Redox-Responsive "Catch and Release" Cryogels: A Versatile Platform for Capture and Release of Proteins and Cells

Macroporous cryogels are attractive scaffolds for biomedical applications, such as biomolecular immobilization, diagnostic sensing, and tissue engineering. In this study, thiol-reactive redox-responsive cryogels with a porous structure are prepared using photopolymerization of a pyridyl disulfide poly(ethylene glycol) methacrylate (PDS-PEG-MA) monomer. Reactive cryogels are produced using PDS-PEG-MA and hydrophilic poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) monomers, along with a PEG-based cross-linker and photoinitiator. Functionalization of cryogels using a fluorescent dye via the disulfide-thiol exchange reactions is demonstrated, followed by release under reducing conditions. For ligand-mediated protein immobilization, first, thiol-containing biotin or mannose is conjugated onto the cryogels. Subsequently, fluorescent dye-labeled proteins streptavidin and concanavalin A (ConA) are immobilized via ligand-mediated conjugation. Furthermore, we demonstrate that the mannose-decorated cryogel could capture ConA selectively from a mixture of lectins. The efficiency of protein immobilization could be easily tuned by changing the ratio of the thiol-sensitive moiety in the scaffold. Finally, an integrin-binding cell adhesive peptide is attached to cryogels to achieve successful attachment, and the on-demand detachment of integrin-receptor-rich fibroblast cells is demonstrated. Redox-responsive cryogels can serve as potential scaffolds for a variety of biomedical applications because of their facile synthesis and modification.

Metal-Free Click-Chemistry: A Powerful Tool for Fabricating Hydrogels for Biomedical Applications

Increasing interest in the utilization of hydrogels in various areas of biomedical sciences ranging from biosensing and drug delivery to tissue engineering has necessitated the synthesis of these materials using efficient and benign chemical transformations. In this regard, the advent of "click" chemistry revolutionized the design of hydrogels and a range of efficient reactions was utilized to obtain hydrogels with increased control over their physicochemical properties. The ability to apply the "click" chemistry paradigm to both synthetic and natural polymers as hydrogel precursors further expanded the utility of this chemistry in network formation. In particular, the ability to integrate clickable handles at predetermined locations in polymeric components enables the formation of well-defined networks. Although, in the early years of "click" chemistry, the copper-catalyzed azide-alkyne cycloaddition was widely employed, recent years have focused on the use of metal-free "click" transformations, since residual metal impurities may interfere with or compromise the biological function of such materials. Furthermore, many of the non-metal-catalyzed "click" transformations enable the fabrication of injectable hydrogels, as well as the fabrication of microstructured gels using spatial and temporal control. This review article summarizes the recent advances in the fabrication of hydrogels using various metal-free "click" reactions and highlights the applications of thus obtained materials. One could envision that the use of these versatile metal-free "click" reactions would continue to revolutionize the design of functional hydrogels geared to address unmet needs in biomedical sciences.

Plug-and-Play Biointerfaces: Harnessing Host-Guest Interactions for Fabrication of Functional Polymeric Coatings

Polymeric surface coatings capable of effectively integrating desired functional molecules and ligands are attractive for fabricating bio-interfaces necessary for various applications. Herein, we report the design of a polymeric platform amenable to such modifications in a modular fashion through host-guest chemistry. Copolymers containing adamantane (Ada) moieties, diethylene glycol (DEG) units, and silyloxy groups to provide functionalization handles, anti-biofouling character, and surface attachment, respectively, were synthesized. These copolymers were employed to modify silicon/glass surfaces to enable their functionalization using beta-cyclodextrin (βCD) containing functional molecules and bioactive ligands. Moreover, surface functionalization could be spatially controlled using a well-established technique like microcontact printing. Efficient and robust functionalization of polymer-coated surfaces was demonstrated by immobilizing a βCD-conjugated fluorescent rhodamine dye through the specific noncovalent binding between Ada and βCD units. Furthermore, biotin, mannose, and cell adhesive peptide-modified βCD were immobilized onto the Ada-containing polymer-coated surfaces to direct noncovalent conjugation of streptavidin, concanavalin A (ConA), and fibroblast cells, respectively. It was demonstrated that the mannose-functionalized coating could selectively bind to the target lectin ConA, and the interface could be regenerated and reused several times. Moreover, the polymeric coating was adaptable for cell attachment and proliferation upon noncovalent modification with cell-adhesive peptides. One can envision that the facile synthesis of the Ada-based copolymers, mild conditions for coating surfaces, and their effective transformation to various functional interfaces in a modular fashion offers an attractive approach to engineering functional interfaces for several biomedical applications.

Aesthetic rehabilitation for anterior teeth of dental fluorosis with direct composite veneers

Intrinsic discoloration can be formed due to many reasons, and by clinical evaluation and history from the patient, the exact cause of the discoloration can be known and one of the reasons that can make the intrinsic discoloration is the high level of fluoride intake. Two siblings had come to the Department of Restorative Dentistry clinics; they had the same compliance which is severe dental fluorosis, caries, and malocclusion of their teeth. What is interesting and worrying is that some patients with severe dental fluorosis show higher levels of caries, which can be explained as the enamel becoming porous with severe fluorosis. The possible treatment options were discussed with the patients. According to their financial concern and their desire to get their teeth done as soon as possible, the use of direct composite veneer for the treatment of anterior teeth was decided. Long-term clinical trials are required to assess the efficacy of various treatment options for fluorosis of different severity.

