Simultaneous Crosslinking Research Articles

The Effect of Ti-6Al-4V Alloy Surface Structure on the Adhesion and Morphology of Unidirectional Freeze-Coated Gelatin

The modification of a metal implant surface with a biomimetic coating of bone-like anisotropic and graded porosity structures to improve its biological anchorage with the surrounding bone tissue at implanting, is still a high challenge. In this paper, we present an innovative way of a gelatin (GEL) dip-coating on Ti-6Al-4V substrates of different square-net surface textures by the unidirectional deep-freezing process at simultaneous cross-linking using carbodiimide chemistry. Different concentrations of GEL solution were used to study the changes in morphology, density, and mechanical properties of the coatings. In addition, the surface free energy and polarity of Ti-6Al-4V substrate surfaces and GEL solutions have been evaluated to assess the wetting properties at the substrate interfaces, and to describe the adhesion of GEL macromolecules with their surfaces, being supported by mechanical pull-out testing. The results indicate that the coating’s morphology depends primarily on the Ti-6Al-4V substrate’s surface texture and second, on the concentration of GEL, which further influences their adhesion properties, orientation, morphological arrangement, as well as compression strength. The substrate with a 300 × 300 μm2 texture resulted in a highly adhered GEL coating with ≥80% porosity, interconnected and well-aligned pores of 75–200 μm, required to stimulate the bone ingrowth, mechanically and histologically.

Disposable Micropipette Tip for Purifying DNA Fragments

A novel functional micropipette tip for DNA purification, called DNAtip, is described based on a novel coating process. The functional layer is prepared by an internal coating with silica particles supported into a polyvinyl alcohol (PVA) film. The coating layer is stabilized by simultaneous radiation-induced crosslinking to avoid its dissolution. Three types of silica particles of different diameters: micron, sub-micron, and nano sizes are studied. In addition, pH of the coating solution and concentration of the silica particles were optimized. Tips coated with fumed silica showed the highest absorption capacity of a plasmid DNA with an acceptable purity. Different linear dsDNA fragments were used for evaluating the absorption capacity and size discrimination of fragments. The recovery in the range of 700 ng and 200 ng per tip was measured for dsDNA fragments in the range of 400 bp to 2 kbp and 50 bp to 500 bp respectively. DNA PCR fragments contaminated with BSA were successfully purified with sufficient quality to be sequenced or enzymatically digested. This disposable tip device, useful for plasmids or DNA fragments purification, is a novel lab-on-a-tip device, which can effectively improve automate genetic engineering procedures.

Core-Cross-Linked Micelles Made by RAFT Polymerization with a Polycationic Outer Shell Based on Poly(1-methyl-4-vinylpyridinium)

A convergent synthesis of amphiphilic polymers with a polystyrene (PS) core and a polyelectrolytic poly(1-methyl-4-vinylpyridinium iodide) (P4VPMe+I–) shell is reported. The polymers were obtained by reversible addition–fragmentation chain transfer (RAFT) polymerization in water using a trithiocarbonate chain transfer agent [R0-SC(S)SPr, R0 = −C(Me)(CN)CH2CH2COOH]. Two types of particle structure, both having a spherical morphology and diameters in the 85–150 nm range, have been obtained as stable latexes with polymer content up to 10% in weight. The first structure consists of core-cross-linked micelles (CCMs), where amphiphilic P4VPMe+I–-b-PS arms are cross-linked at the hydrophobic end by the use of diethylene glycol dimethacrylate. The Coulombic repulsion between the outer shells of the precursor micelles ensures the absence of macrogelation during the cross-linking step. The second structure consists of nanogels (NGs), where the entire hydrophobic core is cross-linked during the last step of simultaneous chain extension and cross-linking of a P4VPMe+I–-b-PS intermediate with a short PS block. The lack of radical polymerization for the 4VPMe+I– monomer and the lack of chain extension with styrene for a R0-P4VPMe+I–-SC(S)SPr intermediate were circumvented by the synthesis of R0-P4VP-b-PS-SC(S)SPr containing a short PS block by sequential RAFT polymerization of 4-vinylpyridine (4VP) and styrene, followed by quantitative cationization of the P4VP block by MeI and subsequent sequential (for the CCMs) or simultaneous (for the NGs) chain extension and cross-linking.

