A comparison of covalent immobilization and physical adsorption of a cellulase enzyme mixture

Protecting Orthopaedic Implants from Infection: Antimicrobial Peptide Mel4 Is Non-Toxic to Bone Cells and Reduces Bacterial Colonisation When Bound to Plasma Ion-Implanted 3D-Printed PAEK Polymers

Even with the best infection control protocols in place, the risk of a hospital-acquired infection of the surface of an implanted device remains significant. A bacterial biofilm can form and has the potential to escape the host immune system and develop resistance to conventional antibiotics, ultimately causing the implant to fail, seriously impacting patient well-being. Here, we demonstrate a 4 log reduction in the infection rate by the common pathogen S. aureus of 3D-printed polyaryl ether ketone (PAEK) polymeric surfaces by covalently binding the antimicrobial peptide Mel4 to the surface using plasma immersion ion implantation (PIII) treatment. The surfaces with added texture created by 3D-printed processes such as fused deposition-modelled polyether ether ketone (PEEK) and selective laser-sintered polyether ketone (PEK) can be equally well protected as conventionally manufactured materials. Unbound Mel4 in solution at relevant concentrations is non-cytotoxic to osteoblastic cell line Saos-2. Mel4 in combination with PIII aids Saos-2 cells to attach to the surface, increasing the adhesion by 88% compared to untreated materials without Mel4. A reduction in mineralisation on the Mel4-containing surfaces relative to surfaces without peptide was found, attributed to the acellular portion of mineral deposition.

Cellulase immobilization to enhance enzymatic hydrolysis of lignocellulosic biomass: An all-inclusive review

Cellulase-mediated lignocellulosic biorefinery plays a crucial role in the production of high-value biofuels and chemicals, with enzymatic hydrolysis being an essential component. The advent of cellulase immobilization has revolutionized this process, significantly enhancing the efficiency, stability, and reusability of cellulase enzymes. This review offers a thorough analysis of the fundamental principles underlying immobilization, encompassing various immobilization approaches such as physical adsorption, covalent binding, entrapment, and cross-linking. Furthermore, it explores a diverse range of carrier materials, including inorganic, organic, and hybrid/composite materials. The review also focuses on emerging approaches like multi-enzyme co-immobilization, oriented immobilization, immobilized enzyme microreactors, and enzyme engineering for immobilization. Additionally, it delves into novel carrier technologies like 3D printing carriers, stimuli-responsive carriers, artificial cellulosomes, and biomimetic carriers. Moreover, the review addresses recent obstacles in cellulase immobilization, including molecular-level immobilization mechanism, diffusion limitations, loss of cellulase activity, cellulase leaching, and considerations of cost-effectiveness and scalability. The knowledge derived from this review is anticipated to catalyze the evolution of more efficient and sustainable biocatalytic systems for lignocellulosic biomass conversion, representing the current state-of-the-art in cellulase immobilization techniques.

Influence of elevated pressure and pressurized fluids on microenvironment and activity of enzymes

Enzymes have great potential in bioprocess engineering due to their green and mild reaction conditions. However, there are challenges to their application, such as enzyme extraction and purification costs, enzyme recovery, and long reaction time. Enzymatic reaction rate enhancement and enzyme immobilization have the potential to overcome some of these challenges. Application of high pressure (e.g., hydrostatic pressure, supercritical carbon dioxide) has been shown to increase the activity of some enzymes, such as lipases and cellulases. Under high pressure, enzymes undergo multiple alterations simultaneously. High pressure reduces the bond lengths of molecules of reaction components and causes a reduction in the activation volume of enzyme-substrate complex. Supercritical CO2 interacts with enzyme molecules, catalyzes structural changes, and removes some water molecules from the enzyme's hydration layer. Interaction of scCO2 with the enzyme also leads to an overall change in secondary structure content. In the extreme, such changes may lead to enzyme denaturation, but enzyme activation and stabilization have also been observed. Immobilization of enzymes onto silica and zeolite-based supports has been shown to further stabilize the enzyme and provide resistance towards perturbation under subjection to high pressure and scCO2.

