Bioactive bacterial cellulose sulfate electrospun nanofibers for tissue engineering applications

Cellulosic materials have been of tremendous importance to mankind since its discovery due to its superior properties and its abundance in nature. Recently, an increase in demand for alternate green materials has rekindled the interest for cellulosic materials. Here, bacterial cellulose has been functionalized with sulfate groups through acetosulfation to gain solubility in aqueous media, which provides access to several applications. The cell viability, antioxidant, and hemocompatibility assays have verified the biocompatible and antioxidant characteristics of bacterial cellulose sulfate (BCS) in both in vitro and ex vivo conditions. Further, novel BCS/polyvinyl alcohol nanofibers were fabricated by simple electrospinning route to engineer ultrafine nanoscale fibers. The biological evaluation of BCS/polyvinyl alcohol nanofiber scaffolds was done using L929 mouse fibroblast cells, which confirmed that these nanofibers are excellent matrices for cell adhesion and proliferation.     

Insights into the metal retention role in the antibacterial behavior of montmorillonite and cellulose tissue-supported copper and silver nanoparticles

The role of the retention strength of Cu⁰ and Ag⁰ nanoparticles on the induced antibacterial properties of montmorillonite and cellulose-supported polyol dendrimer was comparatively investigated. An unprecedented approach involving X-ray photoelectron spectroscopy, thermal analyses, and surface charge measurements allowed correlating the host–matrix features to the different antibacterial activities of Cu⁰ and Ag⁰ nanoparticles against both the bacterial strains. Optimal metal–matrix interactions appear to favor high dispersion of both metal particles and material grains, thereby improving the contact surface with the cultivation media. This was explained in terms of hydrophilic character and judicious compromise between the metal retention by the host–matrix and release in the impregnating media. Competitive Lewis acid–base interactions appear to occur between MNP, solid surface and liquid media. These findings are of great importance, providing a deeper understanding of the antibacterial activity of metal-loaded materials. This opens promising prospects for vegetal fibers and clay-supported drugs to treat dermatological and gastro-intestinal infections.

The role of the retention strength of Cu⁰ and Ag⁰ nanoparticles on the induced antibacterial properties of montmorillonite and cellulose-supported polyol dendrimer against Escherichia coli DH5α and Bacillus subtilis 168 was comparatively investigated.     

Hybrids based on borate-functionalized cellulose nanofibers and noble-metal nanoparticles as sustainable catalysts for environmental applications

Polymeric supports from renewable resources such as cellulose nanomaterials are having a direct impact on the development of heterogenous sustainable catalysts. Recently, to increase the potentiality of these materials, research has been oriented towards novel functionalization possibilities. In this study, to increase the stability of cellulose nanofiber films as catalytic supports, by limiting the solubility in water, we report the synthesis of new hybrid catalysts (HC) based on silver, gold, and platinum nanoparticles, and the corresponding bimetallic nanoparticles, supported on cellulose nanofibers (CNFs) cross-linked with borate ions. The catalysts were prepared from metal precursors reduced by the CNFs in an aqueous suspension. Metal nanoparticles supported on CNFs with a spherical shape and a mean size of 9 nm were confirmed by TEM, XRD, and SAXS. Functionalized films of HC-CNFs were obtained by adding a borate solution as a cross-linking agent. Solid-state ¹¹B NMR of films with different cross-linking degrees evidenced the presence of four different boron species of which the bis-chelate is responsible for the cross-linking of the CNFs. Also, it may be concluded that the bis-chelate and the mono-chelates modify the microstructure of the film increasing the water uptake and enhancing the catalytic activity in the reduction of 4-nitrophenol.

We report the synthesis of supported noble metal nanoparticles on cellulose nanofibers cross-linked with borate as highly efficient sustainable catalysts.     

Anhydrous proton conductivity of electrospun phosphoric acid-doped PVP-PVDF nanofibers and composite membranes containing MOF fillers

A high-temperature proton exchange membrane was fabricated based on polyvinylidene fluoride (PVDF) and polyvinylpyrrolidone (PVP) blend polymer nanofibers. Using electrospinning method, abundant small ionic clusters can be formed and agglomerated on membrane surface, which would facilitate the proton conductivity. To further enhance the conductivity, phosphoric acid (PA) retention as well as mechanical strength, sulfamic acid (SA)-doped metal–organic framework MIL-101 was incorporated into PVP-PVDF blend nanofiber membranes. As a result, the anhydrous proton conductivity of the composite SA/MIL101@PVP-PVDF membrane reached 0.237 S cm⁻¹ at 160 °C at a moderate acid doping level (ADL) of 12.7. The construction of long-range conducting network by electrospinning method combined with hot-pressing and the synergistic effect between PVP-PVDF, SA/MIL-101 and PA all contribute to the proton conducting behaviors of this composite membrane.