Glucose oxidation by enzyme electrodes using genipin to crosslink chitosan, glucose oxidase and amine-containing osmium redox complexes

Genipin is used to simultaneously crosslink chitosan, amine-containing osmium redox complex and glucose oxidase on graphite disks to produce enzyme-based electrodes for glucose oxidation. The enzyme electrodes produce glucose oxidation current densities of 730 µA cm−2 in 50 mM phosphate buffered saline (150 mM NaCl, pH 7.4, 37 °C) containing 100 mM glucose at an applied potential of 0.45 V (vs. Ag/AgCl), higher than the 440 µA cm−2 for conventional poly(ethylene glycol) diglycidyl ether (PEGDGE) epoxy ring-opening cross-linked films. Addition of multiwalled carbon nanotubes results in current response as high as 4.9 ± 0.3 mA cm−2 in 100 mM glucose. The genipin cross-linked hydrogels deliver a 3 fold increase in stability for continuous amperometric current production over a 20 h period when compared to PEGDGE cross-linked hydrogels. Genipin provides an effective route for simultaneous crosslinking glucose oxidase, chitosan and the redox complex while further optimisation of the crosslinking process holds promise for application of the enzyme electrodes as fuel cell and sensor devices.

Yarn-reinforced hydrogel composite produced from woven fabrics by simultaneous dissolution and cross-linking

Polyvinyl alcohol (PVA)/cotton (Co) woven fabrics were produced by constructing Co as warp yarns and PVA as weft yarns in the fabric structure. As-prepared PVA/Co fabrics were treated with borax/water solution. Because of the simultaneous dissolution and gelation of PVA yarn in the fabric and transformation of PVA molecules into cross-linked gel structures, gel penetrated among the yarns in the matrix form and hence Co yarn-reinforced composite hydrogels were obtained. The retention time of water by composite hydrogels was first increased and then decreased by increasing borax concentration in the cross-linker solution. With yarn reinforcing, the tensile strength of hydrogel structure significantly increased. Mechanical properties of hydrogel composites were very variable depending on water content in the structure and tensile strength tremendously increased when water evaporated from the structure. Thermal and chemical characterizations of yarn-reinforced hydrogel composites were conducted in addition to swelling and mechanical analysis to investigate the performance of the hydrogel composites.

Simultaneous hydrogel crosslinking and silver nanoparticle formation by using ionizing radiation to obtain antimicrobial hydrogels

Hydrogel dressings are crosslinked hydrophilic polymers able of swelling in presence of water and can be used in many different types of wound care. In turn, in wound care, silver has been used for a long time as an effective antimicrobial agent. Recent studies have demonstrated an increase of its antimicrobial action when it is used at nanometer scale, that is, as silver nanoparticles (AgNPs), which have anti-inflammatory effect on infected wounds, rashes, and mesh skin grafts. The objective of this work was to study hydrogel dressings containing AgNPs from silver nitrate, synthesized by radiation involving the formation of silver nanoparticles with simultaneous occurrence of crosslinking and sterilization of the polymer systems. One of the hydrogels was prepared with poly(N-vinyl-2- pyrrolidone) (PVP) and the other with poly(vinyl alcohol) (PVA) as main studied polymers. An aqueous solution of AgNO3 was added to both polymer systems separately. The AgNPs synthesis, polymer crosslinking and dressing sterilization were achieved simultaneously by irradiating the resultant solutions with gamma-rays from a 60Co source. Gel fraction, swelling in reverse osmosis water, SEM-EDS, UV-visible spectroscopy, and antimicrobial activity were performed and characterized. The obtained results showed that the dressings have a soft consistency, high degree of crosslinking and swelling, homogeneous distribution of AgNPs with peaks of plasmonic bands about 400 nm, but only PVP hydrogel showed antimicrobial properties to P. aeruginosa and normal S. aureus. Moreover, this hydrogel also showed antimicrobial properties to S. aureus strain multiresistant to penicillins, cephalosporins, carbapenems, sulfonamides, tetracyclines, quinolones, and aminoglycosides, whereas the PVA hydrogel showed antimicrobial properties to P. aeruginosa and bacteriostatic activity to S. aureus. The results suggest that both synthesized dressings have potential for use in wounds and burns infected with gram-positive and gram-negative bacteria.

