The ability to navigate and understand the chemical literature is integral to the scientific research process. Learning these skills is therefore an important, though often overwhelming, part of an undergraduate chemical education. We describe an inquiry-based program designed to help chemistry students begin to learn to search and read the literature. The semester-long program is used within an honors general chemistry course but could be used during recitation sections of a larger general chemistry lecture course. It involves classroom and library tutorials and activities that introduce students to the skills necessary for utilizing today’s databases, online journals, and library resources. Over its 5-year existence, the program has been molded by student assessment, faculty feedback, and new developments in the field. The collaboration between and support by the chemistry and biochemistry department and the library were crucial to the success of the program. The program materials provided could easily be adapted to an online program or larger class with recitation sections.Keywords (Audience): First-Year Undergraduate/General; Keywords (Domain): Curriculum; Interdisciplinary/Multidisciplinary; Keywords (Pedagogy): Inquiry-Based/Discovery Learning; Keywords (Topic): Enrichment/Review Materials;

•Calcium aluminum oxide and hydroxyapatite were cast into a composite material.•Osteoblast attachment and proliferation were significantly increased on composites.•An active antimicrobial peptide was linked to and remained stable on the composite.•Bacterial turbidity and NPN uptake tests showed modified composites had an effect equal to a 10 μM Inverso-CysHHC10 solution.•Antimicrobial peptide linkage did not affect the increased osteoblast performance.A new composite bioceramic consisting of calcium aluminum oxide (CaAlO) and hydroxyapatite (HA) was functionalized with the synthetic antimicrobial peptide Inverso-CysHHC10. CaAlO is a bioceramic that can be mold cast easily and quickly at room temperature. Improved functionality was previously achieved through surface reactions. Here, composites containing 0–5% HA (by mass) were prepared and the elastic modulus and modulus of rupture were mechanically similar to non-load bearing bone. The addition of hydroxyapatite resulted in increased osteoblast attachment (> 180%) and proliferation (> 140%) on all composites compared to 100% CaAlO. Antimicrobial peptide (AMP) immobilization was achieved using an interfacial alkene-thiol click reaction. The linked AMP persisted on the composite (> 99.6% after 24 h) and retained its activity against Escherichia coli based on N-phenylnaphthylamine uptake and bacterial turbidity tests. Overall, this simple scaffold system improves osteoblast activity and reduces bacterial activity.

Stainless steel 316L (SS316L) is a common material used in orthopedic implants. Bacterial colonization of the surface and subsequent biofilm development can lead to refractory infection of the implant. Since the greatest risk of infection occurs perioperatively, strategies that reduce bacterial adhesion during this time are important. As a strategy to limit bacterial adhesion and biofilm formation on SS316L, self-assembled monolayers (SAMs) were used to modify the SS316L surface. SAMs with long alkyl chains terminated with hydrophobic (− CH3) or hydrophilic (oligoethylene glycol) tail groups were used to form coatings and in an orthogonal approach, SAMs were used to immobilize gentamicin or vancomycin on SS316L for the first time to form an “active” antimicrobial coating to inhibit early biofilm development. Modified SS316L surfaces were characterized using surface infrared spectroscopy, contact angles, MALDI-TOF mass spectrometry and atomic force microscopy. The ability of SAM-modified SS316L to retard biofilm development by Staphylococcus aureus was functionally tested using confocal scanning laser microscopy with COMSTAT image analysis, scanning electron microscopy and colony forming unit analysis. Neither hydrophobic nor hydrophilic SAMs reduced biofilm development. However, gentamicin-linked and vancomycin-linked SAMs significantly reduced S. aureus biofilm formation for up to 24 and 48 h, respectively.Highlights► SS316L was modified with glycol terminated SAMs in order to reduce biofilm growth. ► Antibiotics gentamicin and vancomycin were immobilized on SS316L via SAMs. ► Only the antibiotic modifications reduced biofilm development on SS316L.

