The
growing global concerns to public health from human exposure
to perfluorooctanesulfonate (PFOS) require rapid, sensitive, in situ detection where current, state-of-the-art techniques
are yet to adequately meet sensitivity standards of the real world.
This work presents, for the first time, a synergistic approach for
the targeted affinity-based capture of PFOS using a porous sorbent
probe that enhances detection sensitivity by embedding it on a microfluidic
platform. This novel sorbent-containing platform functions as an electrochemical
sensor to directly measure PFOS concentration through a proportional
change in electrical current (increase in impedance). The extremely
high surface area and pore volume of mesoporous metal–organic
framework (MOF) Cr-MIL-101 is used as the probe for targeted PFOS
capture based on the affinity of the chromium center toward both the
fluorine tail groups as well as the sulfonate functionalities as demonstrated
by spectroscopic (NMR and XPS) and microscopic (TEM) studies. Answering
the need for an ultrasensitive PFOS detection technique, we are embedding
the MOF capture probes inside a microfluidic channel, sandwiched between
interdigitated microelectrodes (IDμE). The nanoporous geometry,
along with interdigitated microelectrodes, increases the signal-to-noise
ratio tremendously. Further, the ability of the capture probes to
interact with the PFOS at the molecular level and effectively transduce
that response electrochemically has allowed us achieve a significant
increase in sensitivity. The PFOS detection limit of 0.5 ng/L is unprecedented
for in situ analytical PFOS sensors and comparable
to quantification limits achieved using state-of-the-art ex
situ techniques.
Bacterial colonization and biofilm formation on an orthopedic implant surface is one of the worst possible outcomes of orthopedic intervention in terms of both patient prognosis and healthcare costs. Making the problem even more vexing is the fact that infections are often caused by events beyond the control of the operating surgeon and may manifest weeks to months after the initial surgery. Herein, we review the costs and consequences of implant infection as well as the methods of prevention and management. In particular, we focus on coatings and other forms of implant surface modification in a manner that imparts some antimicrobial benefit to the implant device. Such coatings can be classified generally based on their mode of action: surface adhesion prevention, bactericidal, antimicrobial-eluting, osseointegration promotion, and combinations of the above. Despite several advances in the efficacy of these antimicrobial methods, a remaining major challenge is ensuring retention of the antimicrobial activity over a period of months to years postoperation, an issue that has so far been inadequately addressed. Finally, we provide an overview of additional figures of merit that will determine whether a given antimicrobial surface modification warrants adoption for clinical use.
We present a straightforward, environmentally-benign, one-pot photochemical route to generate alloyed AgAu bimetallic nanoparticle decorated aminoclays in water at room temperature. The protocol uses no reducing agent (e.g., NaBH4) nor is photocatalyst required. These hybrid materials show excellent promise as dual catalysts/antibacterial agents.
BackgroundMultiple techniques exist for detecting Mycobacteria, each having its own advantages and drawbacks. Among them, automated culture-based systems like the BACTEC-MGIT™ are popular because they are inexpensive, reliable and highly accurate. However, they have a relatively long “time-to-detection” (TTD). Hence, a method that retains the reliability and low-cost of the MGIT system, while reducing TTD would be highly desirable.MethodsLiving bacterial cells possess a membrane potential, on account of which they store charge when subjected to an AC-field. This charge storage (bulk capacitance) can be estimated using impedance measurements at multiple frequencies. An increase in the number of living cells during culture is reflected in an increase in bulk capacitance, and this forms the basis of our detection. M. bovis BCG and M. smegmatis suspensions with differing initial loads are cultured in MGIT media supplemented with OADC and Middlebrook 7H9 media respectively, electrical “scans” taken at regular intervals and the bulk capacitance estimated from the scans. Bulk capacitance estimates at later time-points are statistically compared to the suspension’s baseline value. A statistically significant increase is assumed to indicate the presence of proliferating mycobacteria.ResultsOur TTDs were 60 and 36 h for M. bovis BCG and 20 and 9 h for M. smegmatis with initial loads of 1000 CFU/ml and 100,000 CFU/ml respectively. The corresponding TTDs for the commercial BACTEC MGIT 960 system were 131 and 84.6 h for M. bovis BCG and 41.7 and 12 h for M smegmatis, respectively.ConclusionOur culture-based detection method using multi-frequency impedance measurements is capable of detecting mycobacteria faster than current commercial systems.
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