Heparin as a molecular spacer immobilized on microspheres to improve blood compatibility in hemoperfusion

Effectively adsorb Au(S2O3)23- using aminoguanidine as trapping group from thiosulfate solutions

Thiosulfate gold leaching is one of the most promising green cyanide-free gold extraction processes; however, the difficulty of recovering Au(I) from the leaching system hinders its further development. This study prepared aminoguanidine-functionalized microspheres (AGMs) via a one-step reaction involving nucleophilic substitution between aminoguanidine hydrochloride and chloromethylated polystyrene microspheres and used AGMs to adsorb Au(I) from thiosulfate solutions. Scanning electron microscopy, Brunauer-Emmett-Teller analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to analyze the structure and properties of AGMs. Experiments were designed to investigate the effects of pH, temperature, initial Au(I), and thiosulfate concentrations on the gold adsorption performance of AGMs. Results demonstrated that AGMs can efficiently adsorb Au(I) from thiosulfate solutions in a wide pH range. The adsorption process conforms to the pseudo-second-order kinetic model and Langmuir isotherm model, with a maximum capacity of 22.03 kg/t. Acidic thiourea is an effective desorbent, and after four adsorption-desorption cycles, the adsorption rate of Au(I) by AGMs is 78.63%, which shows AGMs have good cyclic application potential. Based on the results of characterization, experiments, and density functional theory calculations, the mechanism for the adsorption of [Au(S2O3)2]3- on AGMs involves anion exchange. Importantly, AGMs exhibited satisfactory adsorption property for Au(I) in practical Cu2+-NH3(en)-S2O32- systems. This study provided experimental reference for the recovery of Au(I) from thiosulfate solution.

Heparin-Mimetic Chitooligosaccharides-Based Monoliths Obtained from C/W Emulsions: Hemocompatibility and Toxin Removal Ability

Hemoperfusion (HP) is one of the most prominent therapies for treating uremia, hyperbilirubinemia, and acute drug toxicity. The comprehensive performance of currently used porous HP adsorbents needs to be improved due to the impediment to their synthesis strategy. Herein, green carbon dioxide-in-water high internal phase emulsions (C/W HIPEs) were utilized and emulsified with poly(vinyl alcohol) (PVA) for the formation of a heparin-mimetic chitosan oligosaccharides/poly(acrylamide-co-sodium 4-styrenesulfonate) [COS/P(AM-co-SSS)] monolith, which exhibited good mechanical properties, stable swelling performance, hydrophilic properties, anticoagulant effect, and low hemolysis. It showed a strong toxin adsorption capacity (415.2 mg/g for creatinine, 199.3 mg/g for urea, 279.5 mg/g for bilirubin, and 160 mg/g for tetracycline). The adsorption process of porous COS/P(AM-co-SSS) followed the pseudo-second-order kinetic and Langmuir isotherm models. Moreover, the porous materials had a strong electrostatic force on creatinine. The removal of creatinine by simulated in vitro blood perfusion was 80.2% within 30 min. This work provides a green preparation strategy for developing novel HP materials, highlighting their potential application value in blood and environmental purification.

Broad-Spectrum Clearance of Lipopolysaccharides from Blood Based on a Hemocompatible Dihistidine Polymer

Blood infection can release toxic bacterial lipopolysaccharides (LPSs) into bloodstream, trigger a series of inflammatory reactions, and eventually lead to multiple organ dysfunction, irreversible shock, and even death, which seriously threatens human life and health. Herein, a functional block copolymer with excellent hemocompatibility is proposed to enable broad-spectrum clearance of LPSs from whole blood blindly before pathogen identification, facilitating timely rescue from sepsis. A dipeptide ligand of histidine-histidine (HH) was designed as the LPS binding unit, and poly[(trimethylamine N-oxide)-co-(histidine-histidine)], a functional block copolymer combining the LPS ligand of HH and a zwitterionic antifouling unit of trimethylamine N-oxide (TMAO), was then designed by reversible addition-fragmentation chain transfer (RAFT) polymerization. The functional polymer achieved effective clearance of LPSs from solutions and whole blood in a broad-spectrum manner and had good antifouling and anti-interference properties and hemocompatibility. The proposed functional dihistidine polymer provides a novel strategy for achieving broad-spectrum clearance of LPSs, with potential applications in clinical blood purification.