Implant and medical device infection is a significant and potentially deadly problem in biomaterials today. In order to mitigate this issue vancomycin was either adsorbed or covalently attached to the calcium aluminum oxide surface and tested for antibacterial activity. Covalent attachment was accomplished by a three-step solution immobilization method utilizing the hydroxyl groups on the calcium aluminum oxide surface. The three-step covalent antibiotic attachment method is applicable to any surface that contains hydroxyl and μ-oxo groups. Antibacterial activity of the immobilized antibiotics was evaluated by incubating the unmodified oxide and modified samples in a liquid Staphylococcus aureus bacterial solution. Growth of the bacteria was determined by optical density. Additionally, bacterial growth was evaluated in a zone inhibition assay. It was found that unmodified samples, vancomycin adsorbed, and vancomycin linked to the surface inhibited bacterial growth in liquid culture. Vancomycin linked or adsorbed to the surface produced zones of inhibition equal to that of the control antibiotic disk indicating it is as active on the surface as the native antibiotic. These samples can be autoclaved for sterilization and retain bioactivity. This is the first report of an attachment method for antibiotics on oxide surfaces that uses mild conditions.

Perfluorocarbon thin films and polymer brushes were formed on stainless steel 316 L (SS316L) to control the surface properties of the metal oxide. Substrates modified with the films were characterized using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), contact angle analysis, atomic force microscopy (AFM), and cyclic voltammetry (CV). Perfluorooctadecanoic acid (PFOA) was used to form thin films by self-assembly on the surface of SS316L. Polypentafluorostyrene (PFS) polymer brushes were formed by surface-initiated polymerization using SAMs of 16-phosphonohexadecanoic acid (COOH-PA) as the base. PFOA and PFS were effective in significantly reducing the surface energy and thus the interfacial wetting properties of SS316L. The SS316L control exhibited a surface energy of 38 mN/m compared to PFOA and PFS modifications, which had surface energies of 22 and 24 mN/m, respectively. PFOA thin films were more effective in reducing the surface energy of the SS316L compared to PFS polymer brushes. This is attributed to the ordered PFOA film presenting aligned CF3 terminal groups. However, PFS polymer brushes were more effective in providing corrosion protection. These low-energy surfaces could be used to provide a hydrophobic barrier that inhibits the corrosion of the SS316L metal oxide surface.

Native oxide surfaces of stainless steel 316L and Nitinol alloys and their constituent metal oxides, namely nickel, chromium, molybdenum, manganese, iron, and titanium, were modified with long chain organic acids to better understand organic film formation. The adhesion and stability of films of octadecylphosphonic acid, octadecylhydroxamic acid, octadecylcarboxylic acid, and octadecylsulfonic acid on these substrates were examined in this study. The films formed on these surfaces were analyzed by diffuse reflectance infrared Fourier transform spectroscopy, contact angle goniometry, atomic force microscopy, and matrix-assisted laser desorption ionization mass spectrometry. The effect of the acidity of the organic moiety and substrate composition on the film characteristics and stability is discussed. Interestingly, on the alloy surfaces, the presence of less reactive metal sites does not inhibit film formation.

Self-assembled monolayer formation of alkylphosphonic acids on the native nickel oxide surface has been accomplished. These monolayers are the first formed on the native nickel oxide surface that did not require electrochemical reduction of the surface to metallic nickel. Two different deposition methods, immersion and aerosol spraying, were used to form monolayers on the oxide surface. Both methods led to complete monolayer formation, with the aerosol method requiring shorter deposition time, lower temperature and decreased solution concentration compared to the immersion method. These deposition methods now allow nickel oxide substrates to be functionalized easily. Monolayer formation was investigated by diffuse reflectance Fourier transform infrared spectroscopy, non-contact mode atomic force microscopy, contact angle measurements and matrix-assisted laser desorption ionization mass spectrometry. Furthermore, cyclic voltammetry and electrochemical impedance spectroscopy studies show that the monolayer increased surface resistance to oxidation.

