Porogen Ratio Research Articles

Polycaprolactone Hybrid Scaffold Loaded With N,O-Carboxymethyl Chitosan/Aldehyde Hyaluronic Acid/Hydroxyapatite Hydrogel for Bone Regeneration.

Hydrogels have emerged as potential materials for bone grafting, thanks to their biocompatibility, biodegradation, and flexibility in filling irregular bone defects. In this study, we fabricated a novel NAH hydrogel system, composed of N,O-carboxymethyl chitosan (NOCC), aldehyde hyaluronic acid (AHA), and hydroxyapatite (HAp). To improve the mechanical strength of the fabricated hydrogel, a porous polycaprolactone (PCL) matrix was synthesized and used as a three-dimensional (3D) support template for NAH hydrogel loading, forming a novel PCL/NAH hybrid scaffold. A mixture of monosodium glutamate (M) and sucrose (S) at varied weight ratios (5M:5S, 7M:3S, and 9M:1S) was used for the fabrication of 3D PCL matrices. The morphology, interconnectivity, and water resistance of the porous PCL scaffolds were investigated for optimal hydrogel loading efficiency. The results demonstrated that PCL scaffolds with porogen ratios of 7M:3S and 9M:1S possessed better interconnectivity than 5M:5S ratio. The compressive strength of the PCL/NAH hybrid scaffolds with 9M:1S (561.6 ± 6.1 kPa) and 7M:3S (623.8 ± 6.8 kPa) ratios are similar to cancellous bone and all hybrid scaffolds were biocompatible. Rabbit models with tibial defects were implanted with the PCL/NAH scaffolds to assess the wound healing capability. The results suggest that the PCL/NAH hybrid scaffolds, specifically those with porogen ratio of 7M:3S, exhibit promising bone healing effects.

Synthesis and characterization of ammonium polymer for anion removal in aqueous solutions

In a one-step thermal process using 2-[(methacryloyloxy)ethyl]trimethylammonium chloride (META), an ammonium polymer was successfully obtained for the removal of anions (nitrates, nitrites, and phosphates) from aqueous solutions. Ethylene dimethacrylate (EDMA) was used as a cross-linking agent. The effect of cross-linking agent, porogen, and polymerization time on the structure and physical properties of the obtained polymer was examined (FTIR, SEM, BET, elemental analysis). The optimal conditions for META synthesis were a monomer to porogen ratio of 20:80, 75% functional monomer content and a 12-hour polymerization time.

Rational Design of Pore Parameters in Monodisperse Porous Poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) Particles Based on Response Surface Methodology.

Monodisperse porous poly(glycidyl methacrylate-co–ethylene glycol dimethacrylate) particles are widely applied in different fields, as their pore properties can be influenced and functionalization of the epoxy group is versatile. However, the adjustment of parameters which control morphology and pore properties such as pore volume, pore size and specific surface area is scarcely available. In this work, the effects of the process factors monomer:porogen ratio, GMA:EDMA ratio and composition of the porogen mixture on the response variables pore volume, pore size and specific surface area are investigated using a face centered central composite design. Non-linear effects of the process factors and second order interaction effects between them were identified. Despite the complex interplay of the process factors, targeted control of the pore properties was possible. For each response a response surface model was derived with high predictive power (all R2predicted > 0.85). All models were tested by four external validation experiments and their validity and predictive power was demonstrated.

Micro-gel thin film molecularly imprinted polymer coating for extraction of organophosphorus pesticides from water and beverage samples