Covalent and Non-covalent In-Flow Biofunctionalization for Capture Assays on Silicon Chips: White Light Reflectance Spectroscopy Immunosensor Combined with TOF-SIMS Resolves Immobilization Stability and Binding Stoichiometry

Immunosensors that combine planar transducers with microfluidics to achieve in-flow biofunctionalization and assay were analyzed here regarding surface binding capacity, immobilization stability, binding stoichiometry, and amount and orientation of surface-bound IgG antibodies. Two IgG immobilization schemes, by physical adsorption [3-aminopropyltriethoxysilane (APTES)] and glutaraldehyde covalent coupling (APTES/GA), followed by blocking with bovine serum albumin (BSA) and streptavidin (STR) capture, are monitored with white light reflectance spectroscopy (WLRS) sensors as thickness d_Γ of the adlayer formed on top of aminosilanized silicon chips. Multi-protein surface composition (IgG, BSA, and STR) is determined by time of flight secondary ion mass spectrometry (TOF-SIMS) combined with principal component analysis (applying barycentric coordinates to the score plot). In-flow immobilization shows at least 1.7 times higher surface binding capacity than static adsorption. In contrast to physical immobilization, which is unstable during blocking with BSA, chemisorbed antibodies desorb (reducing d_Γ) only when the bilayer is formed. Also, TOF-SIMS data show that IgG molecules are partially exchanged with BSA on APTES but not on APTES/GA modified chips. This is confirmed by the WLRS data that show different binding stoichiometry between the two immobilization schemes for the direct binding IgG/anti-IgG assay. The identical binding stoichiometry for STR capture results from partial replacement with BSA of vertically aligned antibodies on APTES, with fraction of exposed Fab domains higher than on APTES/GA.

Surface modified materials for active capture of enzymes

The insertion of bis(diarylcarbene)s onto a glass fiber (GF) membrane surface provided an active coating for the direct capture of protein - exemplified by the enzyme, cellulase - through a mild diazonium coupling process which does not require additional coupling agents. Successful cellulase attachment on the surface was demonstrated by the disappearance of diazonium and formation of azo functions in the N 1s high resolution spectra, the appearance of carboxyl group in C 1s spectra, both observed by XPS; the -CO vibrational bond observed by ATR-IR; as well as the observation of fluorescence. Further, five support materials (polystyrene XAD4 bead, polyacrylate MAC3 bead, glass wool, glass fiber membrane, polytetrafluoroethylene membrane) with different morphology and surface chemistry, were examined in detail as supports for cellulase immobilization using this common surface modification protocol. Of interest is that such covalently bound cellulase on modified GF membrane gave both the highest enzyme loading (∼23 mg cellulase per g support), and retained more than 90% of activity after 6 cycles of re-use, compared with substantial loss of enzyme activity for physiosorbed cellulase after 3 cycles. Optimization of the degree of surface grafting and the effectiveness of a spacer between surface and enzyme for enzyme loading and activity were conducted. This work shows that carbene surface modification is a viable strategy for introducing enzymes onto a surface under very mild conditions and retaining a meaningful level of activity, and particularly, using GF membrane as a novel support provides a potential platform for enzyme and protein immobilization.

Elastic Modulus of a Carbonized Layer on Polyurethane Treated by Ion-Plasma

Nanocoatings formed by various plasma and chemical methods on the surface of polymeric materials have unique properties. However, the applicability of polymeric materials with nanocoatings under specific temperature and mechanical conditions depends on the physical and mechanical properties of the coating. The determination of Young’s modulus is a task of paramount importance since it is widely used in calculations of the stress–strain state of structural elements and structures in general. Small thicknesses of nanocoatings limit the choice of methods for determining the modulus of elasticity. In this paper, we propose a method for determining the Young’s modulus for a carbonized layer formed on a polyurethane substrate. For its implementation, the results of uniaxial tensile tests were used. This approach made it possible to obtain patterns of change in the Young’s modulus of the carbonized layer depending on the intensity of ion-plasma treatment. These regularities were compared with regularities of changes in the molecular structure of the surface layer caused by plasma treatment of different intensity. The comparison was made on the basis of correlation analysis. Changes in the molecular structure of the coating were determined from the results of infrared Fourier spectroscopy (FTIR) and spectral ellipsometry.