“Clickable” Polymer Brush Interfaces: Tailoring Monovalent to Multivalent Ligand Display for Protein Immobilization and Sensing

Facile and effective functionalization of the interface of polymer-coated surfaces allows one to dictate the interaction of the underlying material with the chemical and biological analytes in its environment. Herein, we outline a modular approach that would enable installing a variety of “clickable” handles onto the surface of polymer brushes, enabling facile conjugation of various ligands to obtain functional interfaces. To this end, hydrophilic anti-biofouling poly(ethylene glycol)-based polymer brushes are fabricated on glass-like silicon oxide surfaces using reversible addition–fragmentation chain transfer (RAFT) polymerization. The dithioester group at the chain-end of the polymer brushes enabled the installation of azide, maleimide, and terminal alkene functional groups, using a post-polymerization radical exchange reaction with appropriately functionalized azo-containing molecules. Thus, modified polymer brushes underwent facile conjugation of alkyne or thiol-containing dyes and ligands using alkyne–azide cycloaddition, Michael addition, and radical thiol–ene conjugation, respectively. Moreover, we demonstrate that the radical exchange approach also enables the installation of multivalent motifs using dendritic azo-containing molecules. Terminal alkene groups containing dendrons amenable to functionalization with thiol-containing molecules using the radical thiol–ene reaction were installed at the interface and subsequently functionalized with mannose ligands to enable sensing of the Concanavalin A lectin.

Benzothiazole-disulfide based redox-responsive polymers: facile access to reversibly functionalizable polymeric coatings

Redox-responsive polymers and polymeric coatings containing benzothiazole-disulfide groups provide facile access to reversibly functionalizable platforms.

BODIPY and 2,3-Dihydrophthalazine-1,4-Dione Conjugates As Heavy Atom-Free Chemiluminogenic Photosensitizers

We disclose an interesting concept for developing heavy atom-free chemiluminogenic photosensitizers. To accomplish this, conjugates 2 and 3, which are composed of boron-dipyrromethene (BODIPY) and 2,3-dihydrophthalazine-1,4-dione units, are investigated. 2 and 3 are compared in terms of their photophysical properties, chemiluminescence responses, and singlet oxygen production. Strikingly, the results indicate that decoration of BODIPY with the 2,3-dihydrophthalazine-1,4-dione scaffold boosts the singlet oxygen generation. Furthermore, treatment of epidermoid laryngeal carcinoma Hep-2 (Hep-2) cells with conjugates 2 and 3 results in efficient cellular internalization which ensures live- cell imaging of Hep-2 cells. Finally, it is noteworthy that in vitro cytotoxicity assays reveal that both 2 and 3 induce cytotoxicity when illuminated with red light. Thus, 2 and 3 represent heavy atom-free chemiluminogenic photosensitizers.

Multifunctional and Transformable 'Clickable' Hydrogel Coatings on Titanium Surfaces: From Protein Immobilization to Cellular Attachment

Multifunctionalizable hydrogel coatings on titanium interfaces are useful in a wide range of biomedical applications utilizing titanium-based materials. In this study, furan-protected maleimide groups containing multi-clickable biocompatible hydrogel layers are fabricated on a titanium surface. Upon thermal treatment, the masked maleimide groups within the hydrogel are converted to thiol-reactive maleimide groups. The thiol-reactive maleimide group allows facile functionalization of these hydrogels through the thiol-maleimide nucleophilic addition and Diels-Alder cycloaddition reactions, under mild conditions. Additionally, the strained alkene unit in the furan-protected maleimide moiety undergoes radical thiol-ene reaction, as well as the inverse-electron-demand Diels-Alder reaction with tetrazine containing molecules. Taking advantage of photo-initiated thiol-ene 'click' reactions, we demonstrate spatially controlled immobilization of the fluorescent dye thiol-containing boron dipyrromethene (BODIPY-SH). Lastly, we establish that the extent of functionalization on hydrogels can be controlled by attachment of biotin-benzyl-tetrazine, followed by immobilization of TRITC-labelled ExtrAvidin. Being versatile and practical, we believe that the described multifunctional and transformable 'clickable' hydrogels on titanium-based substrates described here can find applications in areas involving modification of the interface with bioactive entities.

The effect of pregabalin and ibuprofen combination for pain after third molar surgery

Aim

The objective of this study was to compare the efficacy of different doses of pregabalin and intravenous ibuprofen with regard to pain management and analgesic consumption after third molar surgery.