Molecularly imprinted polymers (MIPs) have become an important class of materials for selective and efficient adsorption of target analytes. Despite versatility of MIPs for fabrication in numerous formats, these materials have been primarily reported as solid phase extraction packing materials. An effective thin film MIP prepared on stainless steel substrate is reported here for high throughput enrichment of organophosphorus pesticides (OPPs) from water and beverage samples followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. The key factors controlling performance as well as best practices for optimized fabrication of thin film MIPs are presented. A pseudo-phase diagram is introduced to evaluate and predict the effect of the ratio of porogen (solvent, 1-octanol) volume to relative crosslinker mass on the desired polymer features (i.e., porosity, surface area, capacity, and selectivity). At low porogen ratios, a macroporous polymer with insignificant selectivity is formed, whereas at high porogen ratios a micro-gel polymer with superior selectivity towards targets is obtained. The porosity and morphology determined with nitrogen adsorption and scanning electron microscopy were attributed to specific regions in the pseudo-phase diagram. Other factors influencing selectivity and stability of the polymer, such as type of the template and its ratios with monomer (methacrylic acid) and crosslinker (ethylene glycol dimethacrylate) were optimized. The prepared thin film MIPs were characterized using adsorption isotherms and adsorption kinetics, and evaluated for matrix effects (high humic acid content) and cross-reactivity in presence of other pesticides and pharmaceuticals. The optimized method provided limits of quantitation (LOQs) ranged from 0.002 to 0.02 ng mL−1 in water and from 0.095 to 0.48 ng g−1 in apple juice. Regarding inter-device variability (CV∼10% without normalization), excellent linearity (R2 > 0.99), satisfactory accuracies (90–110%) and precisions (<15%) were obtained.

Facile fabrication of micro-/nanostructured, superhydrophobic membranes with adjustable porosity by 3D printing.

Porous membranes with special wetting properties have attracted great interest due to their various functions and wide applications, including water filtration, selective oil/water separation and oil skimming. Special wetting properties such as superhydrophobicity can be achieved by controlling the surface chemistry as well as the surface topography of a substrate. Three-dimensional (3D) printing is a promising method for the fast and easy generation of various structures. The most common method for 3D printing of superhydrophobic materials is a two-step fabrication process: 3D printing of user-defined topographies, such as surface structures or bulk porosity, followed by a chemical post-processing with low-surface energy chemicals such as fluorinated silanes. Another common method is using a hydrophobic polymer ink to print intricate surface structures. However, the resolution of most common printers is not sufficient to produce nano-/microstructured textures, moreover, the resulting delicate surface micro- or nanostructures are very prone to abrasion. Herein, we report a simple approach for 3D printing of superhydrophobic micro-/nanoporous membranes in a single step, combining the required topography and chemistry. The bulk porosity of this material, which we term “Fluoropor”, makes it insensitive to abrasion. To achieve this, a photocurable fluorinated resin is mixed with a porogen mixture and 3D printed using a stereolithography (SLA) printing process. This way, micro-/nanoporous membranes with superhydrophobic properties with static contact angles of 164° are fabricated. The pore size of the membranes can be adjusted from 30 nm to 300 nm by only changing the porogen ratio in the mixture. We show the applicability of the printed membranes for oil/water separation and the formation of Salvinia layers which are of great interest for drag reduction in maritime transportation and fouling prevention.

Morphology optimization and assessment of the performance limits of high-porosity nanostructured polymer monolithic capillary columns for proteomics analysis

This study targets the synthesis of high external-porosity poly(styrene-co-divinylbenzene) monolithic support structures with macropore and globule sizes in the sub-micron range, aiming at the realization of high-speed and high-resolution gradient separations of intact proteins and peptides. The thermodynamic and kinetic aspects of the free-radical polymerization synthesis were adjusted by tuning the porogen to monomer ratio, the porogen ratio, the initiator content, and polymerization temperature. Next, column morphology was linked to eddy-dispersion and mobile-phase mass-transfer contributions and the chromatographic performance limits were benchmarked against conventional packed columns and silica monoliths. Polymer monolithic structures yielding a separation impedance as low as 976 were created allowing to generate N > 1,000,000 (for an unretained marker), albeit the expense of very long analysis times. Decreasing the macropore and globule sizes below a certain threshold led to significant increase in eddy dispersion, as globular entities agglomerate, and a small number of large flow-through pores permeate the overall fine interconnected polymer network with small diameter flow-through pores. The potential of monolith chromatography for proteomics application is demonstrated with a ballistic 6 s gradient separation of intact proteins and a high-resolution nanoLC-Orbitrap mass spectrometric analysis of a tryptic E. coli digest applying a coupled-column system.

