Cycloaddition Reaction ; Molecular Structure ; Alkadienes

OBJECTIVES: To design and prepare silk fibroin/hyaluronic acid composite hydrogel. METHODS: The thiol modified silk fibroin and the double-bond modified hyaluronic acid were rapidly cured into gels through thiol-ene click polymerization under ultraviolet light condition. The grafting rate of modified silk fibroin and hyaluronic acid was characterized by ¹H NMR spectroscopy; the gel point and the internal microstructure of hydrogels were characterized by rheological test and scanning electron microscopy; the mechanical properties were characterized by compression test; the swelling rate and degradation rate were determined by mass method. The hydrogel was co-cultured with the cells, the cytotoxicity was measured by the lactate dehydrogenase method, the cell adhesion was measured by the float count method, and the cell growth and differentiation on the surface of the gel were observed by scanning electron microscope and fluorescence microscope. RESULTS: The functional group substitution degrees of modified silk fibroin and hyaluronic acid were 17.99% and 48.03%, respectively. The prepared silk fibroin/hyaluronic acid composite hydrogel had a gel point of 40-60 s and had a porous structure inside the gel. The compressive strength was as high as 450 kPa and it would not break after ten cycles. The water absorption capacity of the composite hydrogel was 4-10 times of its own weight. Degradation experiments showed that the hydrogel was biodegradable, and the degradation rate reached 28%-42% after 35 d. The cell biology experiments showed that the cytotoxicity of the composite gel was low, the cell adhesion was good, and the growth and differentiation of the cells on the surface of the gel were good. CONCLUSIONS The photocurable silk fibroin/hyaluronic acid composite hydrogel can form a gel quickly, and has excellent mechanical properties, adjustable swelling rate and degradation degree, good biocompatibility, so it has promising application prospects in biomedicine.
Fibroins/chemistry* ; Hydrogels/chemistry* ; Hyaluronic Acid/chemistry* ; Biocompatible Materials/chemistry* ; Click Chemistry ; Sulfhydryl Compounds ; Silk/chemistry*

The computer information technology that has penetrated into every aspect of our lives, can not only assist the screening of drugs, but also simulate the effect of drugs. At present, computer-aided technologies have been used to screen aptamers, which play an important role in improving the screening efficiency and screening high affinity binding aptamers. This review summarized the screening methods of aptamers through computer-aided sequence evaluation, structural analysis and molecular docking.
Aptamers, Nucleotide ; Computers ; Molecular Docking Simulation ; SELEX Aptamer Technique/methods*

Aptamers are single-stranded DNA or RNA which are isolated from synthesized random oligonucleotide library in vitro via systematic evolution of ligands by exponential enrichment (SELEX) and can bind to metal ions, small molecules, carbohydrates, lipids, proteins, and others targets with high affinity and specificity. Aptamers have the advantages of simple preparation, good thermal stability, and low immunogenicity and have great potential in the medical fields such as molecular imaging, biosensing, early diagnosis of diseases, and targeted therapy. Aptamer technology may be useful for early diagnosis and targeted therapy of pediatric cancer, and may avoid the side effects of conventional chemotherapy, such as growth and development disorders and long-term organ dysfunction. This article reviews the latest research advances in the selection and application of aptamers for pediatric cancer.
Child ; Early Detection of Cancer ; Humans ; Molecular Targeted Therapy ; Neoplasms ; diagnosis ; drug therapy ; SELEX Aptamer Technique ; methods