Preparation and optimization of thorium selective ion imprinted nonwoven fabric grafted with poly(2-dimethylaminoethyl methacrylate) by electron beam irradiation technique

2-dimethylaminoethyl methacrylate (DMAEMA) was grafted onto PP/PE non-woven fabrics (NWF) using pre-radiation graft polymerization technique and subsequent mutual radiation crosslinking with divinylbenzene (DVB). The ion-imprinted polymer (IIP) was synthesized by DVB crosslinking with DMAEMA and thorium complex through radiation. Non-imprinted polymer (NIP) was prepared with the same conditions but utilizing pure DMAEMA instead of DMAEMA-Thorium complex. The NWF, DMAEMA-grafted-NWF, IIP and NIP were characterized with Field Emission Scanning Electron Microscopy (FESEM), Fourier Transformed Infrared Spectroscopy (ATR-FTIR), Thermogravimetric Analyzer (TGA), X-ray photoelectron spectroscopy (XPS), and X-ray Diffraction (XRD). The grafting process parameters were optimized prior to radiation crosslinking with DVB. The effects of DMAEMA concentration and reaction temperature as a function of different irradiation doses were investigated in order to attain optimal grafting conditions. The effects of DVB concentration, process temperature and radiation dosage on the degree of crosslinking were examined. In addition, the effects of crosslinking percentage, initial thorium concentration and concentration of imprinted thorium to the selectivity of IIP and NIP were also determined. The thorium selectivity of both IIP and NIP was measured using batch mixed ions system by inductively coupled plasma mass spectrometry (ICP-MS) analysis. Instead of simultaneous grafting and crosslinking process in bulk along with imprint template, this current study conciliates all grafting, imprint template and crosslinking process independently. Thus, the originality of the research is attributed to individuality grafting and crosslinking technique using ion beam irradiation to obtain IIP of high thorium selectivity without compromising the chemical and physical properties of the adsorbent.

A Millifluidic Device with Embedded Cross-Linked Enzyme Aggregates for Degradation of H2O2.

Millifluidic devices decorated with enzymes have been used for enzymatic reactions in continuous processes, but low enzymatic activity and enzyme leaching remain as challenges. Herein, we develop a strategy to embed cross-linked enzyme aggregates (CLEAs) on the surfaces of millifluidic devices to achieve higher enzymatic activity and better stability. Catalase was chosen as a model enzyme to degrade H2O2 in wastewater samples. First, CLEA of catalase (153 ± 10 nm) was formed by simultaneous precipitation and cross-linking with 25.0 wt % acetonitrile containing 0.025 wt % glutaraldehyde in a millifluidic device. To immobilize CLEA, we first swell a piece of plastic tubing by using 5.0 wt % acetonitrile and then immerse it in an aqueous solution with 5.0 wt % (3-aminopropyl)triethoxysilane (APTES) and 5.0 wt % dextran polyaldehyde (DPA) subsequently. After CLEA is absorbed inside the expanded polymer network of the tubing, the tubing is tightened by using a vacuum to secure the immobilized CLEA. The millifluidic device decorated with CLEA of catalase has total activity of 660 U for degradation of H2O2, and it shows good stability under a flow rate of 200 μL/min. The tubing can be used to degrade 0.1 wt % H2O2 solution continuously for 3 h or remove 2 wt % residual H2O2 in wastewater for 2 h. The technique is general enough and can be applied to other types of enzymes for continuous enzymatic reactions.

