Antibacterial Activity of Electrospun Polyacrylonitrile Copper Nanoparticle Nanofibers on Antibiotic Resistant Pathogens and Methicillin Resistant Staphylococcus aureus (MRSA).

Bacteria induced diseases such as community-acquired pneumonia (CAP) are easily transmitted through respiratory droplets expelled from a person's nose or mouth. It has become increasingly important for researchers to discover materials that can be implemented in in vitro surface contact settings which disrupt bacterial growth and transmission. Copper (Cu) is known to have antibacterial properties and have been used in medical applications. This study investigates the antibacterial properties of polyacrylonitrile (PAN) based nanofibers coated with different concentrations of copper nanoparticles (CuNPs). Different concentrations of copper sulfate (CuSO4) and polyacrylonitrile (PAN) were mixed with dimethylformamide (DMF) solution, an electrospinning solvent that also acts as a reducing agent for CuSO4, which forms CuNPs and Cu ions. The resulting colloidal solutions were electrospun into nanofibers, which were then characterized using various analysis techniques. Methicillin-Resistant isolates of Staphylococcus aureus, an infective strain that induces pneumonia, were incubated with cutouts of various nanocomposites using disk diffusion methods on Luria-Bertani (LB) agar to test for the polymers' antibacterial properties. Herein, we disclose that PAN-CuNP nanofibers have successfully demonstrated antibacterial activity against bacteria that were otherwise resistant to highly effective antibiotics. Our findings reveal that PAN-CuNP nanofibers have the potential to be used on contact surfaces that are at risk of contracting bacterial infections, such as masks, in vivo implants, or surgical intubation.

Electrospun Polyacrylonitrile Silver(I,III) Oxide Nanoparticle Nanocomposites as Alternative Antimicrobial Materials.

Infectious microbial diseases can easily be transferred from person to person in the air or via high contact surfaces. As a result, researchers must aspire to create materials that can be implemented in surface contact applications to disrupt pathogen growth and transmission. This study examines the antimicrobial properties of polyacrylonitrile (PAN) nanofibers coated with silver nanoparticles (AgNPs) and silver(I,III) oxide. PAN was homogenized with varied weight concentrations of silver nitrate (AgNO3) in N,N-dimethylformamide solution, a common organic solvent that serves as both an electrospinning solvent and as a reducing agent that forms AgNPs. The subsequent colloids were electrospun into nanofibers, which were then characterized via various analysis techniques, including scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis, dynamic light scattering, and X-ray photoelectron spectroscopy. A total of 10 microbes, including 7 strains of Gram-positive bacteria, 2 strains of Gram-negative bacteria, and Candida albicans, were incubated with cutouts of various PAN-AgNP nanocomposites using disk diffusion methods to test for the nanocomposites' antimicrobial efficiency. We report that our electrospun PAN-AgNP nanocomposites contain 100% AgO, a rare, mixed oxidation state of silver(I,III) oxide that is a better sterilizing agent than conventional nanosilver. PAN-AgNP nanocomposites also retain a certain degree of antimicrobial longevity; samples stored for approximately 90 days demonstrate a similar antimicrobial activity against Escherichia coli (E. coli) and Lactobacillus crispatus (L. crispatus) when compared to their newly electrospun counterparts. Moreover, our results indicate that PAN-AgNP nanocomposites successfully display antimicrobial activity against various bacteria and fungi strains regardless of their resistance to conventional antibiotics. Our study demonstrates that PAN-AgNP nanocomposites, a novel polymer material with long-term universal antimicrobial stability, can potentially be applied as a universal antimicrobial on surfaces at risk of contracting microbial infections and alleviate issues related to antibiotic overuse and microbial mutability.

Conjugation of Carboxylated Graphene Quantum Dots with Cecropin P1 for Bacterial Biosensing Applications.

Biosensors that can accurately and rapidly detect bacterial concentrations in solution are important for potential applications such as assessing drinking water safety. Meanwhile, quantum dots have proven to be strong candidates for biosensing applications in recent years because of their strong light emission properties and their ability to be modified with a variety of functional groups for the detection of different analytes. Here, we investigate the use of conjugated carboxylated graphene quantum dots (CGQDs) for the detection of Escherichia coli using a biosensing assay that focuses on measuring changes in fluorescence intensity. We have further developed this assay into a novel, compact, field-deployable biosensor focused on rapidly measuring changes in absorbance to determine E. coli concentrations. Our CGQDs were conjugated with cecropin P1, a naturally produced antibacterial peptide that facilitates the attachment of CGQDs to E. coli cells; to our knowledge, this is the first instance of cecropin P1 being used as a biorecognition element for quantum dot biosensors. As such, we confirm the structural modification of these conjugated CGQDs in addition to analyzing their optical characteristics. Our findings have the potential to be used in situations where rapid, reliable detection of bacteria in liquids, such as drinking water, is required, especially given the low range of E. coli concentrations (103 to 106 CFU/mL) within which our two biosensing assays have collectively been shown to function.

Syntheses, crystallographic/computational characterizations, and reactions of the first 10-vertex arachno- and nido-phosphamonocarbaboranes.

A synthetic sequence involving the initial reaction of a substituted phosphorus dihalide (RPCl(2), R = CH(3), C(6)H(5)) with the arachno-CB(8)H(13)(-) (1-) monoanion followed by an in situ dehydrohalogenation reaction initiated by Proton Sponge, resulted in phosphorus cage insertion to yield the first 10-vertex arachno- and nido-phosphamonocarbaboranes, exo-6-R-arachno-6,7-PCB(8)H(12) (2a, 2b) and PSH(+)6-R-nido-6,9-PCB(8)H(9)(-) (PSH+3a-, PSH+3b-) (R = C(6)H(5) (a), CH(3) (b)). Alternatively, 2a and 2b were synthesized in high yield as the sole product of the reaction of the arachno-4-CB(8)H(12)(2-) (1(2-)) dianion with RPCl(2). Crystallographic determinations of PSH+3a- and PSH+3b- in conjunction with DFT/GIAO computational studies of the anions have confirmed the expected nido cage framework based on an octadecahedron missing the six-coordinate vertex. DFT/GIAO computational studies have also shown that while the gross cage geometries of the exo-6-R-arachno-6,7-PCB(8)H(12) compounds 2a and 2b resemble the known isoelectronic arachno-6,9-SCB(8)H(12), the phosphorus and carbon atoms are in thermodynamically unfavorable adjacent positions on the six-membered puckered face. They also each have an endo-hydrogen at the P6-position arising from proton transfer to the basic phosphorus during the cage-insertion reaction. Possible stepwise reaction pathways that can account for the formation of both the arachno and nido products are discussed. Deprotonation of 2a and 2b resulted in the formation of their corresponding conjugate monoanions, 6-R-arachno-6,7-PCB(8)H(11)(-) (2a-, 2b-), in which the proton that had been attached to the P6 atom was removed. Reactions of 2a- with O(2), S(8), BH(3).THF, or Br(2) further demonstrated the basicity of the P6-phosphorus yielding the new arachno-substituted compounds, endo-6-O-exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11)(-) (4a-), endo-6-S-exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11)(-) (5a-), endo-6-BH(3)-exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11)(-) (6a-), and endo-6-Br-exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11) (7a), respectively, in which the O, S, BH(3), and Br substituents are bound to the phosphorus at the endo position.