A composite SA/MIL101@PVP-PVDF membrane was fabricated via electrospinning and reached a conductivity of 0.237 S cm⁻¹ at 160 °C with a moderate acid doping level (12.7).     

Preparation of cellulose acetate derived carbon nanofibers by ZnCl2 activation as a supercapacitor electrode

Porous carbon nanofibers are fabricated by one-step carbonization and activation of electrospun cellulose acetate (CA) nanofibres. Electrospun CA nanofibers were obtained by the electrospinning of a CA/DMAC/acetone solution, followed by deacetylation in NaOH/ethanol solution. One-step carbonization and activation was achieved by dipping the as-spun fibers in ZnCl₂ solution, followed by one-step high temperature treatment. The effects of the concentration of the dipping solution on the microstructure of the CA-based carbon nanofibers (CACNFs), including the morphology, crystal structure, porous structure, specific surface area and surface chemical properties, have been investigated. The coating of ZnCl₂ effectively improves the thermal stability of electrospun CA nanofibers and obviously enhances the oxygen-containing surface groups of the CACNFs. The CACNFs have a norrow pore size distribution (0.6–1.2 nm) and a high specific surface area (∼1188 m² g⁻¹). Electrochemical performances of the CACNFs were evaluated as supercapacitor electrodes in 6 M KOH solution. The CACNFs demonstrate high specific capacitance (202 F g⁻¹ at 0.1 A g⁻¹) and excellent rate capability (61% of the retention from 0.1 to 20 A g⁻¹). After 5000 cycles of the electrode, the capacitance is maintained at 92%, and the coulombic efficiency is close to 100%, showing high electrochemical stability and reversibility. The renewable features and excellent performance make CACNFs quite a promising alternative to efficient supercapacitor electrodes for energy storage applications.

Porous carbon nanofibers are fabricated by one-step carbonization and activation of electrospun cellulose acetate (CA) nanofibres.     

Rapid and highly sensitive colloidal silver staining on cellulose acetate membrane for analysis of urinary proteins

In order to establish a rapid staining method sensitive enough to stain the protein bands on cellulose acetate membrane and suitable for the analysis of urinary proteins in healthy subjects, we conducted a detailed examination of Kovarik's method designed for the analysis of proteins in cerebrospinal fluid in detail. For purpose of our study, we changed the pH of the staining solution used in Kovarik's method to pH 4.4 by adding acetic acid. With this solution, our staining method revealed a degree of sensitivity about three times higher than that of the original method, but specific sensitivity for albumin and γ-globulin remained almost unchanged. The solution preparation we used was much more simple and the reagent much more stable than in the original method. Our method also showed better reproducibility and linearity than the original method. These results point to the suitability of this method for the analysis of low-concentration proteins, such as urinary proteins, in healthy subjects. © 1996 Wiley-Liss, Inc.     

Exploring corrosion protection properties of alkyd@lanthanide bis-phthalocyanine nanocomposite coatings

Organic coatings have been widely used to protect carbon steel pipelines from external corrosion; however, they often suffer from permeability and weak adhesion. Here we show that synthetic lanthanide bis-phthalocyanine complexes, LnPc₂ (Ln = lanthanide metal, Pc = C₃₂H₁₆N₈ denotes the phthalocyanine ligand) can be used to form new nanocomposite coatings to provide corrosion protection to the underlying carbon steel pipelines. Electrochemical studies (EIS and potentiodynamic polarization) showed that the incorporation of LnPc₂ compound (PrPc₂, SmPc₂ and HoPc₂) additives with alkyd coating, leads to a significant increase in the corrosion resistance of carbon steel in 0.5 M HCl solution. The alkyd@LnPc₂ nanocomposite coatings absorb very low water volumes, when compared to the neat alkyd coating. LnPc₂ compounds allowed enhancing the pull-off adhesion of coatings performance from 3.34 MPa to 19.94 MPa. The efficiency of alkyd@HoPc₂ coating appears higher than that of alkyd@PrPc₂ and alkyd@SmPc₂ coatings. The protective properties of alkyd@LnPc₂ coatings were confirmed by SEM, TGA, scratch hardness, impact resistance, bend test and contact angle analysis.