Simultaneous intramolecular crosslinking and sterilization of papain nanoparticles by gamma radiation

Papain-based nanoparticles were recently developed using radiation technologies and proven effective to generate nanosized crosslinked papain particles with preserved enzymatic activity. The applications of such nanostructured systems are expected to be similar to native papain with considerable biopharmaceutical advantages and concern drug loading among other biotechnological applications. The nature of such crosslinks and the possibility to provide simultaneous sterilization have been hypothesized but remain not totally clarified. This manuscript advances the discussion on the radiation-induced synthesis of protein nanoparticles by approaching the nature of the crosslinking and the possible contribution of bityrosine linkages and disulfide bridges to the overall nanoparticle assembly as well as the feasibility of the simultaneous sterilization process under the pre-established conditions of processing. Papain nanoparticles were synthesized and characterized according to size, proteolytic activity, bityrosine, cysteine content and molecular weight by SDS-PAGE upon sonication at 40 kHz. Bacterial identification and the sterility tests were performed in accordance with ISO 11737 prior to and after inoculating 106 CFU of Corynebacterium xerosis. Our experiments evidenced the crosslinking of rather intra- than intermolecular nature and a contribution of cysteine bridges and bityrosine linkages to the stabilization and formation of the papain nanoparticle assembly. The technique was effective to promote simultaneous crosslinking and sterilization at the established conditions of processing and may be validated in accordance with the ISO 11137.

Refractive surgery with simultaneous collagen cross-linking for borderline corneas - A review of different techniques, their protocols and clinical outcomes.

Simultaneous corneal cross-linking (CXL) has been proposed as an adjunct therapy to corneal refractive procedures to prevent future ectasia, especially when performed in borderline corneas. This review analyses the currently available literature (minimum follow-up 6 months) on corneal refractive surgery and simultaneous CXL (PRK Xtra, LASIK Xtra, and SMILE Xtra) to evaluate the overall results including the safety, efficacy, and potential complications associated with these procedures. A comprehensive literature search of various electronic databases (PubMed, PubMed Central, Cochrane database, and MEDLINE) was performed up to 20th May 2020. Four relevant studies were found for PRK Xtra, 12 for LASIK Xtra, and 3 for SMILE Xtra. The total number of eyes included in this review was 1,512: 294 for PRK Xtra, 221 for PRK-only, 446 eyes for LASIK Xtra, 398 eyes for LASIK-only, 91 for SMILE Xtra and 62 for SMILE-only. Current literature suggests that refractive surgery and simultaneous CXL is generally safe and delivers comparable results in terms of visual and refractive outcomes than refractive surgery alone. However, there is no consensus on a standard cross-linking protocol, and complications such as diffuse lamellar keratitis, central toxic keratopathy, and corneal ectasia following Xtra procedures have been reported. It is therefore suggested that surgeons exercise caution in case-selection and counsel their patients regarding the potential risks and benefits with Xtra procedures. Also, further studies are required to standardize the UV-A irradiation protocols and to evaluate the long-term effect on safety, refractive predictability, and stability of these procedures.

Fabrication of dual catalytic microcapsules by mesoporous graphitic carbon nitride (mpg-C3N4) nanoparticle–enzyme conjugate stabilized emulsions

Dual catalytic microcapsules (MCs) were fabricated by simultaneous self-assembly and cross-linking of mpg-C3N4 nanoparticles (NPs) and lipase conjugates at oil–water interface.

One-step synthesis of poly(ethylene oxide)/gold nanocomposite hydrogels and suspensions using gamma-irradiation

Poly(ethylene oxide) (PEO)/gold nanocomposite hydrogels and suspensions were synthesized by γ-irradiation of PEO and Au3+ aqueous solutions to a dose of 50 kGy under inert atmosphere and without addition of 2-propanol, depending on the initial concentration of Au3+ and pH of solutions. The pH of the initial solutions had the major influence on the formation of PEO/Au nanocomposite hydrogels vs. suspensions. The pH and Au3+ initial concentration determined the AuNPs size and suspension stability, as determined by UV-Vis spectroscopy. The neutral pH favored the formation of stable suspensions with the smallest gold nanoparticles (AuNPs), whereas unstable suspensions and bigger nanoparticles (NPs) were obtained at acidic pH and by increasing Au3+ initial concentration. On irradiation at alkaline conditions PEO/AuNPs hydrogels were produced in one-pot synthesis method - by simultaneous crosslinking of PEO chains and reduction/synthesis of Au nanoparticles. Scanning electron microscopy of nanocomposite gels revealed the gold nanoparticles embedded in PEO matrix with homogenous distribution. The thermal and viscoelastic properties of PEO/AuNPs gels depended on the initial Au3+ concentration, that is on amount of AuNPs synthesized inside gels. Lower particle content resulted in gels with generally higher melting and crystallization temperatures as well as higher storage moduli, yield points and flow points than pure PEO gel. The optimal amount were up to 1 wt% Au for obtaining stronger gels, whereas higher amount of NPs, because of NPs agglomeration, lead to deterioration of gel properties and significant weakening of gel.