Co-immobilization of Cellulase and β-Glucosidase into Mesoporous Silica Nanoparticles for the Hydrolysis of Cellulose Extracted from Eriobotrya japonica Leaves

Fungal cellulases generally contain a reduced amount of β-glucosidase (BG), which does not allow for efficient cellulose hydrolysis. To address this issue, we implemented an easy co-immobilization procedure of β-glucosidase and cellulase by adsorption on wrinkled mesoporous silica nanoparticles with radial and hierarchical open pore structures, exhibiting smaller (WSN) and larger (WSN-p) inter-wrinkle distances. The immobilization was carried out separately on different vectors (WSN for BG and WSN-p for cellulase), simultaneously on the same vector (WSN-p), and sequentially on the same vector (WSN-p) in order to optimize the synergy between cellulase and BG. The obtained results pointed out that the best biocatalyst is that prepared through simultaneous immobilization of BG and cellulase on the same vector (WSN-p). In this case, the adsorption resulted in 20% yield of immobilization, corresponding to an enzyme loading of 100 mg/g of support. 82% yield of reaction and 72 μmol/min·g activity were obtained, evaluated for the hydrolysis of cellulose extracted from Eriobotrya japonica leaves. All reactions were carried out at a standard temperature of 50 °C. The biocatalyst retained 83% of the initial yield of reaction after 9 cycles of reuse. Moreover, it had better stability than the free enzyme mixture in a wide range of temperatures, preserving 72% of the initial yield of reaction up to 90 °C.

Post-hydrolysis of cellulose oligomers by cellulase immobilized on chitosan-grafted magnetic nanoparticles: A key stage of butanol production from waste textile

The recently developed technologies for immobilization of cellulase may address the challenges in costly hydrolysis of cellulose for cellulosic butanol production. In this study, a "hybrid" hydrolysis was developed based on chemical hydrolysis of cellulose to its oligomers followed by enzymatic post-hydrolysis of the resulting "soluble oligomers" by cellulase immobilized on chitosan-coated Fe₃O₄ nanoparticles. This hybrid hydrolysis stage was utilized in the process of biobutanol production from a waste textile, jeans waste, leading to selective formation of glucose and high yield of butanol production by Clostridium acetobutylicum. After validating the immobilization process, the optimum immobilization parameters including enzyme concentration and time were achieved on 8 h and 15.0 mg/mL, respectively. The reusability of immobilized enzyme showed that immobilized cellulase could retain 51.5% of its initial activity after three times reuses. Dilute acid hydrolysis of regenerated cellulose at 120-180 °C for 60 min 0.5-1.0% phosphoric acid led to less than 10 g/L glucose production, and enzymatic post-hydrolysis of the oligomers resulted in up to 51.5 g/L glucose. Fermentation of the hydrolysate was accompanied by 5.3 g/L acetone-butanol-ethanol (ABE) production. The simultaneous co-saccharification and fermentation (SCSF) of soluble and insoluble oligomers of cellulose led to 17.4 g/L ABE production.

Preparation and characterization of stable core/shell Fe3O4@Au decorated with an amine group for immobilization of lipase by covalent attachment

The self-assembly approach was used for amine decoration of core/shell Fe₃O₄@Au with 4-aminothiophenol. This structure was used for covalent immobilization of lipase using a Ugi 4-component reaction. The amine group on the structure and carboxylic group from lipase can react in the Ugi reaction and a firm and stable covalent bond is created between enzyme and support. The synthesized structure was fully characterized and its activity was explored in different situations. The results showed the pH and temperature stability of immobilized lipase compared to free lipase in a wide range of pH and temperature. Also after 60 days, it showed excellent activity while residual activity for the free enzyme was only 10%. The synthesized structure was conveniently separated using an external magnetic field and reused 6 times without losing the activity of the immobilized enzyme.

The self-assembly approach was used for amine decoration of core/shell Fe₃O₄@Au with 4-aminothiophenol.

Dual enzyme co-immobilization on reversibly soluble polymers for the one-pot conversion of ferulic acid from wheat bran

The difficulty of using immobilized enzyme to decompose wheat bran to produce ferulic acid lies in the recovery of enzyme from solid-rich wheat bran hydrolysates. In this study, two enzymes...