Organic coatings have been widely used to protect carbon steel pipelines from external corrosion; however, they often suffer from permeability and weak adhesion.     

Antibacterial properties of electrospun Ti3C2Tz (MXene)/chitosan nanofibers

Electrospun natural polymeric bandages are highly desirable due to their low-cost, biodegradability, non-toxicity and antimicrobial properties. Functionalization of these nanofibrous mats with two-dimensional nanomaterials is an attractive strategy to enhance the antibacterial effects. Herein, we demonstrate an electrospinning process to produce encapsulated delaminated Ti₃C₂T_z (MXene) flakes within chitosan nanofibers for passive antibacterial wound dressing applications. In vitro antibacterial studies were performed on crosslinked Ti₃C₂T_z/chitosan composite fibers against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) – demonstrating a 95% and 62% reduction in colony forming units, respectively, following 4 h of treatment with the 0.75 wt% Ti₃C₂T_z – loaded nanofibers. Cytotoxicity studies to determine biocompatibility of the nanofibers indicated the antibacterial MXene/chitosan nanofibers are non-toxic. The incorporation of Ti₃C₂T_z single flakes on fiber morphology was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy equipped with an energy-dispersive detector (TEM-EDS). Our results suggest that the electrospun Ti₃C₂T_z/chitosan nanofibers are a promising candidate material in wound healing applications.

Electrospun natural polymeric bandages are highly desirable due to their low-cost, biodegradability, non-toxicity and antimicrobial properties.     

DNA-binding,antioxidant, H2O2 sensing and photocatalytic properties of biogenic silver nanoparticles using Ageratum conyzoides L. leaf extract

Green nanotechnology is gaining widespread interest owing to the elimination of harmful reagents and offers a cost-effective synthesis of expected products. In the present study, silver nanoparticles (AgNPs) were synthesized from Ageratum conyzoides leaf extract (ACLE). UV-visible spectrophotometry showing a characteristic SPR peak at 443 nm verified the phytosynthesis of AC-AgNPs. The FTIR spectrum was examined to identify the efficient functional molecules responsible for the reduction of Ag⁺ to metallic silver (Ag⁰). SEM, TEM and XRD illustrated the formation of crystalline and spherical NPs with a size range of 14–48 nm. EDX data showed the presence of elemental silver with an energy peak at 3 eV. CT-DNA interaction with AC-AgNPs was investigated and the UV absorption spectra revealed a bathochromic effect indicating groove binding. AC-AgNPs showed a strong antioxidant property in a concentration-dependent manner when analyzed by DPPH and ABTS radical scavenging assay. AC-AgNPs were investigated as a SPR-based H₂O₂ sensor, which can provide promising opportunities in medical and environmental fields to detect reactive oxygen species such as H₂O₂. The catalytic effectiveness of phytosynthesized NPs was also examined within 2 h of exposure for methylene blue degradation under sunlight. There is thus a reasonable potential application of green synthesized AC-AgNPs for the degradation of hazardous synthetic dyes.

Green nanotechnology is gaining widespread interest owing to the elimination of harmful reagents and offers a cost-effective synthesis of expected products.     

Robust immobilization of anionic silver nanoparticles on cellulose filter paper toward a low-cost point-of-use water disinfection system with improved anti-biofouling properties

Silver nanoparticle (AgNP)-decorated cellulose filter paper (FP), a low-cost point-of-use (POU) water disinfection system, can supply affordable and safe drinking water for people in desperate need, especially in rural areas in developing countries. However, owing to the unstable immobilization of AgNPs, silver can leach into the treated drinking water from the FP and exceed the World Health Organization (WHO) drinking water limit (<100 μg L⁻¹), which is a potential threat to both human health and the environment. In this work, in order to robustly immobilize anionic silver nanoparticles (GA@AgNPs), we facilely prepared lipoic acid-modified cellulose filter paper (LA-FP), in which GA@AgNPs were robustly immobilized onto filter paper (GA@AgNPs-LA-FP) by strong chelation via the disulfide bond of LA with the surface of the silver nanoparticles. GA@AgNPs-LA-FP exhibited both excellent bacterial anti-adhesion activity and strong bactericidal activity, which can synergistically mitigate biofouling by inhibiting biofilm formation on the paper surface. Moreover, employed as a gravity-driven bactericidal filter, the GA@AgNPs-LA-FP membrane treated 100 mL of river water within 10 min, and the resulting water quality met the WHO drinking water standards, indicating this material''s practical application for POU water disinfection.