Antibacterial intraosseous implant surface coating that responds to changes in the bacterial microenvironment

Bone implant-associated infection is one of the most challenging problems encountered by orthopedic surgeons. There is considerable interest in the development of drug-loaded antibacterial coatings for the surfaces of metal implants. However, it is difficult to achieve the stable local release of an effective drug dose for many antibacterial coatings. In the present study, analyses of the thickness and water contact angle of multiple layers confirmed the successful assembly of multilamellar membrane structures. Measurement of the zone of bacterial inhibition indicated gradual degradation of the (montmorillonite [MMT]/hyaluronic acid [HA])₁₀ multilamellar film structure with concentration-dependent degradation during incubation with hyaluronidase solution and Staphylococcus aureus. In vivo results resembled the in vitro results. Overall, the findings confirm that the (MMT/HA-rifampicin)₁₀ multilamellar film structure exhibits good antibacterial properties and excellent biocompatibility. Further studies of the clinical potential of the antibacterial coating prepared in this experiment are warranted.

Fabrication of 2D nanosheet sorbents through metastable emulsion droplets and subsequent two-step grafting polymerization for efficient blood lead removal in vitro

Hemoperfusion is a powerful and yet simple method for lead poisoning treatment, but creation of safe and effective sorbents with excellent selectivity remains a real challenge. To address this, we here construct 2D nanosheet sorbents (BM-SH) through metastable emulsion droplets and subsequent two-step grafting polymerization for efficient blood lead removal in vitro. Metastable emulsion droplets endow typical nanosized sheet-like structure (thickness of 30 nm) and relatively round shape. The consecutive two grafting processes using hydroxyethyl methacrylate (HEMA) and L-cysteine monomer (D-SH) provide BM-SH with a high density of accessible binding sites towards lead ions (Pb²⁺). A high adsorption capacity of 390.5 mg g^-1 and quick capture 97.35 % of Pb²⁺ within initial 10 min are obtained, surpassing most of the reported sorbents for lead removal. Besides, adsorption distribution coefficient (K_d) of BM-SH among four coexisting metal ions achieved 7792 mL g^-1, showing outstanding selectivity toward Pb²⁺. Importantly, a possible adsorption mechanism is recognized as coordination with carboxyl, sulfydryl and imino groups from L-cysteine, and mercapto ligand as the key chelating agent may be the reason for high Pb²⁺ affinity. And what's more, BM-SH displays good hemocompatibility and high efficiency of blood lead removal rate (above 86 % in vitro).

Polyethyleneimine-assisted co-deposition of polydopamine coating with enhanced stability and efficient secondary modification

The stability and grafting efficiency are important for polydopamine (pDA) coatings used as platforms for secondary grafting.

Emerging nanomaterials applied for tackling the COVID-19 cytokine storm

During the global outbreak of coronavirus disease 2019 (COVID-19), a hyperinflammatory state called the cytokine storm was recognized as a major contributor to multiple organ failure and mortality. However, to date, the diagnosis and treatment of the cytokine storm remain major challenges for the clinical prognosis of COVID-19. In this review, we outline various nanomaterial-based strategies for preventing the COVID-19 cytokine storm. We highlight the contribution of nanomaterials to directly inhibit cytokine release. We then discuss how nanomaterials can be used to deliver anti-inflammatory drugs to calm the cytokine storm. Nanomaterials also play crucial roles in diagnostics. Nanomaterial-based biosensors with improved sensitivity and specificity can be used to detect cytokines. In summary, emerging nanomaterials offer platforms and tools for the detection and treatment of the COVID-19 cytokine storm and future pandemic.