Biomimetic reusable microfluidic reactors with physically immobilized RuBisCO for glucose precursor production

Reusable RuBisCO-immobilized microfluidic reactors are used to synthesize the glucose precursor from CO2 and restore >95% of activity after refreshing.

Formulations for Bacteriophage Therapy and the Potential Uses of Immobilization

The emergence of antibiotic-resistant pathogens is becoming increasingly problematic in the treatment of bacterial diseases. This has led to bacteriophages receiving increased attention as an alternative form of treatment. Phages are effective at targeting and killing bacterial strains of interest and have yielded encouraging results when administered as part of a tailored treatment to severely ill patients as a last resort. Despite this, success in clinical trials has not always been as forthcoming, with several high-profile trials failing to demonstrate the efficacy of phage preparations in curing diseases of interest. Whilst this may be in part due to reasons surrounding poor phage selection and a lack of understanding of the underlying disease, there is growing consensus that future success in clinical trials will depend on effective delivery of phage therapeutics to the area of infection. This can be achieved using bacteriophage formulations instead of purely liquid preparations. Several encapsulation-based strategies can be applied to produce phage formulations and encouraging results have been observed with respect to efficacy as well as long term phage stability. Immobilization-based approaches have generally been neglected for the production of phage therapeutics but could also offer a viable alternative.

The Role of Surface Chemistry in the Efficacy of Protein and DNA Microarrays for Label-Free Detection: An Overview

The importance of microarrays in diagnostics and medicine has drastically increased in the last few years. Nevertheless, the efficiency of a microarray-based assay intrinsically depends on the density and functionality of the biorecognition elements immobilized onto each sensor spot. Recently, researchers have put effort into developing new functionalization strategies and technologies which provide efficient immobilization and stability of any sort of molecule. Here, we present an overview of the most widely used methods of surface functionalization of microarray substrates, as well as the most recent advances in the field, and compare their performance in terms of optimal immobilization of the bioreceptor molecules. We focus on label-free microarrays and, in particular, we aim to describe the impact of surface chemistry on two types of microarray-based sensors: microarrays for single particle imaging and for label-free measurements of binding kinetics. Both protein and DNA microarrays are taken into consideration, and the effect of different polymeric coatings on the molecules' functionalities is critically analyzed.

Enzyme-driven micro/nanomotors: Recent advances and biomedical applications

Micro/nanomotors (MNMs), both self-propelled actuators and external fields-promoted machines, have joined forces in the past decade to accomplish versatile tasks such as precise detection and targeted cargo delivery with adequate propulsion and desirable locomotion. Amongst, enzyme-driven MNMs have been able to differentiate themselves from others owing to their distinct characteristics, such as absence of chemical fuel, enhanced cellular uptake and the possibility to be easily conjugated with many therapeutics, including both small molecules and biologics, displaying superior efficacy, enhanced specificity and diminished side effects. In the present review, we aim to highlight and summarize recent advances in enzyme-driven MNMs, particularly to provide an in-depth discussion focusing on the enzyme linking approaches onto those MNMs and motion control strategies of such MNMs with advantages and limitations thereof. Conclusions and future perspectives are also provided in brief.

Covalent Immobilization of N-Acetylcysteine on a Polyvinyl Chloride Substrate Prevents Bacterial Adhesion and Biofilm Formation

Biofilm formation and antimicrobial resistance at surgical implant sites result in high morbidity and mortality. Identifying novel molecules that inhibit biofilm formation to coat surgical biomaterials is essential. One such compound is N-acetylcysteine (NAC), a potent antioxidant precursor for glutathione, necessary in mammalian cells and known to disrupt/prevent biofilms. In this study, NAC was covalently immobilized onto functionalized polyvinyl chloride surfaces using plasma immersion ion implantation (PIII) treatment that achieves covalent binding without the need for linker groups. NAC immobilization was characterized using water contact angles, Fourier-transform infrared, and X-ray photoelectron spectroscopy techniques. Bacterial viability and biofilm formation on NAC surfaces were assessed using resazurin assays, phase contrast microscopy, and colony counting experiments. Effect of NAC on bacterial polysaccharide production and DNA cleaving was investigated using the phenol-sulfuric acid method and the Qubit fluorometer. Surface thermodynamics between the NAC coating and bacterial cells were measured using the Lewis acid-base method. Surface characterization techniques demonstrated superficial changes after PIII treatment and subsequent covalent NAC immobilization. NAC-coated surfaces significantly reduced biofilm viability and the presence of Gram-negative and Gram-positive bacteria. NAC also decreased polysaccharide production and degraded DNA. This led to unfavorable conditions for biofilm formation on NAC-coated surfaces, as demonstrated by surface thermodynamic analysis. NAC-coated surfaces showed no cytotoxicity to human fibroblast cells. This study has successfully utilized NAC as an antibiofilm coating, which may pave the way for improved prophylactic coatings on medical implant devices in the future.