Point-of-use water disinfection by GA@AgNPs-LA-FP.     

Catalytic and anti-bacterial properties of biosynthesized silver nanoparticles using native inulin

Silver nanoparticles (Ag NPs) were green synthesized using native inulin as the reducing and capping agent with varied incubation temperatures, incubation times and Ag⁺ concentrations. The biosynthesized Ag NPs were characterized using UV-visible spectroscopy, Field Emission Transmission Electron Microscopy (FE-TEM) and X-ray powder diffraction. The UV visible spectra of the Ag NPs revealed a characteristic surface plasmon resonance peak at 420 nm. FE-TEM showed that the biosynthesized Ag NPs were spherically shaped and monodispersed nanoparticles. The sizes were 18.5 ± 0.9 nm and 20.0 ± 1.2 nm for the Ag NPs synthesized at 80 °C and 100 °C for 2 h using 0.1% inulin and 2 mM Ag⁺. Their PDIs were 0.180 ± 0.05 and 0.282 ± 0.13, respectively. Improving the incubation temperature, incubation time and silver nitrate concentration promoted Ag NP synthesis. The prepared Ag NPs were effective in the catalytic reduction of 4-NP and in inhibiting the growth of bacteria. The inhibition zone could reach 10.21 ± 2.12 mm and 9.92 ± 0.50 mm for Escherichia coli and Staphylococcus aureus. The kinetic rate constant (k_app) could reach 0.0113 s⁻¹, and the maximum inhibitory zones were 10.21 ± 2.12 mm and 9.92 ± 0.50 mm, respectively, for the two microorganisms. This biosynthesis illustrates that native inulin could be a potential candidate in the green fabrication of Ag NPs, and this is promising in catalytic and bacteriostatic fields.

Silver nanoparticles (Ag NPs) were green synthesized using native inulin as the reducing and capping agent with varied incubation temperatures, incubation times and Ag⁺ concentrations.     

Effect of a direct sulfonation reaction on the functional properties of thermally-crosslinked electrospun polybenzoxazine (PBz) nanofibers

Electrospun nanofibers of polybenzoxazines (PBzs) were fabricated using an electrospinning process and crosslinked by a sequential thermal treatment. Functionalization by the direct sulfonation process followed after the post-electrospinning modification treatment. The first stage of experiment determined the effects of varying the concentration of sulfuric acid as the sulfonating agent in the sulfonation reaction under ordinary conditions. The second stage examined the mechanism and kinetics of the sulfonation reaction using only concentrated H₂SO₄ at different reaction time periods of 3 h, 6 h, and 24 h. The mechanism of the sulfonation reaction with PBz nanofibers was proposed with only one sulfonic acid (–SO₃H) group attached to each of the repeating units since only first type substitution in the aromatic structure occurs under this condition. The kinetics of the reaction exhibited a logarithmic correlation where the rate of change in the ion exchange capacity (IEC) with the reaction time increased rapidly and then reached a plateau at the reaction time between 18 h and 24 h. Effective sulfonation was confirmed by electron spectroscopy with a characteristic peak associated with the C–S bond owing to the sulfonate group introduced onto the surface of the nanofibers. ATR-FTIR spectroscopy also confirmed these results for varying reaction times. The SEM images showed that sulfonation has no drastic effects on the morphology and microstructure of the nanofibers but a rougher surface was evident due to the wetted fibers with sulfonate groups attached to the surface. EDX spectra exhibited sulfur peaks where the concentration of sulfonate groups present in the nanofibers is directly proportional to the reaction time. From surface wettability studies, it was found that the nanofibers retained the hydrophobicity after sulfonation but the inherent surface property of PBz nanofibers was observed by changing the pH level of water to basic, which switches its surface properties to hydrophilic. The thermal stability of the sulfonated nanofibers showed almost the same behavior compared to non-sulfonated nanofibers except for the 24 h sulfonation case, which has slightly lower onset temperature of degradation.

Functionalization of PBz by electrospinning of nanofibers then thermal crosslinking followed by direct sulfonation process.     

