Effect of acid-alkali treatment on serum protein adsorption and bacterial adhesion to porous titanium.

Modification of the titanium (Ti) surface is widely known to influence biological reactions such as protein adsorption and bacterial adhesion in vivo, ultimately controlling osseointegration. In this study, we sought to investigate the correlation of protein adsorption and bacterial adhesion with the nanoporous structure of acid-alkali-treated Ti implants, shedding light on the modification of Ti implants to promote osseointegration. We fabricated nontreated porous Ti (NTPT) by powder metallurgy and immersed it in mixed acids and NaOH to obtain acid-alkali-treated porous Ti (AAPT). Nontreated dense sample (NTDT) served as control. Our results showed that nanopores were formed after acid-alkali treatment. AAPT showed a higher specific surface area and became much more hydrophilic than NTPT and NTDT (p < 0.001). Compared to dense samples, porous samples exhibited a lower zeta potential and higher adsorbed protein level at each time point within 120 min (p < 0.001). AAPT formed a thicker protein layer by serum precoating than NTPT and NTDT (p < 0.001). The main adsorbed proteins on AAPT and NTPT were albumin, α1 antitrypsin, transferrin, apolipoprotein A1, complement C3 and haptoglobin α1 chain. The amounts of bacteria adhering to the serum-precoated samples were lower than those adhering to the nonprecoated samples (p < 0.05). Lower-molecular-weight proteins showed higher affinity to porous Ti. In conclusion, acid-alkali treatment facilitated protein adsorption by porous Ti, and the protein coating tended to prevent bacteria from adhering. These findings may be utilized for Ti implant modification aimed at reducing bacterial adhesion and enhancing osseointegration. Graphical abstract.

Expression of anti-Müllerian hormone in two rat models of polycystic ovary syndrome.

AIM: Anti-Müllerian hormone (AMH) levels are two to three times higher in patients with polycystic ovary syndrome (PCOS), but the mechanism of increased AMH levels in PCOS remains unclear. The purpose of our experiment was to investigate a change in AMH levels in two kinds of commonly used rat models and to determine an ideal model for future research of AMH in the pathogenesis of PCOS. METHODS: Thirty female Sprague Dawley rats were treated using two modeling methods: implantation of a levonorgestrel silastic implant or injection with sodium prasterone sulfate plus human chorionic gonadotropin (hCG). Rats in the control group were implanted with a blank silastic stick. Serum steroid concentrations, ovarian morphology and ovarian expression of AMH and AMH-receptor II (RII) proteins were determined and their correlations were studied. RESULTS: The results from the levonorgestrel and hCG group were closer to those displayed by human PCOS patients than the sodium prasterone sulfate and hCG group. Ovarian local expression of AMH and AMH-RII was increased in these both models compared with the control group; however, an elevation of serum AMH concentration was not observed (12.53 ± 0.99 ng/ml and 13.22 ± 1.09 ng/ml vs 16.30 ± 0.98 ng/ml). CONCLUSION: The levonorgestrel and hCG model is more suitable for the study of PCOS in puberty.

Investigating ligand-receptor interactions at bilayer surface using electronic absorption spectroscopy and fluorescence resonance energy transfer.

We investigate interactions between receptors and ligands at bilayer surface of polydiacetylene (PDA) liposomal nanoparticles using changes in electronic absorption spectroscopy and fluorescence resonance energy transfer (FRET). We study the effect of mode of linkage (covalent versus noncovalent) between the receptor and liposome bilayer. We also examine the effect of size-dependent interactions between liposome and analyte through electronic absorption and FRET responses. Glucose (receptor) molecules were either covalently or noncovalently attached at the bilayer of nanoparticles, and they provided selectivity for molecular interactions between glucose and glycoprotein ligands of E. coli. These interactions induced stress on conjugated PDA chain which resulted in changes (blue to red) in the absorption spectrum of PDA. The changes in electronic absorbance also led to changes in FRET efficiency between conjugated PDA chains (acceptor) and fluorophores (Sulphorhodamine-101) (donor) attached to the bilayer surface. Interestingly, we did not find significant differences in UV-vis and FRET responses for covalently and noncovalently bound glucose to liposomes following their interactions with E. coli. We attributed these results to close proximity of glucose receptor molecules to the liposome bilayer surface such that induced stress were similar in both the cases. We also found that PDA emission from direct excitation mechanism was ~2-10 times larger than that of the FRET-based response. These differences in emission signals were attributed to three major reasons: nonspecific interactions between E. coli and liposomes, size differences between analyte and liposomes, and a much higher PDA concentration with respect to sulforhodamine (SR-101). We have proposed a model to explain our experimental observations. Our fundamental studies reported here will help in enhancing our knowledge regarding interactions involved between soft particles at molecular levels.

ABC Triblock Copolymers Antibacterial Materials Consisting of Fluoropolymer and Polyethylene Glycol Antifouling Block and Quaternary Ammonium Salt Sterilization Block.

