Dextran-based nanoparticles with 5-FU-conjugated polymethacrylate segments for drug delivery: Synthesis of amphiphilic graft copolymers by mechanochemical solid-state polymerization and characterization.

Dextran (Dx) is a biodegradable and biocompatible polysaccharide, thus promising as a drug delivery carrier for tumor therapy. Herein, we applied mechanical energy to a high molecular weight Dx to control its molecular weight and simultaneously generate mechanoradicals. The solid-state polymerization of methacrylate- or methacrylamide derivatives initiated with Dx mechanoradicals showed polymer conversion of >95%, yielding Dx-based graft copolymers with molecular weights of approximately 30,000 g mol-1. The Dx-based graft copolymers with hydrophobic segments formed nanoparticles with a particle size of 25-35 nm in an aqueous solution. The anti-pancreatic tumor drug 5-fluorouracil (5-FU) was covalently conjugated onto the hydrophobic segments of the amphiphilic Dx, and the nanoparticles were also prepared. The drug release profile from 5-FU-conjugated nanoparticles corresponded well to the Korsmeyer-Peppas model applied to drug release from matrix substrates, and was also immensely predicted by the Logistic and Gompertz curves. The 5-FU-conjugated nanoparticles showed cytotoxicity against the pancreatic adenocarcinoma cell lines (BxPC-3) that were not significantly inferior to the 5-FU positive group. Furthermore, the fluorescein-labeled nanoparticles internalized into BxPC-3 within 6 h and actively migrated into the cytosol. These results suggest that Dx-based graft copolymers with hydrophobic segments might be used to enhance therapeutic activity.

Peculiar Behavior of Methyl Methacrylate Emulsion Polymerization-Induced Self-Assembly Mediated by RAFT Using Poly(Methacrylic Acid) Macromolecular Chain Transfer Agent.

Reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of methyl methacrylate (MMA) is successfully performed in water in the presence of a poly(methacrylic acid) (PMAA) macromolecular chain transfer agent (macroCTA) leading to the formation of self-stabilized PMAA-b-PMMA amphiphilic block copolymer particles. At pH 3.7, the reactions are well-controlled with narrow molar mass distributions. Increasing the initial pH, particularly above 5.6, results in a partial loss of reactivity of the PMAA macroCTA. The effect of the degree of polymerization (DPn) of the PMMA block, the solids content, the nature of the hydrophobic segment, and the pH on the morphology of the obtained diblock copolymer particles is then investigated. Worm-like micelles are formed for a DPn of PMMA of 20 (PMMA20), while "onion-like" particles and spherical vesicles are obtained for PMMA30 and PMMA50, respectively. In contrast, spherical particles are obtained for the DPns higher than 150. This unusual evolution of particle morphologies upon increasing the DPn of the PMMA block seems to be related to hydrogen bonds between hydrophilic MAA and hydrophobic MMA units.

Arginine-Functional Methacrylic Block Copolymer Nanoparticles: Synthesis, Characterization, and Adsorption onto a Model Planar Substrate.

Recently, we reported the synthesis of a hydrophilic aldehyde-functional methacrylic polymer (Angew. Chem., 2021, 60, 12032-12037). Herein we demonstrate that such polymers can be reacted with arginine in aqueous solution to produce arginine-functional methacrylic polymers without recourse to protecting group chemistry. Careful control of the solution pH is essential to ensure regioselective imine bond formation; subsequent reductive amination leads to a hydrolytically stable amide linkage. This new protocol was used to prepare a series of arginine-functionalized diblock copolymer nanoparticles of varying size via polymerization-induced self-assembly in aqueous media. Adsorption of these cationic nanoparticles onto silica was monitored using a quartz crystal microbalance. Strong electrostatic adsorption occurred at pH 7 (Γ = 14.7 mg m-2), whereas much weaker adsorption occurred at pH 3 (Γ = 1.9 mg m-2). These findings were corroborated by electron microscopy, which indicated a surface coverage of 42% at pH 7 but only 5% at pH 3.

Coffee Beverage: A New Strategy for the Synthesis of Polymethacrylates via ATRP.