Preparation and catalytic properties of polydopamine-modified polyacrylonitrile fibers functionalized with silver nanoparticles

Fiber-supported catalysts have attracted much attention due to their large specific surface area, high catalytic activity, and good recyclability. Functional polyacrylonitrile fibers were prepared by immersion of polyacrylonitrile fibers at room temperature in an alkaline dopamine (pH = 8.5) aqueous solution which can undergo self-polymerization and reduce silver ions to silver nanoparticles with mild reducibility and adsorption. The surface of the polyacrylonitrile fiber (PAN) was wrapped with a layer of polydopamine (PDA), and silver nanoparticles (Ag NPs) were adsorbed on the surface of PDA, forming an efficient fiber catalyst. The morphology and chemical composition of the catalyst material were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) patterns, and Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The catalytic activity of the nanocomposite was evaluated for the reduction reaction of 4-nitrophenol using sodium borohydride (NaBH₄) at 35 °C with a material molar ratio of 1 : 10 and a fiber loaded catalysis dosage of 40 mg. The liquid phase yield can reach 98% in 30 minutes and can be reused after washing with ethanol. Moreover, the composite material exhibited a good stability up to 10 cycles without a significant loss of its catalytic activity. The results show that the catalyst is easy to recover from the reaction system and has maintained good stability and catalytic activity after many cycles.

Via the help of polydopamine, polyacrylonitrile fiber catalysts functionalized with silver nanoparticles were prepared and employed for the reduction reaction of 4-nitrophenol to 4-aminophenol, with a yield of 98% in 30 minutes, and can be reused for up to 10 cycles.     

Biosynthesis of Ag–Pd bimetallic alloy nanoparticles through hydrolysis of cellulose triggered by silver sulfate

We report a simple but efficient biological route based on the hydrolysis of cellulose to synthesize Ag–Pd alloy nanoparticles (NPs) under hydrothermal conditions. X-ray powder diffraction, ultraviolet-visible spectroscopy and scanning transmission electron microscopy-energy dispersive X-ray analyses were used to study and demonstrate the alloy nature. The microscopy results showed that well-defined Ag–Pd alloy NPs of about 59.7 nm in size can be biosynthesized at 200 °C for 10 h. Fourier transform infrared spectroscopy indicated that, triggered by silver sulfate, cellulose was hydrolyzed into saccharides or aldehydes, which served as both reductants and stabilizers, and accounted for the formation of the well-defined Ag–Pd NPs. Moreover, the as-synthesized Ag–Pd nanoalloy showed high activity in the catalytic reduction of 4-nitrophenol by NaBH₄.

We report a simple but efficient biological route based on the hydrolysis of cellulose to synthesize Ag–Pd alloy nanoparticles (NPs) under hydrothermal conditions.     

Facile fabrication of multifunctional fabrics: use of copper and silver nanoparticles for antibacterial,superhydrophobic, conductive fabrics

This study aims to develop a multifunctional fabric for antibacterial, superhydrophobic and conductive performance using a facile fabrication method. Conductive metal particles, copper and silver, were used as antibacterial agents as well as a means to create nanoscale roughness on the fabric surface. Subsequent hydrophobic coating with 1-dodecanethiol produced a superhydrophobic surface. The single metal treatment with Cu or Ag, and the combined metal treatment of Cu/Ag were compared for the multifunctionality. The Cu/Ag treated fabric and the Cu treated fabric showed a bacteriostatic rate ≥ 99% and a sterilization rate ≥ 99% against S. aureus, suggesting a higher antibacterial activity against the Gram-positive bacteria. In contrast, the Ag treated fabric showed a lower antibacterial effect regardless of the bacteria type. With regards to conductivity, the single metal treated fabric did not exhibit conductivity; however the Cu/Ag treated fabric showed a high level conductivity with a surface resistivity of 25.17 ± 8.18 Ω sq⁻¹ and 184.38 ± 85.42 Ω sq⁻¹ before and after hydrophobic coating, respectively. Fabrics treated with Cu and Cu/Ag particles (with hydrophobic coating) displayed superhydrophobic characteristics with the contact angle of 161–162° and the shedding angle of 7.0–7.8°. The air permeability decreased after the particle treatment as the particles blocked the pores in the fabric. However, the water vapor permeability and tensile strength were not significantly affected by the particle treatment. This study is significant in that a multifunctionality of antibacterial effect, superhydrophobicity, and conductivity was achieved through the facile processes for metal nanoparticle attachment and hydrophobic coating. The multifunctional fabrics produced in this study can be practically applied to self-cleaning smart clothing, which has reduced laundering need, without hygiene concerns.

This study aims to develop a multifunctional fabric for antibacterial, superhydrophobic and conductive performance using a facile fabrication method.     