A surface-initiated polymerization of styrene on carboxylic acid terminated phosphonic monolayers was utilized to increase the corrosion resistance of nitinol and nickel oxide surfaces. Alkyl chain ordering, organic reactions, wettability, and film quality of the monolayers and polymers were determined by infrared spectroscopy, atomic force microscopy, matrix-assisted laser desorption ionization spectrometry, and water contact angles. The polystyrene film proved to be a better corrosion barrier than phosphonic acid monolayers by analysis with cyclic voltammetry and electrochemical impedance spectroscopy. The protection efficiency of the polystyrene film on nitinol was 99.4% and the monolayer was 42%.

Aza-bis(oxazoline) copper complexes have been immobilized onto alkanethiol self-assembled monolayers on gold utilizing five background tail groups with different electronic characteristics. The catalyst was tested in the standard cyclopropanation reaction of ethyl diazoacetate and styrene. The five different tail groups were hydroxyl, bromine, carboxylic acid, ester, and nitrile. Enantioselectivity improved to 95% when the surrounding tail groups were hydroxyl- and bromine-terminated surfaces. The carboxylic acid and ester tail groups reduced the enantioselectivity compared to the homogeneous phase. Additionally, the homogeneous cyclopropanation reaction was performed in methanol, acetonitrile, ethyl acetate, and acetic acid to determine whether similar trends in selectivity could be obtained by varying the homogenous electronic environment. However, the cyclopropanation reaction in these solvents gave greatly reduced selectivity and yield of the cyclopropane products demonstrating the positive aspects of immobilization of self-assembled monolayer supports.Aza-bis(oxazoline) copper complex has been immobilized onto alkanethiol self-assembled monolayers utilizing five different background tail groups with different electronic characteristics.Download high-res image (46KB)Download full-size image

Aza-bis(oxazoline) copper complexes have been immobilized onto alkanethiol self-assembled monolayers with three different surface orientations and tested in the benchmark cyclopropanation reaction of ethyl diazoacetate and styrene. The three surface orientations were the catalyst backbone above, below, and even with the tail groups of the self-assembled monolayer. Enantioselectivity of the product improved to >90% by immobilization of the catalyst at the monolayer surface and was significantly reduced when the catalyst was imbedded in the monolayer. The catalyst presented above the monolayer surface is a solution mimic in terms of selectivity. The catalytic chips proved to be recyclable.Aza-bis(oxazoline) copper complexes have been immobilized onto alkanethiol self-assembled monolayer with three different surface orientations and tested in the benchmark cyclopropanation reaction of ethyl diazoacetate and styrene.Download high-res image (101KB)Download full-size image

•Thin film functionalized PLGA nanoparticles were modified to release nitric oxide from an s-nitrosothiol donor.•The nitric oxide modified nanoparticles were bacteriostatic against Escherichia coli.•The nitric oxide modified nanoparticles increased the effectiveness of tetracycline against Escherichia coli.•The modified nitric oxide nanoparticles did not exhibit cytotoxic effects against fibroblasts.Polymer nanoparticles consisting of poly (DL-lactic-co-glycolic acid) were surface functionalized to deliver nitric oxide. These biodegradable and biocompatible nanoparticles were modified with an S-nitrosothiol molecule, S-nitrosocysteamine, as the nitric oxide delivery molecule. S-nitrosocysteamine was covalently immobilized on the nanoparticle surface using small organic molecule linkers and carbodiimide coupling. Nanoparticle size, zeta potential, and morphology were determined using dynamic light scattering and scanning electron microscopy, respectively. Subsequent attachment of the S-nitrosothiol resulted in a nitric oxide release of 37.1 ± 1.1 nmol per milligram of nanoparticles under physiological conditions. This low concentration of nitric oxide reduced Escherichia coli culture growth by 31.8%, indicating that the nitric oxide donor was effective at releasing nitric oxide even after attachment to the nanoparticle surface. Combining the nitric oxide modified nanoparticles with tetracycline, a commonly prescribed antibiotic for E. coli infections, increased the effectiveness of the antibiotic by 87.8%, which allows for lower doses of antibiotics to be used in order to achieve the same effect. The functionalized nanoparticles were not cytotoxic to mouse fibroblasts.