Separation of histidine enantiomers by capillary electrochromatography with molecularly imprinted monolithic columns

AbstractIn this study, we aimed to separate the enantiomeric forms of d,l‐histidine, one of the essential amino acids, through molecular imprinted monolithic capillary electrochromatography columns prepared using hydrophobic N‐methacryloyl‐(l)‐phenylalanine methyl ester as the functional monomer, and l‐histidine as the template molecule. We investigated the effect of monomer ratio, temperature, template molecule mole ratio, crosslinker ratio, and porogen ratio to improve the permeability properties of the monolithic column. Characterization studies of the column were evaluated by attenuated total reflectance‐Fourier transform infrared spectroscopy, scanning electron microscopy, and Brunauer–Emmett–Teller analysis. The chromatographic performance of the column was investigated using alkylbenzene‐derived compounds. We evaluated some parameters to determine the optimum conditions for electrochromatographic studies such as electric field, organic solvent ratio, and pressure effect. The calculated imprinting factor (2.18) proved that the l‐histidine imprinted amino acid‐based monolithic column separated d,l‐histidine molecules efficiently (percent relative standard deviation &lt; 1.5) from each other using molecular imprinting technique with high‐resolution values (resolution value &gt; 1.5). As a result, selective d,l‐histidine separation was achieved in less than 10 min at pH 7.0 without using a ligand or extra modification step for the first time.

Electrochromatographic separation of hydrophobic amino acid enantiomers by molecularly imprinted capillary columns

In the present study, the enantiomeric forms of hydrophobic amino acids (l-tryptophan, l-tyrosine, and l-phenylalanine) were separated by molecularly imprinted capillary columns (MICC) via Capillary Electrochromatography (CEC) for the first time. The monomer ratio, crosslinker ratio, template molecule ratio, the porogen ratio and type, polymerization time, and also the effect of temperature were examined to increase the permeability properties of MICC. FTIR, SEM and BET analyses were realized for the characterization of MICC. The effect of the electric field, organic solvent ratio, and pressure were carried out experimentally to determine the optimum conditions. The separation performances of MICC and the non-imprinted capillary columns (NICC) were compared electrochromatographically.

A monolithic capillary modified with a copoplymer prepared from the ionic liquid 1-vinyl-3-octylimidazolium bromide and styrene for electrochromatography of alkylbenzenes, polycyclic aromatic hydrocarbons, proteins and amino acids.

A monolithic capillary column was prepared by single-step copolymerization of the ionic liquid 1-vinyl-3-octylimidazolium bromide (VOI) and styrene. The VOI and styrene monomers were introduced to provide multiple interaction sites and increase hydrophobicity and aromaticity of the monolithic column, respectively. The effect of porogen ratio, monomer ratio and reaction temperature on permeability was investigated. The resulting column was characterized by scanning electron microscopy, and the results suggest that the column possesses high porosity and good homogeneity. A relatively strong anodic electroosmotic flow was generated over a wide range of pH values (pH2.0-10.0), and this facilitates the rapid separation of analytes within 12min. Alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs), proteins and amino acids were used to evaluate the performance of the monolithic column under capillary electrochromatography mode by UV detection. Mixed-mode retention mechanisms including hydrophobic interaction, π-stacking, ion-exclusion interaction were observed. The monolithic column exhibits high column efficiency (8.72 × 104 plates∙m-1) and satisfying separation capability (the resolution of four alkylbenzenes: 2.54, 2.86 and 4.62, four PAHs: 2.79, 4.83 and 4.77, three proteins: 4.35 and 2.86, two amino acids: 3.34). Graphical abstractSchematic representation of capillary electrochromatography (CEC) systems with ionic liquid and styrene based organic polymer monolithic column for separation of alkylbenzenes, polycyclic aromatic hydrocarbons, proteins and amino acids.

