powder alone remains challenging in many aspects in the clinic, such as its unstable osteoinductivity due to inactivation of growth factors during the preparation process, lack of bone regeneration cells, and difficulty in handling. Herein, we report a strategy that adopts a dual delivery of DBM powder and hypoxia-pretreated bone marrow stromal cells (BMSCs) using an injectable self-healing hydrogel to enhance bone regeneration and repair a cranial bone defect in a rabbit model. The injectable self-healing hydrogel was prepared based on a double crosslinking architecture, which comprised a dynamically cross-linked Schiff-base network as a self-healing component and a borax ion cross-linked physical network that strengthened its mechanical properties. The handling of the DBM powder was improved by mixing with the hydrogel, and, more importantly, the expression of osteocalcin (OCN) and vascular endothelial growth factor (VEGF) of the encapsulated BMSCs in the hydrogel was significantly up-regulated after hypoxia-pretreatment. The in vivo study demonstrated that the use of the hydrogel alone cannot heal the cranial bone defect, while the hydrogel/BMSC composite could increase the bone formation but was inferior to the hydrogel/DBM composite. Finally, the hydrogel/DBM/BMSC composite exhibited the best bone defect repairing effects among all groups. Overall, our results demonstrate that this dual delivery approach is a promising strategy to enhance bone regeneration for bone defect repair.

PEGylation of Deferoxamine for Improving the Stability, Cytotoxicity, and Iron-Overload in an Experimental Stroke Model in Rats

Deferoxamine (DFO) is a widely used drug for the treatment of iron-overload-related diseases in the clinic. However, its inherent shortcomings, such as a short plasma half-life and cytotoxicity, need to be addressed to widen its clinical utility. In this study, PEGylated DFO was first synthesized, and its chemical structure was characterized, and then in vitro and in vivo studies were performed. The metabolism assay showed that the stability of the PEGylated DFO was significantly improved, with a half-life 20 times greater than DFO. Furthermore, the PEGylated DFO exhibited significantly lower cytotoxicity compared with DFO. Additionally, the hemocompatibility assay showed that the PEGylated DFO had no significant effect on the coagulation system, red blood cells, complement, and platelets. In vivo studies indicated that PEGylated DFO was capable of reducing the iron accumulation, degeneration of neurons, and promotion of functional recovery. Taken together, PEGylated DFO improved stability, cytotoxicity, and iron-overload in an experimental stroke model in rats, making it a promising therapy for treating iron-overload conditions in the clinic.

Seaweed polysaccharide derived bioaldehyde nanocomposite: Potential application in anticancer therapeutics

In the present study, we have demonstrated synthesis of agar aldehyde (A_ald) from seaweed polysaccharide and its further successful application for preparation of A_ald mediated solid silver nanocomposite (A_ald-AgNPs). A_ald-AgNPs were characterized for biophysical properties by FTIR, XRD, SEM, TEM, XPS, and UV-vis spectroscopy. A_ald-AgNPs were further tested in vitro and in vivo for anticancer activity. The results of the in vitro study revealed that A_ald-AgNPs exhibited activity against 3 cancer cell lines. A_ald-AgNPs were found to act through causing dose dependent increase in cell size, inducing anueploidy, mitochondrial disintegration and increasing septa formation in cell cytoplasm. Results of in vivo anticancer activity against ME-180, Colon-26, and HL-60 xenograft mice tumor models showed 64 %, 27.3 % and 51 % reduction in tumor volume, respectively with 83-100 % survival rate. A_ald-AgNPs exhibited excellent antibacterial activity. It was interesting to note that A_ald-AgNPs did not exhibit any significant detrimental effect on viability and metabolic activity of normal bone marrow derived mesenchymal stem cells. This study opens new areas of research for chemists and biologists to use seaweed-derived polymers to develop nanocomposites for cancer therapeutics.

Nanocomposite bioink exploits dynamic covalent bonds between nanoparticles and polysaccharides for precision bioprinting

The field of bioprinting has made significant recent progress towards engineering tissues with increasing complexity and functionality. It remains challenging, however, to develop bioinks with optimal biocompatibility and good printing fidelity. Here, we demonstrate enhanced printability of a polymer-based bioink based on dynamic covalent linkages between nanoparticles (NPs) and polymers, which retains good biocompatibility. Amine-presenting silica NPs (ca. 45 nm) were added to a polymeric ink containing oxidized alginate (OxA). The formation of reversible imine bonds between amines on the NPs and aldehydes of OxA lead to significantly improved rheological properties and high printing fidelity. In particular, the yield stress increased with increasing amounts of NPs (14.5 Pa without NPs, 79 Pa with 2 wt% NPs). In addition, the presence of dynamic covalent linkages in the gel provided improved mechanical stability over 7 d compared to ionically crosslinked gels. The nanocomposite ink retained high printability and mechanical strength, resulting in generation of centimeter-scale porous constructs and an ear structure with overhangs and high structural fidelity. Furthermore, the nanocomposite ink supported both in vitro and in vivo maturation of bioprinted gels containing chondrocytes. This approach based on simple oxidation can be applied to any polysaccharide, thus the widely applicability of the method is expected to advance the field towards the goal of precision bioprinting.