Due to their various applications in human healthcare and industrial fields, engineering surfaces with antiadhesion and antibacteria properties is still a challenging task. In this work, the fluoropolymer with low surface energy and poly(poly(ethylene glycol) methyl ether methacrylate) (PEGMA) with electrostatic repulsion and interfacial hydration was chosen as a common antiadhesion block and quaternary ammonium salt with bactericide properties as a sterilization block. The triblock copolymers of poly(2-(dimethylamino)ethyl methacrylate)-b-poly(poly(oligo ethylene glycol) methyl ether methacrylate)-b-poly(dodecafluoroheptyl methacrylate) (PDMAEMA-b-PEGMA-b-PDFHMA) were synthesized by the reversible addition-fragmentation chain transfer (RAFT) polymerization method. Then, the synthesized triblock copolymers were quaternized to obtain the antibacterial materials (QPDMAEMA-b-PEGMA-b-PDFHMA). It has been found that the QPDMAEMA-b-PEGMA-b-PDFHMA triblock copolymer coating has excellent antiadhesion and antibacterial properties against S. aureus and E. coli. The synergistic effects of fluoropolymer and PEGMA can enhance the antifouling properties of the coating. At the same time, it has a good antifouling effect on platelets and red blood cells. In addition, the triblock copolymer coating has long-term stability in high ionic strength solution of PBS in dynamic conditions. These kind of materials with antifouling and antibacterial properties may have potential applications on the surface of various public utilities and medical equipment.

Multifunctional Antibacterial Materials Comprising Water Dispersible Random Copolymers Containing a Fluorinated Block and Their Application in Catheters.

Inhibiting the attachment of bacteria and the formation of biofilms on surfaces of materials and devices is the key to ensure public safety and is also the focus of attention and research. Here we report on the synthesis of multifunctional antibacterial materials based on water dispersible random copolymers containing a fluorinated block, poly(acrylic acid-co-1H,1H,2H,2H-perfluorododecyl acrylate) (PAA-co-PFDA), and poly(hexamethylene biguanide) hydrochloride (PHMB). PAA-co-PFDA copolymers were synthesized through a simple free radical polymerization. After lightly cross-linking of PAA-co-PFDA and complexation with PHMB, multifunctional antibacterial PAA-co-PFDA/PHMB complex nanoparticles were generated, which can form transparent coatings on various substrates. The resultant coating has aggregation-induced emission character which can be used to observe the uniformity of the coating on a catheter and has a potential application as a fluorescence probe. It has been demonstrated that the PAA-co-PFDA/PHMB complex nanoparticle coatings can resist bacterial adhesion in physiological environment and exhibit excellent antibacterial activity in infection environment. In vitro and in vivo experiments indicated that the PAA-co-PFDA/PHMB complex nanoparticle coated catheters exhibited excellent antibacterial activity and possessed good biocompatibility. This method is simple and scalable, which is important for future commercialization. The attractive multifunctional properties of the PAA-co-PFDA/PHMB complex nanoparticles, such as antifouling, antimicrobial, emission, and pH-responsive release character, have great potential application in a wide range of biomedical fields.

Fluorescence resonance energy transfer in polydiacetylene liposomes.

Conjugated polydiacetylene (PDA) possessing stimuli-responsive properties has been intensively investigated for developing efficient sensors. We report here fluorescence resonance energy transfer (FRET) in liposomes synthesized using different molar ratios of dansyl-tagged diacetylene and diacetylene-carboxylic acid monomers. Photopolymerization of diacetylene resulted in cross-linked PDA liposomes. We used steady-state electronic absorption, emission, and fluorescence anisotropy (FA) analysis to characterize the thermal-induced FRET between dansyl fluorophores (donor) and PDA (acceptor). We found that the monomer ratio of acceptor to donor ( R ad) and length of linkers (functional part that connects dansyl fluorophores to the diacetylene group in the monomer) strongly affected FRET. For R ad = 10 000, the acceptor emission intensity was amplified by more than 18 times when the liposome solution was heated from 298 to 338 K. A decrease in R ad resulted in diminished acceptor emission amplification. This was primarily attributed to lower FRET efficiency between donors and acceptors and a higher background signal. We also found that the FRET amplification of PDA emissions after heating the solution was much higher when dansyl was linked to diacetylene through longer and flexible linkers than through shorter linkers. We attributed this to insertion of dansyl in the bilayer of the liposomes, which led to an increased dansyl quantum yield and a higher interaction of multiple acceptors with limited available donors. This was not the case for shorter and more rigid linkers where PDA amplification was much smaller. The present studies aim at enhancing our understanding of FRET between fluorophores and PDA-based conjugated liposomes. Furthermore, receptor tagged onto PDA liposomes can interact with ligands present on proteins, enzymes, and cells, which will produce emission sensing signal. Therefore, using the present approach, there exist opportunities for designing FRET-based highly sensitive and selective chemical and biochemical sensors.

A mediator-free amperometric hydrogen peroxide biosensor based on HRP immobilized on a nano-Au/poly 2,6-pyridinediamine-coated electrode.

A mediator-free amperometric hydrogen peroxide biosensor was prepared by immobilizing horseradish peroxidase (HRP) enzyme on colloidal Au modified platinum (Pt) wire electrode, which was modified by poly 2,6-pyridinediamine (pPA). The modified process was characterized by electrochemical impedance spectroscopy (EIS), and the electrochemical characteristics of the biosensor were studied by cyclic voltammetry, linear sweep voltammetry and chronoamperometry. The biosensor displayed an excellent electrocatalytical response to reduction of H(2)O(2) without the aid of an electron mediator, the linear range was 4.2 x 10(-7)-1.5 x 10(-3) mol/L (r = 0.9977), with a detection limit of 1.4 x 10(-7) mol/L. Moreover, the performance and factors influencing the resulted biosensor were studied in detail. The studied biosensor exhibited permselectivity, good stability and good fabrication reproducibility.