Preparation of graphene oxide incorporated monolithic chip based on deep eutectic solvents for solid phase extraction

A monolithic chip incorporated with graphene oxide (GO) based on deep eutectic solvents (DESs) was developed for solid phase extraction (SPE). The carboxylated GO was modified with p-aminostyrene (pAS) by amidation, and the obtained GO (pAS–COOH–GO) was covalently incorporated into poly(butyl methacrylate-co-ethylene glycol dimethyl methacrylate) monolithic chip. Due to the high viscosity characteristics of DESs, a uniform pAS–COOH–GO incorporated monolithic chip with good permeability can be achieved. A systematic study of the preparation parameters on the performance of the resulting monolith was carried out, including the content of pAS–COOH–GO, DESs composition and porogen ratio. The resulting pAS–COOH–GO incorporated monolith was characterized by nitrogen adsorption, scanning electron microscopy, and transmission electron microscopy. The GO-doped monolithic chip can be used for SPE of polycyclic aromatic hydrocarbons (phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, benzo(a) pyrene, dibenzo(a,h)anthracene and inden(1,2,3,-cd)pyrene). The recoveries were all higher than 90%, which was about twice as high as that of the monolithic chip prepared without GO. By comparing the SPE results with that of GO free monolithic chip, good enrichment effects were demonstrated on the pAS–COOH–GO incorporated monolithic chip.

Pembuatan Kolom Monolit Mixed-Mode untuk Pemisahan Fenol dalam Kromatografi Cair Sistem Kapiler

A Mixed-Mode monolithic column prepared from Pentaeritrytol Tetraacrylate (PETRA) and Ethylene dimathacrylate (EDMA) was investigated and used in capillary liquid chromatography. The polymer composition was optimized by varying percentage ratio of monomer and porogens. Column A with rasio 35/65 (monomer/porogen) showed the optimum ratio. The polymerization of acrylic groups were conducted by in-situ preparation in capillary fused silica. Three phenol compounds were separated using this monolithic column using acetonitrile 100% as eluent. Monolith PETRA-EDMA also could work to separate polar and non-polar compound simultaneously by HILIC mode using acetonitrile 90% as eluent. The morphology surface of monolith was observed by scanning electron microscope (SEM) and mechanical stability in term of pressure drop was observed as well.

Enhanced molecular recognition for imprinted monolithic column containing polyhedral oligomeric silsesquioxanes by dendritic effect of mesoporous molecular sieve scaffolds.

The dendritic effect of nano mesoporous molecular sieve was first used to enhance molecular recognition of molecularly imprinted polymers (MIPs)-based polyhedral oligomeric silsesquioxanes (POSS). In this study, the MIPs were made using S-naproxen (S-NAP) as template molecule, 4-vinylpyridine (4-VP) as functional monomer, ethylene glycol dimethacrylate as cross-linker, 1-butyl-3-methylimidazoliumtetrafluoroborate ([BMIM]BF4)/DMSO as binary porogens, 1-propylmethacrylate-heptaisobutyl substituted as POSS monomer, and mesoporous molecular sieve (Mobil composition of matter No. 41, MCM-41) as dendritic scaffold. The influence of synthesis parameters on the imprinting effect, including the content of POSS monomer and derivatized MCM-41-MPS, the ratio of template to monomer, and the ratio of binary porogens were also investigated, respectively. The morphology of the polymers was characterized by scanning electron microscopy, nitrogen adsorption, and X-ray powder diffraction. The results showed that POSS&MCM-41-MPS MIP had a stronger imprinting effect with an imprinting factor 6.86, which is approximately 2.4, 2.3, and 3 times than that of POSS MIP, MCM-41-MPS MIP, and conventional MIP, respectively. The increase of affinity might be attributed to impediment of the chain motion of polymer due to improved POSS aggregation and the dipole interaction between the POSS units by introduce of MCM-41-MPS as scaffolds. The resulting POSS&MCM-41-MPS MIP was used as adsorbent for the enrichment of S-NAP in solid-phase extraction with a high recovery of 97.65% and the value of RSD was 0.94%.

Novel adamantane-based periodic mesoporous organosilica film with ultralow dielectric constant and high mechanical strength

In this work, a novel bridged organosilane precursor, adamantane-bridged organosilane (ADBO), was synthesized successfully which was employed to prepare adamantane-based (ADH-based) periodic mesoporous organosilica (PMO) thin film in the presence of porogen and acid catalyst via evaporation-induced self-assembly (EISA) after spin-coating procedure. The resultant ADH-based PMO thin films were characterized by FTIR, NMR, TEM, and small-angle XRD. The ADH-based PMO thin film with weight ratio of porogen to ADBO (0.75:1) possesses low dielectric constant (1.55 ± 0.04@1 MHz), excellent Young’s modulus (6.69 ± 0.54 GPa), and ideal hydrophobic property (90.2° of water contact angle) simultaneously. These outstanding properties of ADH-based PMO film can be ascribed to lower polarity, lower density, and rigid cavity structure of adamantane, which suggests its potential application as high-performance low-κ material in next-generation microelectronics.