Interactions of Alginate-Deferoxamine Conjugates With Blood Components and Their Antioxidation in the Hemoglobin Oxidation Model

While deferoxamine (DFO) has long been used as an FDA-approved iron chelator, its proangiogenesis ability attracts increasing number of research interests. To address its drawbacks such as short plasma half-life and toxicity, polymeric conjugated strategy has been proposed and shown superiority. Owing to intravenous injection and application in blood-related conditions, however, the blood interactions and antioxidation of the DFO-conjugates and the mechanisms underlying these outcomes remain to be elucidated. In this regard, incubating with three different molecular-weight (MW) alginate-DFO conjugates (ADs) red blood cells (RBCs), coagulation system, complement and platelet were investigated. To prove the antioxidant activity of ADs, we used hemoglobin oxidation model in vitro. ADs did not cause RBCs hemolysis while reversible aggregation and normal deformability ability were observed. However, the coagulation time, particularly APTT and TT, were significantly prolonged in a dose-dependent manner, and fibrinogen was dramatically decreased, suggesting ADs could dominantly inhibit the intrinsic pathways in the process of coagulation. The dose-dependent anticoagulation might be related with the functional groups along the alginate chains. The complements, C3a and C5a, were activated by ADs in a dose-dependent manner through alternative pathway. For platelet, ADs slightly suppressed the activation and aggregation at low concentration. Based on above results, the cross-talking among coagulation, complement and platelet induced by ADs was proposed. The antioxidation of ADs through iron chelation was proved and the antioxidant activity was shown in a MW-dependent manner.

Biocompatible disulphide cross-linked sodium alginate derivative nanoparticles for oral colon-targeted drug delivery

The application of layer-by-layer (LbL) approach on nanoparticle surface coating improves the colon-specific drug delivery of insoluble drugs. Here, we aimed to formulate a self-assembled cysteamine-based disulphide cross-linked sodium alginate with LbL self-assembly to improve the delivery of paclitaxel (PCX) to colonic cancer cells. Cysteamine was conjugated to the backbone of oxidized SA to form a core of self-assembled disulphide cross-linked nanospheres. P3DL was selected for PCX loading and fabricated LbL with poly(allylamine hydrochloride) (PAH) and poly(4-styrenesulfonic acid-co-maleic acid) sodium salt (PSSCMA) resulting from characterization and drug release studies. P3DL-fabricated PCX-loaded nanospheres (P3DL/PAH/PSSCMA) exhibited an encapsulation efficiency of 77.1% with cumulative drug release of 45.1%. Dynamic light scattering analysis was reported at 173.6 ± 2.5 nm with polydispersity index of 0.394 ± 0.105 (zeta potential= -58.5 mV). P3DL/PAH/PSSCMA demonstrated a pH-dependent swelling transition; from pH 1 to 7 (102.2% increase). The size increased by 33.0% in reduction response study after incubating with 10 mM glutathione (day 7). HT-29 cells showed high viabilities (86.7%) after treatment with the fabricated nanospheres at 0.8 µg/mL. Cellular internalization was successful with more than 70.0% nanospheres detected in HT-29 cells. Therefore, this fabricated nanospheres may be considered as potential nanocarriers for colon cancer-targeted chemotherapeutic drug delivery.

Structural Investigation of a Self-Cross-Linked Chitosan/Alginate Dialdehyde Multilayered Film with in Situ QCM-D and Spectroscopic Ellipsometry

A chitosan/alginate dialdehyde multilayered film was fabricated using the layer-by-layer assembly method. Besides electrostatic interaction that promotes alternate adsorption of the oppositely charged polyelectrolytes, the Schiff base reaction between the amine groups on chitosan and the aldehyde groups on alginate dialdehyde provides a covalently cross-linked film, which after reduction by sodium cyanoborohydride is stable under both acidic and alkaline conditions. Moreover, the cross-linked film is responsive to changes in pH and addition of multivalent salts. The structural properties of the multilayered film such as thickness, refractive index, and water content were examined using simultaneous quartz crystal microbalance with dissipation monitoring and spectroscopic ellipsometry.

Fabrication of alginate-based stimuli-responsive, non-cytotoxic, terpolymric semi-IPN hydrogel as a carrier for controlled release of bovine albumin serum and 5-amino salicylic acid

Herein, we report a functionalized alginate(Alg)-based terpolymeric semi-interpenetrating (semi-IPN) hydrogel, synthesized via free radical polymerization for the delivery of bovine albumin serum (BSA) and 5-amino salicylic acid (5-ASA). To improve mechanical properties, and to modulate surface morphology of Alg, 2-hydroxyethyl acrylate (HEA) was grafted on alginate and then crosslinked using poly(ethylene glycol) diacrylate (PEGDA). The probable structure and compositions of the synthesized semi-IPN terpolymer were identified by FTIR, ¹H-HR-MAS NMR, and TGA analyses. Achievement of equilibrium swelling state (ESS) and higher elastic modulus values confirmed terpolymer gel formation in aqueous media. Differences in the ESS of the prepared gel at pH 2.5 and 7.4 signify its stimuli-responsive behaviour. The influence of PEGDA on swelling, mechanical properties, surface morphology, cell viability and proliferation, and BSA and 5-ASA delivery were characterized. SEM images show that higher % PEGDA resulted in smaller sized pores in the gel network. Texture analyses demonstrate that hardness, adhesiveness and chewiness of the gel were enhanced at higher PEGDA concentrations. Increases in PEGDA concentration also induced increases in osteoblastic cell viability and higher rates of cell proliferation compared with gels containing lower concentrations of PEGDA. The release results indicate that the gels containing higher concentrations of PEGDA more sustainably release BSA and 5-ASA at 5 days and 30 h, respectively. The experimental data revealed that the synthesized terpolymeric semi-IPN hydrogel may have useful biomedical applications, especially as a carrier of protein (BSA), or 5-ASA (a therapeutic option for conditions of the colon such as Crohn's Disease and Ulcerative Colitis).