PURPOSE: We developed a Tc-99m and fluorescence-labeled peptide, Tc-99m TAMRA-GHEG-ECG-GNQWFI, to target tumor cells, and evaluated the diagnostic performance as a dual-modality imaging agent for tumor in a murine model.METHODS: TAMRA-GHEG-ECG-GNQWFI was synthesized using Fmoc solid-phase peptide synthesis. Radiolabeling of TAMRA-GHEG-ECG-GNQWFI with Tc-99m was done using ligand exchange via tartrate. Binding affinity and in vitro cellular uptake studies were performed. Gamma camera imaging, biodistribution, and ex vivo imaging studies were performed in murine models with U87MG tumors. Tumor tissue slides were prepared and analyzed with immunohistochemistry using confocal microscopy.RESULTS: After radiolabeling procedures with Tc-99m, Tc-99m TAMRA-GHEG-ECG-GNQWFI complexes were prepared in high yield (> 95%). The K(d) of Tc-99m TAMRA-GHEG-ECG-GNQWFI determined by saturation binding was 29.5 ± 4.5 nM. Confocal microscopy images of U87MG cells incubated with TAMRA-GHEG-ECG-GNQWFI showed strong fluorescence in the cytoplasm. Gamma camera imaging revealed substantial uptake of Tc-99m TAMRA-GHEG-ECG-GNQWFI in tumors. Tumor uptake was effectively blocked by the co-injection of an excess concentration of GNQWFI. Specific uptake of Tc-99m TAMRA-GHEG-ECG-GNQWFI was assessed by biodistribution, ex vivo imaging, and immunohistochemistry stain studies.CONCLUSION: In vivo and in vitro studies revealed substantial and specific uptake of Tc-99m TAMRA-GHEG-ECG-GNQWFI in tumor cells. Tc-99m TAMRA-GHEG-ECG-GNQWFI could be a good candidate dual-modality imaging agent for tumors.
Cytoplasm ; Fluorescence ; Immunohistochemistry ; In Vitro Techniques ; Microscopy, Confocal ; Multimodal Imaging ; Radionuclide Imaging ; Solid-Phase Synthesis Techniques

Novel hydrogel composed of both chondroitin sulfate (CS) and gelatin was developed for better cellular interaction through two step double crosslinking of N-(3-diethylpropyl)-N-ethylcarbodiimide hydrochloride (EDC) chemistries and then click chemistry. EDC chemistry was proceeded during grafting of amino acid dihydrazide (ADH) to carboxylic groups in CS and gelatin network in separate reactions, thus obtaining CS–ADH and gelatin–ADH, respectively. CS–acrylate and gelatin–TCEP was obtained through a second EDC chemistry of the unreacted free amines of CS–ADH and gelatin–ADH with acrylic acid and tri(carboxyethyl)phosphine (TCEP), respectively. In situ CS–gelatin hydrogel was obtained via click chemistry by simple mixing of aqueous solutions of both CS–acrylate and gelatin–TCEP. ATR-FTIR spectroscopy showed formation of the new chemical bonds between CS and gelatin in CS–gelatin hydrogel network. SEM demonstrated microporous structure of the hydrogel. Within serial precursor concentrations of the CS–gelatin hydrogels studied, they showed trends of the reaction rates of gelation, where the higher concentration, the quicker the gelation occurred. In vitro studies, including assessment of cell viability (live and dead assay), cytotoxicity, biocompatibility via direct contacts of the hydrogels with cells, as well as measurement of inflammatory responses, showed their excellent biocompatibility. Eventually, the test results verified a promising potency for further application of CS–gelatin hydrogel in many biomedical fields, including drug delivery and tissue engineering by mimicking extracellular matrix components of tissues such as collagen and CS in cartilage.
Amines ; Cartilage ; Cell Survival ; Chemistry ; Chondroitin Sulfates ; Chondroitin ; Click Chemistry ; Collagen ; Extracellular Matrix ; Gelatin ; Hydrogel ; Hydrogels ; In Vitro Techniques ; Spectrum Analysis ; Tissue Engineering ; Transplants