One-pot preparation of an organic polymer monolith by thiol-ene click chemistry for capillary electrochromatography.

A novel organic monolith was successfully fabricated by a one-pot thiol-ene click reaction of triallyl isocyanurate with pentaerythritol tetrakis-(2-mercaptoacetate) and mercaptopropionic acid in the presence of porogens. We investigated the effects of the ratio of monomer and cross-linking agent, the type and ratio of porogen, and click reaction temperature on the permeability and morphology of the prepared poly triallyl isocyanurate-co-pentaerythritol tetrakis (2-mercaptoacetate) monoliths. The monolith was also characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The results indicated that the monoliths had continuous porous framework, good permeability, and high mechanical stability. A series of analytes with different properties such as alkylbenzenes, polycyclic aromatic hydrocarbons, anilines, and phenols were used to evaluate the electrochromatographic performance of the prepared monoliths in pressurized capillary electrochromatography. The prepared polymer monolith showed typical reversed-phase electrochromatographic behavior for hydrophobic substances. Moreover, the prepared monolith showed a mix of reversed-phase and cation exchange interaction modes for basic aniline compounds. The minimum plate height of the monolith was 8.76μm (132100 plates/m) for propylbenzene. These results demonstrated that one-pot thiol-ene click chemistry can provide a simple and reliable method for the preparation of organic monoliths.

聚醚砜(PES)多孔材料的制备与表征

选用二甲基乙酰胺(DMF)溶剂，将聚醚砜(PES)溶解，再与研磨处理的氯化钠(NaCl)致孔剂颗粒混合均匀，采用浇铸法制成PES/氯化钠(NaCl)材料。用去离子水抽提氯化钠形成PES多孔材料，研究PES的孔结构、孔隙率和吸水率等与成孔剂的关系。使用同一粒径致孔剂，得到的PES孔材料的吸水率随着致孔剂用量增大而增大，但是当PES与致孔剂超过一定质量比后，吸水率减小。使用三个不同粒径的致孔剂，PES孔材料的吸水率与孔结构尺寸没有线性关系。采用光学显微镜和扫描电镜对PES孔结构进行了表征，发现该材料是具有孔隙间连通的三维多孔材料。 Dimethylacetamide (DMF) was used as the solvent to dissolve the polymer, and then mixed with the treated sodium chloride (NaCl) porogen granules. The polymer/sodium chloride (NaCl) materials were prepared by casting method. The PES porous materials were extracted with deionized water to study the pore structure, porosity and water absorption of PES. Using the same particle size porogen, the water absorption of the PES pore material increases with the amount of porogen, but when the mass ratio of PES and porogen is more than a certain degree, the water absorption decreased. The water absorption of the PES pore material was not linearly related to the size of the pore structure using three porosens of different particle sizes. The PES pore structure was characterized by optical microscopy and scanning electron microscopy. It was found that the material was a three-dimensional porous material with inter-pore connectivity.

Porous Polymer Microneedles with Interconnecting Microchannels Toward Efficient Sensing of Interstitial Fluid