Coffee, the most popular beverage in the 21st century society, was tested as a reaction environment for activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) without an additional reducing agent. Two blends were selected: pure Arabica beans and a proportional blend of Arabica and Robusta beans. The use of the solution received from the mixture with Robusta obtained a high molecular weight polymer product in a short time while maintaining a controlled structure of the synthesized product. Various monomers with hydrophilic characteristics, i.e., 2-(dimethylamino)ethyl methacrylate (DMAEMA), oligo(ethylene glycol) methyl ether methacrylate (OEGMA500), and glycidyl methacrylate (GMA), were polymerized. The proposed concept was carried out at different concentrations of coffee grounds, followed by the determination of the molar concentration of caffeine in applied beverages using DPV and HPLC techniques.

Phenylboronic Acid Modification Augments the Lysosome Escape and Antitumor Efficacy of a Cylindrical Polymer Brush-Based Prodrug.

Timely lysosome escape is of paramount importance for endocytosed nanomedicines to avoid premature degradation under the acidic and hydrolytic conditions in lysosomes. Herein, we report an exciting finding that phenylboronic acid (PBA) modification can greatly facilitate the lysosome escape of cylindrical polymer brushes (CPBs). On the basis of our experimental results, we speculate that the mechanism is associated with the specific interactions of the PBA groups with lysosomal membrane proteins and hot shock proteins. The featured advantage of the PBA modification over the known lysosome escape strategies is that it does not cause significant adverse effects on the properties of the CPBs; on the contrary, it enhances remarkably their tumor accumulation and penetration. Furthermore, doxorubicin was conjugated to the PBA-modified CPBs with a drug loading content larger than 20%. This CPBs-based prodrug could eradicate the tumors established in mice by multiple intravenous administrations. This work provides a novel strategy for facilitating the lysosome escape of nanomaterials and demonstrates that PBA modification is an effective way to improve the overall properties of nanomedicines including the tumor therapeutic efficacy.

Multifunctional Size-Expandable Nanomedicines Enhance Tumor Accumulation and Penetration for Synergistic Chemo-Photothermal Therapy.

Size expansion can effectively improve tumor accumulation of nanocarriers where precise control is required. A dual-responsive nanocarrier stimulated by both endogenous pH and exogenous heat stimuli can change its size. Herein, a nanoparticle composed of poly(N,N-diethyl acrylamide) (PDEAA) and poly(2-(diisopropylamino) ethyl methacrylate) (PDPA) is developed. The antitumor drug celastrol (CLT) and the photosensitizer indocyanine green (ICG) are then loaded in it to form CIPP. ICG generates heat under near-infrared (NIR) stimulation to kill tumor cells and enhance CIPP penetration. Meanwhile, CIPP expands in response to hyperthermia and acid tumor microenvironments, preventing itself from returning to the blood flow, thus accumulating in tumor sites. Ultimately, the acidic lysosomal environment in tumor cells disintegrates CIPP to release CLT, directly inducing immunogenic cell death and sensitizing tumor cells for hyperthermia by disrupting the interaction of heat shock protein 90 and P50cdc37. Most of the tumors in B16F10-bearing mice are eradicated after single laser irradiation. The dual-responsive CIPP with multiple functions and simple design displays a synergistic antitumor effect. This study provides a basis for developing size-expandable stimulus-responsive drug delivery systems against tumors.

Gingipain-Responsive Thermosensitive Hydrogel Loaded with SDF-1 Facilitates In Situ Periodontal Tissue Regeneration.

Existing local drug delivery systems for periodontitis suffer from poor antibacterial effect and unsatisfied periodontal regeneration. In this study, a smart gingipain-responsive hydrogel (PEGPD@SDF-1) was synthesized as an environmentally sensitive carrier for on-demand drug delivery. The PEGPD@SDF-1 hydrogel was synthesized from polyethylene glycol diacrylate (PEG-DA) based scaffolds, dithiothreitol (DTT), and a novel designed functional peptide module (FPM) via Michael-type addition reaction, and the hydrogel was further loaded with stromal cell derived factor-1 (SDF-1). The FPM exhibiting a structure of anchor peptide-short antimicrobial peptide (SAMP)-anchor peptide could be cleaved by gingipain specifically, and the SAMP was released out of the hydrogel for antibacterial effect in response to gingipain. The hydrogel properties were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), swelling ratio analysis, degradation evaluation, and release curve description of the SAMP and SDF-1. Results in vitro indicated the PEGPD@SDF-1 hydrogel exhibited preferable biocompatibility and could promote the proliferation, migration, and osteogenic differentiation of periodontal ligament stem cells (PDLSCs). Antibacterial testing demonstrated that the PEGPD@SDF-1 hydrogel released the SAMP stressfully in response to gingipain stimulation, thereby strongly inhibiting the growth of Porphyromonas gingivalis. Furthermore, the study in vivo indicated that the PEGPD@SDF-1 hydrogel inhibited P. gingivalis reproduction, created a low-inflammatory environment, facilitated the recruitment of CD90+/CD34- stromal cells, and induced osteogenesis. Taken together, these results suggest that the gingipain-responsive PEGPD@SDF-1 hydrogel could facilitate in situ periodontal tissue regeneration and is a promising candidate for the on-demand local drug delivery system for periodontitis.