Surface modification of polytetrafluoroethylene (PTFE) with a heparin-immobilized extracellular matrix (ECM) coating for small-diameter vascular grafts applications

Intimal hyperplasia, thrombosis formation, and delayed endothelium regeneration are the main causes that restrict the clinical applications of PTFE small-diameter vascular grafts (inner diameter < 6 mm). An ideal strategy to solve such problems is to facilitate in situ endothelialization. Since the natural vascular endothelium adheres onto the basement membrane, which is a specialized form of extracellular matrix (ECM) secreted by endothelial cells (ECs) and smooth muscle cells (SMCs), functionalizing PTFE with an ECM coating was proposed. However, besides ECs, the ECM-modified PTFE improved SMC growth as well, thereby increasing the risk of intimal hyperplasia. In the present study, heparin was immobilized on the ECM coating at different densities (4.89 ± 1.02 μg/cm2, 7.24 ± 1.56 μg/cm2, 15.63 ± 2.45 μg/cm2, and 26.59 ± 3.48 μg/cm2), aiming to develop a bio-favorable environment that possessed excellent hemocompatibility and selectively inhibited SMC growth while promoting endothelialization. The results indicated that a low heparin density (4.89 ± 1.02 μg/cm2) was not enough to restrict platelet adhesion, whereas a high heparin density (26.59 ± 3.48 μg/cm2) resulted in decreased EC growth and enhanced SMC proliferation. Therefore, a heparin density at 7.24 ± 1.56 μg/cm2 was the optimal level in terms of antithrombogenicity, endothelialization, and SMC inhibition. Collectively, this study proposed a heparin-immobilized ECM coating to modify PTFE, offering a promising means to functionalize biomaterials for developing small-diameter vascular grafts.

Advances in the Development of Biomaterials for Endotoxin Adsorption in Sepsis

Sepsis, a life-threatening and intractable disease without any specific treatment, is activated by endotoxin. Some attempts at removing endotoxin to treat sepsis from the blood circulation using different hemoperfusion cartridges have been proposed recently, but they have failed to reduce the mortality of severe septic patients. This review summarizes the latest advances in the development of endotoxin adsorbents. In particular, we highlight two critical parameters for endotoxin adsorbents when they are applied in blood purification: the dissociation constant and the maximum adsorption capacity. We also discuss potential challenges and research directions for the future development of endotoxin adsorbents.

Ultraefficiently Calming Cytokine Storm Using Ti3C2T x MXene

During the global outbreak of COVID-19 pandemic, "cytokine storm" conditions are regarded as the fatal step resulting in most mortality. Hemoperfusion is widely used to remove cytokines from the blood of severely ill patients to prevent uncontrolled inflammation induced by a cytokine storm. This article discoveres, for the first time, that 2D Ti3C2T x MXene sheet demonstrates an ultrahigh removal capability for typical cytokine interleukin-6. In particular, MXene shows a 13.4 times higher removal efficiency over traditional activated carbon absorbents. Molecular-level investigations reveal that MXene exhibits a strong chemisorption mechanism for immobilizing cytokine interleukin-6 molecules, which is different from activated carbon absorbents. MXene sheet also demonstrates excellent blood compatibility without any deleterious side influence on the composition of human blood. This work can open a new avenue to use MXene sheets as an ultraefficient hemoperfusion absorbent to eliminate the cytokine storm syndrome in treatment of severe COVID-19 patients.

Polymyxin B engineered polystyrene-divinylbenzene microspheres for the adsorption of bilirubin and endotoxin

Hemoperfusion is an important strategy for liver disease treatment. Polystyrene-divinylbenzene (PS-DVB) microspheres are widely applied as absorbents in hemoperfusion to efficiently remove the important toxin bilirubin. However, as another common toxin, endotoxin will remain during this process and cause endotoxemia. Therefore, simultaneous removal of both bilirubin and endotoxin is highly desirable. In the present study, we engineered PS-DVB microspheres with polymyxin B sulfate (PMB) to meet this goal. After modification, the novel PMB-engineered (P-PMB) microspheres displayed excellent biocompatibility and hemocompatibility. Notably, compared to PS-DVB microspheres, P-PMB microspheres exhibited markedly stronger detoxification of both bilirubin and endotoxin, increasing by 17.03% and 42.57%, respectively. Overall, we believe that the novel P-PMB microspheres have considerable potential for liver disease treatment in clinical practice.