The microneedle array, the two-dimensional array of small needles of submillimeter length, is a minimally invasive alternative to conventional hypodermic needles. It penetrates skin and bypasses the diffusion barrier of stratum corneum and facilitates drug delivery as well as sampling and electrochemical sensing of biologically relevant molecules in interstitial fluid.1,2 Microneedles for sampling interstitial fluid fall into three types: hollow microneedles, hydrogel microneedles, and porous microneedles. Hollow microneedles have a bore inside the microneedle made by a photolithographic process. Hydrogel microneedles swell by absorption of interstitial fluid, and ex vivo analysis has been achieved. Porous microneedles have random pores in the body of the microneedle, and they have advantages such as a large pore volume ratio, efficient capillary action by many microchannels, large surface area for immobilization of sensor molecules, etc. Making porous microneedles with a polymer material has the advantages such as biocompatibility, easy fabrication by molding, a variety of molecular structures for tuning properties, etc. Despite their apparent advantages, the fabrication of porous polymer microneedles has been a challenge. In this study, we have fabricated microneedle arrays made of a porous polymer with interconnecting micropores.3 A porous polymer monolith is synthesized by polymerizing glycidyl methacrylate (GMA) with bi- and trifunctional crosslinkers by the irradiation of 365 nm UV in the presence of poly(ethylene glycol) in 2-methoxyethanol as a porogen, followed by washing with methanol/water.4 We fabricated a porous polymer monolith of this poly(glycidyl methacrylate) (PGMA) in a soft polydimethylsiloxane mold. The resulting microneedle array was a hard, opaque solid (Figure (a)), whereas a control with no porogen was transparent. Scanning electron microscopy (SEM) observation revealed that microneedles made with a porogen have interconnecting pores with ~1 µm in diameter on the surface and interior (Figure (b)). The porous microneedles with varied porogen ratios were fabricated to investigate its effects on porosity, water absorption speed, and skin penetration efficiency. Porosity was measured by weight increase of the porous microneedles after immersion into water. As an porogen ratio was increased, the porosity increased as well. The pore connectivity parameter, defined as (porosity)/(porogen ratio), versus a porogen ratio showed a sigmoidal profile that converges to unity, which indicated all the pores are interconnecting and accessible from the surface above a certain threshold of the porogen ratio. Water absorption speed of the porous microneedles was evaluated by a piece of water sensor paper that turns blue upon water absorption. The water sensor was attached on the top surface of the microneedle array, and the response time of the water sensor was measured. The response time decreased sharply to less than 20 minutes at the 36% porogen ratio, and this was consistent with the threshold of the porogen ratio for pore connectivity. The microneedle arrays were applied to a pig skin with the force of 1 N/needle, and punctured spots of the pig skin were stained with trypan blue. The microneedle arrays with lower porogen ratios had higher penetration efficiencies, and the porous microneedles with >80% penetration efficiency was achieved for the porogen ratio no more than 49%. With the lower porogen ratios, the porous microneedles become mechanically more robust, and the tips of the microneedles become sharper. In summary, by optimizing the porogen ratio (Figure (c)), we successfully developed porous polymer microneedles that combine fast water absorption speed and high skin penetration efficiency. The fabricated porous microneedles are a potentially versatile tool for sampling and sensing of interstitial fluid.

Ultra-low-κ HFPDB-based periodic mesoporous organosilica film with high mechanical strength for interlayer dielectric

A novel bridged organosilane precursor with star-shaped construction, [hexfluoropropane-2,2-diyl)dibenzyl-bridged organosilane (HFPDBO)], is prepared by facile organic synthesis method. The resultant HFPDBO precursor is mixed with porogen and acid catalyst to prepare periodic mesoporous organosilica (PMO) thin film via evaporation-induced self-assembly after spin-coating procedure. All the as-prepared HFPDB-based PMO thin film has been characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectrum, scanning electron microscopy, transmission electron microscope, and small-angle X-ray diffraction, respectively. Thereinto, the HFPDB-based PMO thin film with weight ratio of porogen to precursor (0.75:1) possesses excellent dielectric property (1.58@1 MHz of dielectric constants), high mechanical property (5.54 ± 0.11 GPa of Young’s modulus) and hydrophobic property (90.1° of water contact angle) simultaneously. These low dielectric constant, high mechanical strength, and the hydrophobicity suggest potential application of the HFPDB-based PMO thin films as low-k materials in microelectronics.