Development of Gelucire® 48/16 and TPGS Mixed Micelles and Its Pellet Formulation by Extrusion Spheronization Technique for Dissolution Rate Enhancement of Curcumin.

The oral bioavailability of curcumin is limited, attributed to its low solubility or dissolution and poor absorption. Herein, the study describes formulation of curcumin-loaded mixed micelles of Gelucire® 48/16 and TPGS for its dissolution rate enhancement. Curcumin was dispersed in these molten lipidic surfactants which was then adsorbed on carrier and formulated as pellets by extrusion spheronization. Critical micelle concentration (CMC) of binary mixture of Gelucire® 48/16 and TPGS was lower than their individual CMC demonstrating the synergistic behavior of mixture. Thermodynamic parameters like partition coefficient and Gibbs free energy of solubilization indicated that mixed micelles were more efficient than micelles of its individual components in curcumin solubilization. Dynamic light scattering (DLS) suggested slight increase in micellar size of mixed micelles than its components suggesting curcumin loading in mixed micelles. Fourier transform infrared spectroscopy (FTIR) revealed that phenolic hydroxyl group interacts with lipids which contribute to its enhanced solubility. Furthermore, the differential scanning calorimetry (DSC) and X-ray diffraction (XRD) study indicated the conversion of crystalline curcumin into amorphous form. In the pellet formulation, Gelucire® 48/16 acted as a binder and eliminated the requirement of additional binder. Microcrystalline cellulose (MCC) forms wet mass and retards the release of curcumin from pellets. Increase in concentration of water-soluble diluent increased drug release. The optimized formulation released more than 90% drug and maintains supersaturation level of curcumin for 2 h. Thus, mixed micellar system was effective delivery system for curcumin while pellet formulation is an interesting formulation strategy consisting semi-solid lipids.

Photocurable Biopolymers for Coaxial Bioprinting.

Thanks to their unique advantages, additive manufacturing technologies are revolutionizing almost all sectors of the industrial and academic worlds, including tissue engineering and regenerative medicine. In particular, 3D bioprinting is rapidly emerging as a first-choice approach for the fabrication-in one step-of advanced cell-laden hydrogel constructs to be used for in vitro and in vivo studies. This technique consists in the precise deposition layer-by-layer of sub-millimetric hydrogel strands in which living cells are embedded. A key factor of this process consists in the proper formulation of the hydrogel precursor solution, the so-called bioink. Ideal bioinks should be able, on the one side, to support cell growth and differentiation and, on the other, to allow the high-resolution deposition of cell-laden hydrogel strands. The latter feature requires the extruded solution to instantaneously undergo a sol-gel transition to avoid its collapse after deposition.To address this challenge, researchers are recently focusing their attention on the synthesis of several derivatives of natural biopolymers to enhance their printability. Here, we present an approach for the synthesis of photocurable derivatives of natural biopolymers-namely, gelatin methacrylate, hyaluronic acid methacrylate, chondroitin sulfate methacrylate, and PEGylated fibrinogen-that can be used to formulate tailored innovative bioinks for coaxial-based 3D bioprinting applications.

Shape-transformation of polymersomes from glassy and crosslinkable ABA triblock copolymers.

Recent developments in the field of polymer vesicles, i.e. polymersomes, have demonstrated that disrupting the equilibrium conditions of the milieu could lead to shape transformation into stable non-spherical morphologies, bringing on-demand shape control to reality and bearing great promise for cell mimicry and a variety of biomedical applications. Here, we studied the self-assembly behavior of glassy amphiphilic triblock copolymers, poly(ethylene glycol)-block-polystyrene-stat-poly(coumarin methacrylate)-block-poly(ethylene glycol) (PEG-b-P(S-stat-CMA)-b-PEG), and their response to various stimuli. By changing the respective molecular weights of both the hydrophobic P(S-stat-CMA) and the hydrophilic PEG blocks, we varied the hydrophobic volume fraction thereby accessing a range of morphologies from spherical and worm-like micelles, as well as polymersomes. For the latter, we observed that slow osmotic pressure changes induced by dialysis led to a decrease in size while rapid osmotic pressure changes by addition of a PEG fusogen led to morphological transformations into rod-like and tubular polymersomes. We also found out that chemically crosslinking the vesicles before inducing osmotic pressure changes led to the vesicles exhibiting hypotonic shock, atypical for glassy polymersomes. We believe that this approach combining the robustness of triblock copolymers and light-based transformations will help expand the toolbox to design ever more complex biomimetic constructs.

