ABSTRACT
Polymer self-healing is mainly based on the molecular structure and interaction of polymers, and some need external stimulation, such as light, heat, pH, etc. In recent years, many studies have found that the self-healing properties of polymers can prolong the life of materials, while maintaining the mechanical properties of polymers after healing. According to the different action modes of polymer materials, it can be divided into autonomous self-healing and non-autonomous self-healing. Among them, autonomous self-healing mainly works through reversible covalent bonds (Schiff base bond, Diels-Alder reaction, hydrazide bond), reversible non-covalent bonds (hydrogen bond, metal-ligand coordination bond, electrostatic interaction, π-π stacking interaction, hydrophobic interaction) and a combination of the two interactions. Drug carriers with unique self-healing properties play an important role in the encapsulation and stable release of biomacromolecules. In this review, the self-healing mechanism of polymers and their applications in the field of biomedicine were briefly summarized and discussed.
ABSTRACT
The non-covalent interactions between 18-crown-6 (18c6) and 20 common types of protonated amino acids were explored by electrospray ionization mass spectrometry (ESI-MS).The mass spectra showed the formation of 1:1 stoichiometric non-covalent complexes between 18c6 and amino acids.The calibration curves and linear equations for the complexes of L-Phe,L-Tyr,L-Lys and L-Asp with 18c6 were established by mass spectrometric titration and used as reference values for competitive ESI-MS.Through competitive equilibrium,the binding constants for the complexes of 18c6 with other L-amino acids and their D-isomers were derived.It was found,as a general trend,lgKa for the complexes of 18c6 with the basic amino acid and the amino acid with alkyl side chain were larger than other complexes,and among the amino acids with alkyl side chain,Gly and Ala exhibited greater 18c6 binding affinities.As for Ser and Thr,the intramolecular hydrogen bond between the nitrogen atom from terminal NH2and the oxygen atom from carboxyl may impede their protonated amino-group to attack the 18c6.Furthermore,Gln and Asn exhibited lower 18c6 binding affinities probably due to effects of electron-withdrawing group of acylamide.Finally,the chiral selectivity of 18c6 for 19 L-,or D-amino acids was measured by ESI-MS,indicating 18c6 could only recognize some neutral amino acid isomers.
ABSTRACT
The diffusion coefficient ((4. 11±0. 78)×10-11 m2/s) and hydrated radius ((6. 12±1. 21) nm) of FITC-DSA ( fluorescein isothiocyanate conjugate dog albumin ) were investigated and measured by combining Taylor dispersion analysis with laser induced fluorescence in microchip. The influence of size of gold nanoparticles (15, 30 and 50 nm) on the interactions between FITC-DSA and gold nanoparticles was studied. The preliminary result demonstrated that the binding of protein and gold nanoparticle displayed a size-dependent relationship. It was interesting that the 50-nm gold nanoparticles could enhance the FITC-DSA fluorescence in microchannel driven with pressure. This method was simple, fast, low sample consumption and high throughput and could be used to study the interaction of nanoparticles and proteins. Systematical study using this method would enable us to have a deep understanding of the toxicity of nanomaterials, and promote the development of safe nanomedicine.
ABSTRACT
Several delivery systems are developed to target methotrexate to cancer tissues with limited success due to low drug loading, size control, toxicity, and scale up and also the cost of formulation. Off late, carbon nanotubes have been projected as a promising carrier for many drugs including anticancer agents. The present work is an attempt to investigate the potentialities of multi-walled carbon nanotubes (MWCNT) as a carrier for targeting methotrexate to cancer tissues. MWCNTs were functionalized using DSPE-mPEG 2000 and was then reacted with methotrexate (MTX) to produce MWCNT-mPEG-MTX conjugate. The conjugate was characterized for particle size, loading efficiency, morphology & rate of drug release. The result indicated that about 2.26 mg of Methotrexate per mg of MWCNTs were loaded with 56.5% entrapment efficiency. Particle size of the MWCNT conjugate was found to be less than 200nm with polydispersity index of 0.286 post lyophilization of the product. The MWCNT conjugate was found to release the drug faster in acidic medium than at neutral pH. However, in both neutral and acidic media, the release was continuous over the period of 48 hours.