BACKGROUND: The tissue engineering and regenerative medicine approach require biomaterials which are biocompatible, easily reproducible in less time, biodegradable and should be able to generate complex three-dimensional (3D) structures to mimic the native tissue structures. Click chemistry offers the much-needed multifunctional hydrogel materials which are interesting biomaterials for the tissue engineering and bioprinting inks applications owing to their excellent ability to form hydrogels with printability instantly and to retain the live cells in their 3D network without losing the mechanical integrity even under swollen state. METHODS: In this review, we present the recent developments of in situ hydrogel in the field of click chemistry reported for the tissue engineering and 3D bioinks applications, by mainly covering the diverse types of click chemistry methods such as Diels–Alder reaction, strain-promoted azide-alkyne cycloaddition reactions, thiol-ene reactions, oxime reactions and other interrelated reactions, excluding enzyme-based reactions. RESULTS: The click chemistry-based hydrogels are formed spontaneously on mixing of reactive compounds and can encapsulate live cells with high viability for a long time. The recent works reported by combining the advantages of click chemistry and 3D bioprinting technology have shown to produce 3D tissue constructs with high resolution using biocompatible hydrogels as bioinks and in situ injectable forms. CONCLUSION: Interestingly, the emergence of click chemistry reactions in bioink synthesis for 3D bioprinting have shown the massive potential of these reaction methods in creating 3D tissue constructs. However, the limitations and challenges involved in the click chemistry reactions should be analyzed and bettered to be applied to tissue engineering and 3D bioinks. The future scope of these materials is promising, including their applications in in situ 3D bioprinting for tissue or organ regeneration.
Biocompatible Materials ; Bioprinting* ; Click Chemistry ; Cycloaddition Reaction ; Hydrogel* ; Hydrogels* ; Ink* ; Regeneration ; Regenerative Medicine ; Tissue Engineering*

We synthesized C-10 substituted triazolyl artemisinins by the Huisgen cycloaddition reaction between dihydroartemisinins (2) and variously substituted 1, 2, 3-triazoles (8a-8h). The antimalarial activities of 32 novel artemisinin derivatives were screened against a chloroquine-resistant parasite. Among them, triazolyl artemisinins with electron-withdrawing groups showed stronger antimalarial activities than those shown by the derivatives having electron-donating groups. In particularly, m-chlorotriazolyl artemisinin (9d-12d) showed antimalarial activity equivalent to that of artemisinin and could be a strong drug candidate.
Artemisinins ; Cycloaddition Reaction ; Parasites

Correct diagnosis and successful therapy are extremely important to enjoy a healthy life when suffering from a disease. To achieve these aims, various cutting-edge technologies have been designed and fabricated to diagnose and treat specific diseases. Among these technologies, aptamer–nanomaterial hybrids have received considerable attention from scientists and doctors because they have numerous advantages over other methods, such as good biocompatibility, low immunogenicity and controllable selectivity. In particular, aptamers, oligonucleic acids or peptides that bind to a specific target molecule, are regarded as outstanding biomolecules. In this review, several screening techniques for aptamers, also called systematic evolution of ligands by exponential enrichment (SELEX) methods, are introduced, and diagnostic and therapeutic aptamer applications are also presented. Furthermore, we describe diverse aptamer–nanomaterial conjugate designs and their applications for diagnosis and therapy.
Diagnosis ; Mass Screening ; Peptides ; SELEX Aptamer Technique

RNA-binding protein exerts important biological function by specifically recognizing RNA motif. SELEX (Systematic evolution of ligands by exponential enrichment), an in vitro selection method, can obtain consensus motif with high-affinity and specificity for many target molecules from DNA or RNA libraries. Here, we combined SELEX with next-generation sequencing to study the protein-RNA interaction in vitro. A pool of RNAs with 20 bp random sequences were transcribed by T7 promoter, and target protein was inserted into plasmid containing SBP-tag, which can be captured by streptavidin beads. Through only one cycle, the specific RNA motif can be obtained, which dramatically improved the selection efficiency. Using this method, we found that human hnRNP A1 RRMs domain (UP1 domain) bound RNA motifs containing AGG and AG sequences. The EMSA experiment indicated that hnRNP A1 RRMs could bind the obtained RNA motif. Taken together, this method provides a rapid and effective method to study the RNA binding specificity of proteins.
Aptamers, Nucleotide ; Gene Library ; Heterogeneous Nuclear Ribonucleoprotein A1 ; genetics ; High-Throughput Nucleotide Sequencing ; Humans ; RNA ; SELEX Aptamer Technique