Synthesis and characterization of thermo/pH-sensitive pectin-graft-poly(dimethylaminoethyl methacrylate) coated magnetic nanoparticles.

Herein, thermo- and pH-sensitive pectin-graft-poly(dimethylaminoethyl methacrylate) copolymer-coated magnetic nanoparticles were synthesized via a green and rapid synthetic approach based on microwave irradiation. Firstly, a novel thermo- and pH-sensitive pectin-graft-poly(dimethylaminoethyl methacrylate) copolymer (Pec-g-PolyDMAEMA) was synthesized and then, Pec-g-PolyDMAEMA based magnetic nanoparticles (Pec-g-PolyDMAEMA@Fe3O4) were produced via microwave-assisted co-precipitation method. The thermo/pH/magnetic field multi-sensitive hybrid nanoparticle was characterized by techniques like TEM, VSM, FT-IR, and TGA/DSC. In vitro release studies of 5-Fluorouracil (FL) were carried out by altering the temperature (37 and 44°C), pH (5.5 and 7.4) and presence of an AMF. The FL release of Pec-g-PolyDMAEMA@Fe3O4@FL exhibited pH-sensitive behavior. They showed thermo/pH-sensitive FL release features with the greatest release of FL at 37°C (56%) than at 44°C (40%) and at pH of 7.4 (63%) than at pH of 5.5 (45%) within 48h. The FL release was also significantly increased (100%) with the presence of a 50 mT magnetic field. These results indicate that the developed Pec-g-PolyDMAEMA@Fe3O4 nanoparticles are promising in the application of multi-stimuli-sensitive delivery of drugs.

A single-step preparation of carbohydrate functionalized monoliths for separation and trapping of polar compounds.

A single-step copolymerization strategy was developed for the preparation of carbohydrate (glucose and maltose) functionalized monoliths using click reaction. Firstly, novel carbohydrate-functionalized methacrylate monomers were synthesized through Cu(I)-catalyzed 1,3-dipolar cycloaddition (alkyne-azide reaction) of terminal alkyne with azide of carbohydrate derivatives. The corresponding carbohydrate functionalized monolithic columns were then prepared through a single-step in-situ copolymerization. The physicochemical properties and performance of the fabricated monolithic columns were evaluated using scanning electron microscopy, Fourier-transform infrared spectroscopy, and nano-liquid chromatography. For the optimized monolithic column, satisfactory column permeability and good separation performance were demonstrated for polar compounds including nucleoside, phenolic compounds and benzoic acid derivatives. The monolithic column is also highly useful for selective and efficient enrichment of glycopeptides from human IgG tryptic digests. This study not only provided a novel hydrophilic column for separation and selective trapping of polar compounds, but also proposed a facile and efficient approach for preparing carbohydrate functionalized monoliths.

Synthesis and characterization of pH sensitive hydrogel nanoparticles based on poly(N-isopropyl acrylamide-co-methacrylic acid).

In this work, pH-sensitive hydrogel nanoparticles based on N-isopropyl acrylamide (NIPAM) and methacrylic acid (MAA) at various molar ratios, were synthesized and characterized in terms of physicochemical and biological properties. FTIR and 1HNMR spectra confirmed the successful synthesis of the copolymer that formed nanoparticles. AFM images and FE-SEM micrographs showed that nanoparticles were spherical, but their round-shape was slightly compromised with MAA content; besides, the size of particles tends to decrease as MAA content increased. The hydrogels nanoparticles also exhibited an interesting pH-sensitivity, displaying changes in its particle size when changes in pH media occurred. Biological characterization results indicate that all the synthesized particles are non-cytotoxic to endothelial cells and hemocompatible, although an increase of MAA content leads to a slight increase in the hemolysis percentage. Therefore, the pH-sensitivity hydrogels may serve as a versatile platform as self-regulated drug delivery systems in response to environmental pH changes.

Artificial Neural Network (ANN) Approach to Predict an Optimized pH-Dependent Mesalamine Matrix Tablet.