Adsorption of Cellulase on Wrinkled Silica Nanoparticles with Enhanced Inter-Wrinkle Distance

Mesoporous silica materials offer a unique opportunity for enzyme immobilization thanks to their properties, such as tuneable pore size, large surface area and easy functionalization. However, a significant enhancement of cellulase enzyme activity entrapped inside the silica pores still represents a challenge. In this work, we immobilized cellulase by adsorption on wrinkled silica nanoparticles (WSNs), obtaining an active and stable biocatalyst. We used pentanol as co-solvent to synthesize WSNs with enhanced inter-wrinkle distance in order to improve cellulase hosting. The physical-chemical and morphological characterization of WSNs and cellulase/WSNs was performed by thermogravimetric (TG), Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) analyses. The obtained results showed that this matrix generates a favourable microenvironment for hosting cellulase. The results of the catalytic assays and operational stability confirmed the key role of size, morphology and distribution of the pores in the successful outcome of the cellulase immobilization process. The immobilization procedure used allowed preserving most of the secondary structure of the enzyme and, consequently, its catalytic activity. Moreover, the same value of glucose yield was observed for five consecutive runs, showing a high operational stability of the biocatalyst.

Covalent Biofunctionalization of the Inner Surfaces of a Hollow-Fiber Capillary Bundle Using Packed-Bed Plasma Ion Implantation

Hollow-fiber capillary bundles are widely used in the production of medical devices for blood oxygenation and purification purposes such as in cardiopulmonary bypass, hemodialysis, and hemofiltration, but the blood interfacing inner surfaces of these capillaries provide poor hemocompatibility. Here, we present a novel method of packed-bed plasma ion implantation (PBPII) for the modification of the inner surfaces of polymeric hollow-fiber bundles enclosed in a cassette. The method is simple and can be performed on an intact hollow-fiber bundle cassette by the placement of a hollow cylindrical electrode, connected to a negative high-voltage pulse generator, around the cassette. The method does not require the insertion of electrodes inside the capillaries or the cassette. Nitrogen gas is fed into the capillaries inside the cassette by connecting the inlet of the cassette to a gas source. Upon the application of negative high-voltage bias pulses to the electrode, plasma is ignited inside the cassette, achieving the surface modification of both the internal and external surfaces of the capillaries. Fourier transform infrared-attenuated total reflectance spectroscopy of the PBPII-treated capillaries revealed the formation of aromatic C═C bonds, indicating the progressive carbonization of the capillary surfaces. The PBPII treatment was found to be uniform along the capillaries and independent of the radial position in the cassette. Atomic force microscopy of cross sections through the capillaries revealed that the increased stiffness associated with the carbonized layer on the inner surface of the PBPII-treated capillary has a depth (∼40 nm) consistent with that expected for ions accelerated by the applied bias voltage. The modified internal surfaces of the capillary bundle showed a greatly increased wettability and could be biofunctionalized by covalently immobilizing protein directly from the buffer solution. The direct, reagent-free protein immobilization was demonstrated using tropoelastin as an example protein. Covalent binding of the protein was confirmed by its resistance to removal by hot sodium dodecyl sulfate detergent washing, which is known to disrupt physical binding.