A new adsorbent for hemoperfusion was successfully prepared by grafting polymyxin B (PMB) on the surface of polystyrene divinylbenzene (PS-DVB) microspheres. It showed good biocompatibility and could adsorb both bilirubin and endotoxin.

Identification of blood plasma proteins using heparin-coated magnetic chitosan particles

Heparin was immobilized on magnetic chitosan particles to be used as a tool for human plasma protein identification. Chitosan was magnetized by co-precipitation with Fe²⁺/Fe³⁺ (MAG-CH). Heparin was functionalized with carbodiimide and N-hydroxysuccinimide and covalently linked to MAG-CH (MAG-CH-hep). X-ray diffraction confirmed the presence of chitosan and Fe₃O₄ in MAG-CH. This particle exhibited superparamagnetism and size between 100-300 μm. Human plasma diluted with 10 mM phosphate buffer (pH 5.5) or 50 mM Tris-HCl buffer (pH 8.5) was incubated with MAG-CH-hep, and the proteins fixed were eluted with the same buffers containing increasing concentrations of NaCl. The proteins obtained were investigated by SDS-PAGE, LC/MS, and biological activity tests (PT, aPTT, and enzymatic chromogenic assay). Inhibitors of the serpin family, prothrombin, and human albumin were identified in this study. Therefore, MAG-CH-hep can be used to purify these proteins and presents the following advantages: low-cost synthesis, magnetic separation, ion-exchange purification, and reusability.

Construction of Kevlar nanofiber/graphene oxide composite beads as safe, self-anticoagulant, and highly efficient hemoperfusion adsorbents

Recently emerged hemoperfusion absorbents, e.g. ion-exchange resin, activated carbon, and other porous materials, provide numerous novel possibilities to cure chronic liver failure (CLF) and renal failure (CRF). However, the limited adsorption performance and unsatisfactory blood compatibility significantly impede the development of the absorbents. Hence, designing safe and self-anticoagulant hemoperfusion absorbents with robust toxin clearance remains a considerable challenge. Here, brand new Kevlar-based composite gel beads for hemoperfusion are prepared by interface assembly based on π-π interaction. First, Kevlar nanofiber-graphene oxide (K-GO) beads are produced by liquid-liquid phase separation. Then, sodium p-styrenesulfonate (SS) is adsorbed onto the K-GO interface by π-π interaction and initiated to achieve the composite gel (K-GO/PSS) beads with an interfacial crosslinked structure. Such composite gel beads possess superior mechanical strength and self-anticoagulation capability, owing to the dual-network structure and heparin-mimicking gel structure, respectively. Furthermore, the K-GO/PSS beads show robust adsorption capacities for different kinds of toxins due to their strong charge and π-π interactions. A simulated hemoperfusion experiment in vitro demonstrates that the concentrations of the toxins in the blood can be restored to normal values within 30 minutes. In general, we envision that such composite gel beads will provide new strategies for future clinical CLF and CRF treatments.

Recent advances in heparinization of polymeric membranes for enhanced continuous blood purification

Continuous blood purification technology such as hemodiafiltration has been used worldwide for saving patients suffering from severe diseases or organ function failure, especially in the intensive care unit and emergency setting. The filters as core devices are commonly made of polymer materials as hollow fiber membranes. However, the membrane is often inductively blocked by blood clot formation due to its interactions with blood components. Heparin is the anticoagulant often used in clinical practice for anti-coagulation. Recently, heparin is also employed to modify the hollow fiber membranes either chemically or physically to improve the filtration performance. This review summarizes recent advances in methodology for surface heparinization of such hollow fiber membranes, and their filtration performance improvement. The review also provides expert opinions for further research in this rapidly expanding field.

Effects of polysiloxanes with different molecular weights on in vitro cytotoxicity and properties of polyurethane/cotton–cellulose nanofiber nanocomposite films

A series of polyurethane/cotton–cellulose nanofiber nanocomposite films are manufactured using amino-terminated polydimethylsiloxane, polycarbonate diol, isophorone diisocyanate, and dispersed cotton–cellulose nanofibers.