New Class of Crosslinker-Free Nanofiber Biomaterials from Hydra Nematocyst Proteins

Nematocysts, the stinging organelles of cnidarians, have remarkable mechanical properties. Hydra nematocyst capsules undergo volume changes of 50% during their explosive exocytosis and withstand osmotic pressures of beyond 100 bar. Recently, two novel protein components building up the nematocyst capsule wall in Hydra were identified. The cnidarian proline-rich protein 1 (CPP-1) characterized by a “rigid” polyproline motif and the elastic Cnidoin possessing a silk-like domain were shown to be part of the capsule structure via short cysteine-rich domains that spontaneously crosslink the proteins via disulfide bonds. In this study, recombinant Cnidoin and CPP-1 are expressed in E. coli and the elastic modulus of spontaneously crosslinked bulk proteins is compared with that of isolated nematocysts. For the fabrication of uniform protein nanofibers by electrospinning, the preparative conditions are systematically optimized. Both fibers remain stable even after rigorous washing and immersion into bulk water owing to the simultaneous crosslinking of cysteine-rich domains. This makes our nanofibers clearly different from other protein nanofibers that are not stable without chemical crosslinkers. Following the quantitative assessment of mechanical properties, the potential of Cnidoin and CPP-1 nanofibers is examined towards the maintenance of human mesenchymal stem cells.

A Novel Double‐Crosslinking‐Double‐Network Design for Injectable Hydrogels with Enhanced Tissue Adhesion and Antibacterial Capability for Wound Treatment

AbstractMost photocrosslinkable hydrogels have inadequacy in either mechanical performance or biodegradability. This issue is addressed by adopting a novel hydrogel design by introducing two different chitosan chains (catechol‐modified methacryloyl chitosan, CMC; methacryloyl chitosan, MC) via the simultaneous crosslinking of carbon–carbon double bonds and catechol‐Fe3+ chelation. This leads to an interpenetrating network of two chitosan chains with high crosslinking‐network density, which enhances mechanical performance including high compressive modulus and high ductility. The chitosan polymers not only endow the hydrogels with good biodegradability and biocompatibility, they also offer intrinsic antibacterial capability. The quinone groups formed by Fe3+ oxidation and protonated amino groups of chitosan polymer further enhance antibacterial property of the hydrogels. Serving as one of the two types of crosslinking mechanisms, the catechol‐Fe3+ chelation can covalently link with amino, thiol, and imidazole groups, which substantially enhance the hydrogel's adhesion to biological tissues. The hydrogel's adhesion to porcine skin shows a lap shear strength of 18.1 kPa, which is 6‐time that of the clinically established Fibrin Glue's adhesion. The hydrogel also has a good hemostatic performance due to the superior tissue adhesion as demonstrated with a hemorrhaging liver model. Furthermore, the hydrogel can remarkably promote healing of bacteria‐infected wound.

Superelastic Multifunctional Aminosilane-Crosslinked Graphene Aerogels for High Thermal Insulation, Three-Component Separation, and Strain/Pressure-Sensing Arrays.

Aerogels have attracted great interest for their unique properties, but their mechanical brittleness and poor functionality highly limit their practical applications. Herein, we report unprecedented superelastic multifunctional aminosilane-crosslinked reduced graphene oxide (AC-rGO) aerogels that are prepared via a facile and scalable strategy involving simultaneous crosslinking and reducing of graphene oxide nanosheets with different kinds of aminosilanes via C-N coupling and hydrolytic polycondensation reactions. It is found that 3-aminopropyl(diethoxy)methylsilane (APDEMS) is the better choice to enhance hydrophobicity, elasticity, and other properties of the resulting aerogels compared with (3-aminopropyl)triethoxysilane. One APDEMS molecule plays three roles as a crosslinker, a reductant, and a hydrophobizing agent. An outstanding combination of high surface area, ultralow density, superhydrophobicity, supercompressibility, superelasticity, low thermal conductivity, ultrahigh absorption capacity for organic liquids, efficient three-component separation, and strain/pressure sensing has been achieved in a single APDEMS-crosslinked rGO aerogel for the first time. In addition, a flexible, highly sensitive, and moisture-resistant AC-rGO aerogel-based strain/pressure-sensing array for the effective detection of strain (0-80%)/pressure (10 Pa to 10 kPa) distributions and object shapes has been demonstrated.