Glycoside hydrolase (PelAh) immobilization prevents Pseudomonas aeruginosa biofilm formation on cellulose-based wound dressing

Bacterial cellulose (BC) is recognized as a wound dressing material well-suited for chronic wounds; however, it has no intrinsic antimicrobial activity. Further, the formation of biofilms can limit the effectiveness of the pre-saturation of BC with antimicrobial agents. Here, to hinder biofilm formation by P. aeruginosa, we immobilized the hydrolytic domain of PelA (a glycohydrolase involved in the synthesis of biofilm polysaccharide Pel) on the surface of BC. The immobilization of 32.35 ± 1.05 mg PelA_h per g BC membrane resulted in an eight-fold higher P. aeruginosa cell detachment from BC membrane, indicating reduced biofilm matrix stability. Further, 1D and 2D infrared spectroscopy analysis indicated systematic reduction of polysaccharide biofilm elements, confirming the specificity of immobilized PelA_h. Importantly, BC-PelA_h was not cytotoxic towards L929 fibroblast cells. Thus, we conclude that PelA_h can be used in BC wound dressings for safe and specific protection against biofilm formation by P. aeruginosa.

Gold, Silver and Iron Oxide Nanoparticles: Synthesis and Bionanoconjugation Strategies Aimed at Electrochemical Applications

Nanomaterials have revolutionized the sensing and biosensing fields, with the development of more sensitive and selective devices for multiple applications. Gold, silver and iron oxide nanoparticles have played a particularly major role in this development. In this review, we provide a general overview of the synthesis and characteristics of gold, silver and iron oxide nanoparticles, along with the main strategies for their surface functionalization with ligands and biomolecules. Finally, different architectures suitable for electrochemical applications are reviewed, as well as their main fabrication procedures. We conclude with some considerations from the authors' perspective regarding the promising use of these materials and the challenges to be faced in the near future.

Investigation of nanoparticle immobilized cellulase: nanoparticle identity, linker length and polyphenol hydrolysis

Cellulase containing nanobiocatalysts have been useful as an extraction tool based on their ability to disrupt plant cell walls. In this work, we investigate the effect of nanoparticle composition and chemical linkage towards immobilized cellulase activity. Cellulase nanoconstructs have been prepared, characterized and compared for their loading efficiencies with standard assays and enzyme kinetics and correlate well with the cognate loading efficiencies. Application of the cellulase-immobilized nanoparticles on onion skins results in release of a distinctive composition of polyphenols. The aglycosidic form of quercetin is the dominant product of onion skin hydrolysis affected by cellulase nanobiocatalysts. Chitosan-coated iron oxide nanoparticles with APTES-conjugated cellulase are found to be most effective for polyphenol release and for transformation of glycosidic to aglycosidic form of quercetin. These results shed light on the activity of immobilized cellulase beyond their role in cell wall disruption and are important for the practical application of cellulase nanobiocatalysts.

Stabilization of Formate Dehydrogenase in a Metal-Organic Framework for Bioelectrocatalytic Reduction of CO2

The efficient fixation of excess CO₂ from the atmosphere to yield value-added chemicals remains crucial in response to the increasing levels of carbon emission. Coupling enzymatic reactions with electrochemical regeneration of cofactors is a promising technique for fixing CO₂ , while producing biomass which can be further transformed into biofuels. Herein, a bioelectrocatalytic system was established by depositing crystallites of a mesoporous metal-organic framework (MOF), termed NU-1006, containing formate dehydrogenase, on a fluorine-doped tin oxide glass electrode modified with Cp*Rh(2,2'-bipyridyl-5,5'-dicarboxylic acid)Cl₂ complex. This system converts CO₂ into formic acid at a rate of 79±3.4 mm h^-1 with electrochemical regeneration of the nicotinamide adenine dinucleotide cofactor. The MOF-enzyme composite exhibited significantly higher catalyst stability when subjected to non-native conditions compared to the free enzyme, doubling the formic acid yield.

Covalent Immobilization of Cellulase Using Magnetic Poly(ionic liquid) Support: Improvement of the Enzyme Activity and Stability

A magnetic nanocomposite was prepared by entrapment of Fe₃O₄ nanoparticles into the cross-linked ionic liquid/epoxy type polymer. The resulting support was used for covalent immobilization of cellulase through the reaction with epoxy groups. The ionic surface of the support improved the adsorption of enzyme, and a large amount of enzyme (106.1 mg/g) was loaded onto the support surface. The effect of the presence of ionic monomer and covalent binding of enzyme was also investigated. The structure of support was characterized by various instruments such as FT-IR, TGA, VSM, XRD, TEM, SEM, and DLS. The activity and stability of immobilized cellulase were investigated in the prepared support. The results showed that the ionic surface and covalent binding of enzyme onto the support improved the activity, thermal stability, and reusability of cellulase compared to free cellulase.