BACKGROUND: Severe bleeding and perforation of the colon and rectum are complications of ulcerative colitis which can be treated by a targeted drug delivery system. PURPOSE: Development of colon-targeted delivery usually involves a complex formulation process and coating steps of pH-sensitive methacrylic acid based Eudragit®. The current work was purposefully designed to develop dicalcium phosphate (DCP) facilitated with Eudragit-S100-based pH-dependent, uncoated mesalamine matrix tablets. MATERIALS AND METHODS: Mesalamine formulations were compressed using wet granulation technique with varying compositions of dicalcium phosphate (DCP) and Eudragit-S100. The developed formulations were characterized for physicochemical and drug release profiles. Infrared studies were carried out to ensure that there was no interaction between active ingredients and excipients. Artificial neural network (ANN) was used for the optimization of final DCP-Eudragit-S100 complex and the experimental data were employed to train a multi-layer perception (MLP) using quick propagation (QP) training algorithm until a satisfactory root mean square error (RMSE) was reached. The ANN-aided optimized formulation was compared with commercially available Masacol®. RESULTS: Compressed tablets met the desirability criteria in terms of thickness, hardness, weight variation, friability, and content uniformity, ie, 5.34 mm, 7.7 kg/cm2, 585±5 mg (%), 0.44%, and 103%, respectively. In-vitro dissolution study of commercially available mesalamine and optimized formulation was carried out and the former showed 100% release at 6 h while the latter released only 12.09% after 2 h and 72.96% after 12 h which was fitted to Weibull release model with b value of 1.3, indicating a complex release mechanism. CONCLUSION: DCP-Eudragit-S100 blend was found explicative for mesalamine release without coating in gastric and colonic regions. This combination may provide a better control of ulcerative colitis.

Preparation of Poly(glycidyl methacrylate) (PGMA) and Amine Modified PGMA Adsorbents for Purification of Glucosinolates from Cruciferous Plants.

Glucosinolates (GLs) are of great interest for their potential as antioxidant and anticancer compounds. In this study, macroporous crosslinked copolymer adsorbents of poly (glycidyl methacrylate) (PGMA) and its amine (ethylenediamine, diethylamine, triethylamine)-modified derivatives were prepared and used to purify the GLS glucoerucin in a crude extract obtained from a cruciferous plant. These four adsorbents were evaluated by comparing their adsorption/desorption and decolorization performance for the purification of glucoerucin from crude plant extracts. According to the results, the strongly basic triethylamine modified PGMA (PGMA-III) adsorbent showed the best adsorption and desorption capacity of glucoerucin, and its adsorption data was a good fit to the Freundlich isotherm model and pseudo-second-order kinetics; the PGMA adsorbent gave the optimum decolorization performance. Furthermore, dynamic adsorption/desorption experiments were carried out to optimize the purification process. Two glass columns were serially connected and respectively wet-packed with PGMA and PGMA-III adsorbents so that glucoerucin could be decolorized and isolated from crude extracts in one process. Compared with KCl solution, aqueous ammonia was a preferable desorption solvent for the purification of glucoerucin and overcame the challenges of desalination efficiency, residual methanol and high operation costs. The results showed that after desorption with 10% aqueous ammonia, the purity of isolated glucoerucin was 74.39% with a recovery of 80.63%; after decolorization with PGMA adsorbent, the appearance of glucoerucin was improved and the purity increased by 11.30%. The process of using serially connected glass columns, wet-packed with PGMA and PGMA-III, may provide a simple, low-cost, and efficient method for the purification of GLs from cruciferous plants.

Polypyrrole and polyaniline nanocomposites with high photothermal conversion efficiency.

The simple and scalable synthesis of poly[2-(methacryloyloxy)ethyl phosphorylcholine] (PMPC)-coated conducting polymer (CP) nanocomposites is described. These functional nanocomposites exhibit tunable absorption in the near-infrared region with relatively high photothermal efficiencies. More importantly, their potential for bio-imaging and therapeutic treatment is proven by cellular uptake and cytotoxicity studies.

Cytocompatible and non-fouling zwitterionic hyaluronic acid-based hydrogels using thiol-ene "click" chemistry for cell encapsulation.