Topometric Indices And Corneal Densitometry Change After Corneal Refractive Surgery Combined With Simultaneous Collagen Crosslinking.

PurposeTo show the alteration of tomography, topometric indices and corneal densitometry after corneal refractive surgery combined with collagen crosslinking.Patients and methodsAll medical records of patients undergoing corneal refractive surgery with simultaneous collagen crosslinking during April 2015 and August 2018 were retrospectively reviewed. Corneal tomography, higher-order aberrations (HOA), topographic indices and corneal densitometry were evaluated. All the data at 1 month, 3 months and 6 months were compared to baseline value. All complications were noted. P value less than 0.05 was considered statistically significant.ResultsMedical records of fourteen patients (twenty-five eyes) were reviewed. HOA increased at all time points (p < 0.05). Keratoconus index and central keratoconus index decreased, whereas index of surface variance, index of vertical asymmetry, index of height decentration and the minimum of radius of curvature increased at all time points (p < 0.05). Index of height asymmetry increased at 3 and 6 months (p < 0.05). Corneal densitometry at anterior layer of 0–10 mm zone and center layer of 0–6 mm zone increased at 1 and 3 months (p < 0.05). At 6 months, the densitometry at 0–6 mm zone returned to baseline level. However, at 6 months, at anterior and center layer of 6–10 mm zone, the densitometry values were still more than preoperative values (p < 0.05). There was one case of bacterial keratitis.ConclusionAfter the corneal refractive surgery combined with collagen crosslinking, the HOA and corneal densitometry increased. Topographic indices showed conflicting results.

Crosslinked Quaternized Poly(arylene ether benzonitrile) Membranes for Vanadium Redox Flow Batteries

Development of membrane separators is important to decrease cross-over and enhance efficiency and durability of non-aqueous redox flow batteries. Desired properties of the membranes for the application include (a) selective ion permeability, (b) high conductivity and (c) good chemical and mechanical stability in operating conditions of redox flow batteries. Our approach to satisfy these criteria is synthesizing cation-functionalized nitrile-containing polyaromatics, poly(arylene ether benzonitrile)s, for membrane separators. While these membranes exhibited good performances in an aqueous vanadium redox flow battery (VRFB) system, in non-aqueous systems where acetonitrile is used as electrolytes, the membranes could not be utilized due to their limited mechanical strength. To endure the harsh operating condition of non-aqueous VRFB, we developed crosslinked quaternized poly(arylene ether benzonitrile)s. A series of high molecular weight polymers with tertiary amine groups were synthesized via aromatic nucleophilic substitution polycondensation followed by the simultaneous quaternization and crosslinking reactions. In this presentation we will discuss the membrane properties and the electrochemical performance of these membranes in terms of cycling efficiencies, vanadium permeation and membrane durability. The applicability of crosslinked quaternized poly(arylene ether benzonitrile) membranes in non-aqueous VRFB systems will be summarized. Acknowledgement This work is fully supported by Laboratory Directed Research & Development, Los Alamos National Laboratory. The submission of the manuscript is approved by LANL (LA-UR-19-23557)