Cellulose as a template to fabricate a cellulase-immobilized composite with high bioactivity and reusability

Herein, a new strategy was developed to fabricate an oriented cellulase/chitosan/Fe₃O₄composite, which possesses extremely high activity, reusability, and stability.

Plasma activated coating immobilizes apolipoprotein A-I to stainless steel surfaces in its bioactive form and enhances biocompatibility

We utilized a plasma activated coating (PAC) to covalently bind the active component of high density lipoproteins (HDL), apolipoprotein (apo) A-I, to stainless steel (SS) surfaces. ApoA-I suppresses restenosis and thrombosis and may therefore improve SS stent biocompatibility. PAC-coated SS significantly increased the covalent attachment of apoA-I, compared to SS alone. In static and dynamic flow thrombosis assays, PAC+apoA-I inhibited thrombosis and reduced platelet activation marker p-selectin. PAC+apoA-I reduced smooth muscle cell attachment and proliferation, and augmented EC attachment to PAC. We then coated PAC onto murine SS stents and found it did not peel or delaminate following crimping/expansion. ApoA-I was immobilized onto PAC-SS stents and was retained as a monolayer when exposed to pulsatile flow in vivo in a murine stent model. In conclusion, ApoA-I immobilized on PAC withstands pulsatile flow in vivo and retains its bioactivity, exhibiting anti-thrombotic and anti-restenotic properties, demonstrating the potential to improve stent biocompatibility.

Free-Radical-Induced Grafting from Plasma Polymer Surfaces

With the advances in science and engineering in the second part of the 20th century, emerging plasma-based technologies continuously find increasing applications in the domain of polymer chemistry, among others. Plasma technologies are predominantly used in two different ways: for the treatment of polymer substrates by a reactive or inert gas aiming at a specific surface functionalization or for the synthesis of a plasma polymer with a unique set of properties from an organic or mixed organic-inorganic precursor. Plasma polymer films (PPFs), often deposited by plasma-enhanced chemical vapor deposition (PECVD), currently attract a great deal of attention. Such films are widely used in various fields for the coating of solid substrates, including membranes, semiconductors, metals, textiles, and polymers, because of a combination of interesting properties such as excellent adhesion, highly cross-linked structures, and the possibility of tuning properties by simply varying the precursor and/or the synthesis parameters. Among the many appealing features of plasma-synthesized and -treated polymers, a highly reactive surface, rich in free radicals arising from deposition/treatment specifics, offers a particular advantage. When handled carefully, these reactive free radicals open doors to the controllable surface functionalization of materials without affecting their bulk properties. The goal of this review is to illustrate the increasing application of plasma-based technologies for tuning the surface properties of polymers, principally through free-radical chemistry.

Immunosensor for the ultrasensitive and quantitative detection of bladder cancer in point of care testing

An ultrasensitive and real-time impedance based immunosensor has been fabricated for the quantitative detection of Galectin-1 (Gal-1) protein, a biomarker for the onset of multiple oncological conditions, especially bladder cancer. The chip consists of a gold annular interdigitated microelectrode array (3×3 format with a sensing area of 200µm) patterned using standard microfabrication processes, with the ability to electrically address each electrode individually. To improve sensitivity and immobilization efficiency, we have utilized nanoprobes (Gal-1 antibodies conjugated to alumina nanoparticles through silane modification) that are trapped on the microelectrode surface using programmable dielectrophoretic manipulations. The limit of detection of the immunosensor for Gal-1 protein is 0.0078mg/ml of T24 (Grade III) cell lysate in phosphate buffered saline, artificial urine and human urine samples. The normalized impedance variations show a linear dependence on the concentration of cell lysate present while specificity is demonstrated by comparing the immunosensor response for two different grades of bladder cancer cell lysates. We have also designed a portable impedance analyzing device to connect the immunosensor for regular checkup in point of care testing with the ability to transfer data over the internet using a personal computer. We believe that this diagnostic system would allow for improved public health monitoring and aid in early cancer diagnosis.