Polymer phase transition in n‐lauryl methacrylate monoliths

AbstractMonolithic materials prepared from a mixture of n‐lauryl methacrylate (LMA) and ethylene glycol dimethacrylate (EGDMA) dedicated to nano‐liquid chromatography separation were synthesized using in situ UV polymerization in 75 µm inner diameter capillary tubing. A mixture of cyclohexanol and ethylene glycol was used as a porogen to control porosity. While the preparation conditions yielded satisfactory analytical results, values of pertinent parameters turned out to be critical for obtaining columns with efficient separation. In particular, the impact of two key parameters was studied here in an attempt to identify optimal preparation conditions: (a) different concentrations of the crosslinker EGDMA and (b) different porogen compositions while the monomer to porogen ratio was kept constant. Resulting monolithic phases were characterized in terms of permeability, mean pore diameter and swelling using three different eluents (water, acetonitrile and a mixture at maximum viscosity). First, the LMA/EGDMA monolithic phases present peculiar morphology and hydrodynamic properties for 37% by weight of EGDMA, as reflected by the peak observed for their permeability and mean pore diameter. Swelling experiments revealed the coexistence of two phases in the monolithic structure: a highly crosslinked rigid phase which was insensitive to swelling in the presence of solvent and a weakly crosslinked flexible phase exhibiting significant swelling, with a transition to such a biphasic behavior taking place at 37% by weight of EGDMA. The effects of porogen composition and network swelling properties are presented based on a combination of the Flory − Huggins theory of isotropic mixing in polymer solutions and the Flory − Rehner theory of rubber elasticity in the affine network approximation. © 2016 Society of Chemical Industry

Rapid “one-pot” preparation of polymeric monolith via photo-initiated thiol-acrylate polymerization for capillary liquid chromatography

A facile approach was exploited for fast preparation of polymer-based monoliths in UV-transparent fused-silica capillaries via “one-pot” photo-initiated thiol-acrylate polymerization reaction of dipentaerythritolpenta-/hexaacrylate (DPEPA) and 1-octadecanethiol (ODT) in the presence of porogenic solvents (1-butanol and ethylene glycol). Due to relative insensitivity of oxygen inhibition in thiol-ene free-radical polymerization, the polymerization could be performed within 5 min. The effects of composition of prepolymerization solution on the morphology and permeability of poly(ODT-co-DPEPA) monoliths were investigated in detail by adjusting the content of monomer and binary porogen ratio. The physical properties of poly(ODT-co-DPEPA) monoliths were characterized by Fourier transform infrared spectroscopy (FT-IR), mercury intrusion porosimetry (MIP) and nitrogen adsorption/desorption measurement. The evaluation of chromatographic performance was carried out by capillary liquid chromatography (cLC). The results indicated that the poly(ODT-co-DPEPA) monolith was homogeneous and permeable, and also possessed a typical reversed-phase retention mechanism in cLC with high efficiency (∼75,000 N m−1) for separation of alkylbenzenes. Eventually, the further separation of tryptic digest of proteins by cLC tandem mass spectrometry (cLC-MS/MS) demonstrated its potential in the analysis of biological samples.

Improving the permeability of lyophilized collagen–hydroxyapatite scaffolds for cell‐based bone regeneration with a gelatin porogen

Bone tissue engineering using biomaterial scaffolds and culture-expanded osteoprogenitor cells has been demonstrated in several studies; however, it is not yet a clinical reality. One challenge is the optimal design of scaffolds for cell delivery and the identification of scaffold parameters that can delineate success and failure in vivo. Motivated by a previous experiment in which a batch of lyophilized collagen-hydroxyapatite (HA) scaffolds displayed modest bone formation in vivo, despite having large pores and high porosity, we began to investigate the effect of scaffold permeability on bone formation. Herein, we fabricated scaffolds with a permeability of 2.17 ± 1.63 × 10-9 m4 /(N s) and fourfold higher using a sacrificial gelatin porogen. Scaffolds were seeded with mouse bone marrow stromal cells carrying a fluorescent reporter for osteoblast differentiation and implanted into critical-size calvarial defects in immunodeficient mice. The porogen scaffold group containing a 1:1 ratio of solids to beads was significantly more radiopaque than the scaffold group without the bead porogen 3 weeks after implantation. Quantitative histomorphometry uncovered the same trend between the 1:1 group and scaffolds without porogen found in the radiographic data; however, this was not statistically significant here. Taken together, the X-ray and histology suggest that the 1:1 ratio of porogen to scaffold solids, resulting in a fourfold increase in permeability, may enhance bone formation when compared to scaffolds without porogen. Scaffold permeability can be a useful quality control measure before implantation and this practice should improve the consistency and efficacy of cell-based bone tissue engineering. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1580-1590, 2016.