In this work, a facile click reaction strategy is employed to form hydrogels in situ with cytocompatibility, biodegradability, self-healing property and resistance to protein. The thiol-functionalized zwitterionic carboxybetaine methacrylate copolymer, which take part as a cross-linker in the "thiol-ene" click reaction with the methacrylated hyaluronic acid. The hydrogels are obtained under the physiological condition without the presence of any copper catalyst and UV light. The hydrogel consisting of zwitterionic component shows an obvious reduction in protein adsorption and cell adhesion and avoid non-targeted factor interference in the biological experiments. The hydrogels also demonstrate adjustable degradation behavior. Human mesenchymal stem cells (hMSCs) are easily encapsulated into the hydrogels and remains metabolically active, indicating the excellent biocompatibility of the hydrogels. Additionally, the result of the cytokine secretion assays (IL-6 and TNF-α) has shown that this clickable hydrogel can serve to suppress inflammatory reactions and is beneficial for in vivo applications. Based on the above results, this clickable hydrogel with excellent performance can be an amenable platform for 3D cell encapsulation.

Stimulus-Responsive Polyzwitterionic Surfaces Made from Itaconic Acid: Self-Triggered Antimicrobial Activity, Protein Repellency, and Cell Compatibility.

A functional monomer carrying a carboxylate and a protected primary ammonium group is synthesized from itaconic acid. When copolymerized with dimethyl acrylamide and 4-methacryloyloxybenzophenone, cross-linkable polyzwitterions are obtained. These are converted to surface-attached polyzwitterion networks by simultaneous UV-triggered C,H insertion reactions. The resulting polyzwitterion-coated substrates were studied by surface plasmon resonance spectroscopy measurements, ζ potential and various biological assays. They were (expectedly) protein repellent, yet at the same time (and unexpectedly) cell-adhesive and antimicrobially active. This was attributed to stimulus-responsiveness of the polyzwitterion (confirmed by the ζ potential measurements), which enables charge adjustment at different pH values. When protonated, the polyzwitterions become amphiphilic polycations and, in this state, kill bacteria upon contact like their parent structures (polymer-based synthetic mimics of antimicrobial peptides, SMAMPs).

Synthesis and in vitro cytotoxicity evaluation of star-shaped polymethacrylic conjugates with methotrexate or acitretin as potential antipsoriatic prodrugs.

Water-soluble polymer-drug conjugates were obtained and analyzed towards their potential use as prodrugs for two hydrophobic antipsoriatic agents, including methotrexate (MTX) and acitretin (AC). The conjugation efficacy of MTX decreased with a decreasing molar ratio of N,N-dimethylaminoethyl methacrylate (DMAEMA) repeating units in the polymethacrylic chains. Cytotoxicity of positively charged (from +5 to +10 mV) nano- and microparticles (3-1500 nm in DMEM at 37 °C) were estimated by in vitro MTT and Annexin-V apoptosis assays on Me45, NHDF, HaCaT and BEAS-2B cell lines. Further, cell cycle analysis revealed arrest in G0/G1 phase in melanoma cells, while neither apoptosis induction nor cell cycle arrest occurred in normal epidermal and epithelial cells. Tested conjugates displayed a novel cytostatic effect in Me45 cells and a pro-apoptotic effect in HaCaT cells. Epithelial BEAS-2B cells were the most sensitive to the tested conjugates and responded via induction of necrosis. Cell line models allowed for characterization of the biologically relevant potential action of pro-drugs. Additionally, a skin in vitro evaluation assay provided the first known evidence of side-effect reduction with pro-drug use. Histological examinations confirmed the lack of negative effects of conjugates on the skin and showed no irritating properties.

Influence of photo-initiators in the preparation of methacrylate monoliths into poly(ethylene-co-tetrafluoroethylene) tubing for microbore HPLC.

In this study, poly(butyl methacrylate-co-ethyleneglycol dimethacrylate) polymeric monoliths were in situ developed within 0.75 mm i.d. poly(ethylene-co-tetrafluoroethylene) (ETFE) tubing by UV polymerization via three different free-radical initiators (α,α'-azobisisobutyronitrile (AIBN), 2,2-dimethoxy-2-phenylacetophenone (DMPA) and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMPP). The influence of the nature of each photo-initiator and irradiation time on the morphological features of the polymer was investigated by scanning electron microscopy, and the chromatographic properties of the resulting microbore columns were evaluated using alkyl benzenes as test substances. The beds photo-initiated with MTMPP gave the best performance (minimum plate heights of 38 µm for alkyl benzenes) and exhibited a satisfactory reproducibility in the chromatographic parameters (RSD < 11%). These monolithic columns were also successfully applied to the separation of phenylurea herbicides, proteins and a tryptic digest of ß-casein.