Silane coatings modified with hydroxyapatite nanoparticles to enhance the biocompatibility and corrosion resistance of a magnesium alloy

The fast corrosion rate of magnesium alloys has restricted their use as biodegradable implants. Hence developing a practical approach to retard the corrosion rate of the AZ31 magnesium alloy, as well as promoting cell adhesion and proliferation is of great importance. Silane coatings were applied through dip coating, on samples pretreated in hydrofluoric acid. Samples were immersed in simulated body fluid at 37 °C, and the coating performance was assessed by electrochemical impedance spectroscopy. The coating morphologies of samples were investigated through field emission scanning electron microscopy and a cell viability/proliferation (MTT) test was performed to evaluate cellular response. A 2.2 μm-thick coating was accomplished, which increased the corrosion resistance to three orders of magnitude higher than that of the bare sample. Hydroxyapatite nanoparticles were added to the silane coating to improve biocompatibility and facilitate bone formation. Changing the concentration of hydroxyapatite nanoparticles not only helped to optimize the barrier properties of the silane coating but also ameliorated MG-63 osteoblastic cell growth. The findings showed great promise to enhance and maintain the corrosion barrier property and induce high osteoblastic differentiation by employing 1000 mg L⁻¹ of hydroxyapatite nanoparticles.

Incorporation of hydroxyapatite nanoparticles in silane coatings improves both corrosion resistance and cell viability on magnesium AZ31 implants.     

Enhanced osteogenesis of mesenchymal stem cells on electrospun cellulose nanocrystals/poly(ε-caprolactone) nanofibers on graphene oxide substrates

Cellulose nanocrystals (CNCs) have received a great amount of attention to the production of micro/nano-platforms for tissue engineering applications. CNCs were extracted from rice husk biomass and characterized by different spectroscopic techniques. The biocompatibility of the extracted CNCs was revealed by the WST-1 assay technique in the presence of human mesenchymal stem cells (hMSCs) after different time intervals. An improvement in the mechanical properties was observed in the fabricated scaffolds (PCL/CNC) compared to PCL scaffolds. Graphene oxide (GO)-coated (PCL/CNC) electrospun scaffolds (GPC) were prepared by the deposition of PCL/CNC composite nanofibers on the surface of GO for tissue engineering. Notably, better cell proliferation and differentiation were observed in the presence of the fabricated scaffolds. This enhancement of the properties of the fabricated scaffolds was due to the presence of conductive GO moieties which facilitated the cellular response. Therefore, the fabricated materials have the potential to be used as a biomaterial for enhanced cell proliferation and osteogenic differentiation.

Cellulose nanocrystals (CNCs) have received a great amount of attention to the production of micro/nano-platforms for tissue engineering applications.     

A facile technique to prepare biodegradable coaxial electrospun nanofibers for controlled release of bioactive agents.

A one-step, mild procedure based on coaxial electrospinning was developed for incorporation and controlled release of two model proteins, BSA and lysozyme, from biodegradable core-shell nanofibers with PCL as shell and protein-containing PEG as core. The thickness of the core and shell could be adjusted by the feed rate of the inner dope, which in turn affected the release profiles of the incorporated proteins. It was revealed that the released lysozyme maintained its structure and bioactivity. The current method may find wide applications for controlled release of proteins and tissue engineering.     

Prevalence and properties of the intestinal alkaline phosphatase identified in serum by cellulose acetate electrophoresis.

We investigated the prevalence and characteristics of intestinal alkaline phosphatase (ALP; EC 3.1.3.1) identified in human serum by cellulose acetate electrophoresis in 8% of fasting serum samples from hospital patients (n = 500) and in 35% of fasting serum samples from patients with diabetes mellitus (n = 106; not differentiated between types 1 and 2). The intestinal ALP electrophoretic band was usually heterogeneous and contained two major subtypes of ALP. Isoelectric focusing of intestinal-ALP-positive serum treated with levamisole and neuraminidase (EC 3.2.1.18) revealed two distinct regions of enzymatic activity that comigrated with ALP extracted from small intestinal and colonic mucosa. Anodic intestinal ALP was resistant to treatment with levamisole and neuraminidase and comigrated with ALP from small intestinal mucosa. The more-cathodic intestinal ALP, which comigrated with ALP from colonic mucosa, was completely inhibited by levamisole and converted by neuraminidase to a species with a more basic pI than that of neuraminidase-digested tissue-nonspecific form. This component of intestinal ALP may be of vascular origin.