Materials and Methods

Ninety patients who had been scheduled for third molar surgery were assigned to four different treatment groups. The inclusion criteria consisted of the presence of fully or partially bony retentive asymptomatic mandibular third molars. These groups are included the following: (Group 1) premedicated with oral placebo and intravenous (IV) placebo, (Group 2) premedicated with oral placebo and 400-mg IV Ibuprofen, (Group 3) premedicated with 75-mg oral pregabalin and 400-mg IV ibuprofen, and (Group 4) premedicated with 150-mg oral pregabalin and 400 mg IV ibuprofen. Postoperative pain was assessed with visual analog scale (VAS) every hour for the first 12 hs following the surgery. Pain was then assessed at different time intervals during 7 days following the surgery. Kruskal-Wallis tests were used to compare the four groups in terms of VAS pain scores, analgesic consumption, and first rescue analgesic request time after the surgery.

Results

At the end of the study, the results of 80 patients (20 patients per group) were analyzed. The group 4 had lower pain intensity compared with other groups at various time intervals. This difference is statistically significant in between the first 3-10 h (first day) and single-time intervals in second, third, fifth, and sixth postoperative days. Postoperative analgesic consumption was not statistically different between the groups. The first rescue analgesic request time after surgery was different between the pregabalin combination groups and group 2. No significant difference in the side effects was observed.

Conclusion

These findings suggest that preoperative coadministration of 150-mg pregabalin and IV ibuprofen may be useful in improving pain control after third molar surgery.

A phosphorescent fluoride probe based on Eu(ııı)-DO3A clicked with a 2,5-di(thien-2-yl)pyrrole scaffold

A novel material that can be used as a turn-on phosphorescent fluoride probe is designed and synthesized.

Embedding Well-Defined Responsive Hydrogels with Nanocontainers: Tunable Materials from Telechelic Polymers and Cyclodextrins

Design, synthesis, and application of cyclodextrin (CD) containing thermoresponsive hydrogels fabricated from thiol-reactive telechelic polymers are reported. Hydrophilic polymers containing 2-hydroxyethyl methacrylate and/or di(ethylene glycol)methylether methacrylate monomers as side chains and thiol-reactive groups at chain ends were synthesized. A series of hydrogels was fabricated using thiol-ene conjugation of these thiol-reactive polymers with multivalent thiol-containing CDs as crosslinkers. Clear and transparent hydrogels were obtained with good conversion (79-89%) by utilizing the "nucleophilic" and "radical" thiol-ene "click" reactions. Analysis of the amount of residual thiol groups in these hydrogels using Ellman's reagent suggested that gels with a moderately well-defined network structure were obtained. Hydrogels fabricated using different telechelic polymers were examined for their properties such as morphology, equilibrium water uptake, and rheological characteristics. Cytocompatibility of these hydrogels was ascertained by a cell viability assay that demonstrated low toxicity toward fibroblast cells. Thereafter, the CD-containing hydrogels were evaluated for the loading and controlled release of puerarin, an antiglaucoma drug. Utilization of thermoresponsive polymers as the matrix for these hydrogels allows use of temperature as a stimulus to modulate the drug release. A slower and more sustained drug release was observed at physiological temperatures compared to ambient conditions. The effect of temperature on the elasticity of the hydrogel was investigated rheologically to demonstrate that the collapse of the network structure occurs near physiological temperatures. The increased hydrophobicity and compactness of the gel matrix at higher temperatures results in a slower drug release. The strategy employed here demonstrates that tuning the matrix composition of hydrogels with well-defined network structures through appropriate choice of responsive copolymers allows design of materials with control of their physical properties and drug-release behavior.

Behaviour of Toxoplasma gondii RH Ankara strain tachyzoites during continuous production in various cell lines

Toxoplasma gondii is an obligate intracellular protozoan parasite. The objective of the present study was to examine the behaviour of Toxoplasma gondii RH Ankara strain tachyzoites in a cell culture environment. The study represents the first step in determining whether T. gondii RH Ankara strain tachyzoites, grown in cell culture, are of sufficient quality to allow cessation of in vivo tachyzoite production for diagnostic assays. In the present study, T. gondii RH Ankara strain tachyzoites were continuously produced in myeloma X63.Ag8.653, HeLa, Hep-2, and Vero cell cultures for 2 months. The average size of the tachyzoites was 3×5·7 μm prior to the first inoculation but after continuous production, a marked decrease was noted in average tachyzoite size. The smallest tachyzoite size, was 1×2·1 μm after 2 months, in myeloma cell cultures even though the yield of tachyzoites increased. With other cell cultures, tachyzoite yields were not as high as myeloma cell culture although decrease in size was less. The smallest decrease in tachyzoite size, averaging 2×3·8 μm after 2 months, was observed in tachyzoites produced in HeLa cell cultures. A virulence assay in small groups of BALB/c mice, using tachyzoites derived from cell cultures, was also conducted. The preliminary results of the virulence assay suggest that as the size of the tachyzoites decreased, the virulence in mice decreased. Future research will focus on the effect of the size of cell culture-derived T. gondii RH Ankara strain tachyzoites on the virulence, protein expression, and the reliability of diagnostic assays. Ultimately, the behaviour of tachyzoites from various T. gondii strains will be observed in cell culture to determine if size is altered.