Modified crosslinking in the treatment of purulent keratitis and corneal ulcers

To evaluate the efficacy of modified crosslinking (M-CXL) in the treatment of purulent corneal ulcers, including those of mixed etiology. The M-CXL method consists of simultaneous cross-linking and frequent instillations (FI) of anti-infective solutions. We observed 36 patients (37 eyes) with purulent corneal ulcers (PCU) of various etiologies. The test group included 24 patients (24 eyes) who received 1–2 sessions of M-CXL with active conservative therapy. In the control group (12 patients, 13 eyes), only active conservative therapy was performed. Complete reduction of the purulent process was achieved in 18 (75%) eyes in 29.6 ± 9.38 days in the test group; and in 8 eyes (61.5%) in 50.4 ± 15.9 days in the control group. The efficiency of M-CXL ranged from 100% to 66.6% depending on depth and width (square area) of the infiltration in question. In cases where infiltration affected the entire stromal thickness, the M-CXL efficacy sharply decreased to 66.6%, even with its small (<6 mm) area. In cases where infiltrations extended to the Descemet’s membrane with an overall area >7 mm, the clinical effect of M-CXL was absent or insufficient. In 75% cases, M-CXL showed complete reduction of PCU. Comparing with control groups, the duration of treatment in the test group decreased 42% (P less than 0.05). In infiltrations over a wide area affecting all the layers up to the Descemet’s membrane, resorbtion of the purulent focus was not achieved. However, it’s spread and purulent fusion were sufficiently suspended, thereby allowing therapeutic penetrating keratoplasty to be performed with a smaller graft diameter.

Simultaneous hydrogel crosslinking and silver nanoparticle formation by using ionizing radiation to obtain antimicrobial hydrogels

Hydrogel dressings are crosslinked hydrophilic polymers able of swelling in presence of water and can be used in many different types of wound care. In turn, in wound care, silver has been used for a long time as an effective antimicrobial agent. Recent studies have demonstrated an increase of its antimicrobial action when it is used at nanometer scale, that is, as silver nanoparticles (AgNPs), which have anti-inflammatory effect on infected wounds, rashes, and mesh skin grafts. The objective of this work was to study hydrogel dressings containing AgNPs from silver nitrate, synthesized by radiation involving the formation of silver nanoparticles with simultaneous occurrence of crosslinking and sterilization of the polymer systems. One of the hydrogels was prepared with poly(N-vinyl-2- pyrrolidone) (PVP) and the other with poly(vinyl alcohol) (PVA) as main studied polymers. An aqueous solution of AgNO3 was added to both polymer systems separately. The AgNPs synthesis, polymer crosslinking and dressing sterilization were achieved simultaneously by irradiating the resultant solutions with gamma-rays from a 60Co source. Gel fraction, swelling in reverse osmosis water, SEM-EDS, UV-visible spectroscopy, and antimicrobial activity were performed and characterized. The obtained results showed that the dressings have a soft consistency, high degree of crosslinking and swelling, homogeneous distribution of AgNPs with peaks of plasmonic bands about 400 nm, but only PVP hydrogel showed antimicrobial properties to P. aeruginosa and normal S. aureus. Moreover, this hydrogel also showed antimicrobial properties to S. aureus strain multiresistant to penicillins, cephalosporins, carbapenems, sulfonamides, tetracyclines, quinolones, and aminoglycosides, whereas the PVA hydrogel showed antimicrobial properties to P. aeruginosa and bacteriostatic activity to S. aureus. The results suggest that both synthesized dressings have potential for use in wounds and burns infected with gram-positive and gram-negative bacteria.

Development of Copolyamide-66/6 Cross-Linked Foams by a One-Step Reactive Extrusion Process

The simultaneous chemical cross-linking and foaming of aliphatic copolyamide by one-step reactive extrusion using a bifunctional trialkoxysilaneimidazoline additive is studied. The aim was to reach efficient melt strength enhancing the cell growth without coalescence. From liquid NMR analyses, the cross-linked foam synthesis was evidenced resulting from both imidazoline ring opening (further reacting with the polyamide carboxylic acid end-groups) and alkoxysilane hydrolysis–condensation reactions (leading to cross-linking reaction and ethanol formation). From these chemical modifications, ethanol concomitantly released lead to the expansion of the cross-linked copolyamide. From the knowledge of this chemical mechanism, various extruder and formulation parameters have been modified and their impact scrutinized to optimize the foam morphology. With our optimized conditions, it was possible to synthesize rigid foam with mean pore size mainly below 90 μm and a density around 0.36 kg·m–3 while reaching reasona...