Articles

News and Research

6

Jul

2017

Techconnect World Innovation Conference: May 2017

Computational Analysis of Electrical Stimulation Devices to Promote Wound Healing

Electric stimulation (ES) therapy involves the use of lower energy, static, or time-varying electric and magnetic fields and associated electrical currents to stimulate a therapeutic physiological response that accelerates wound healing in human tissue. In this presentation, we discuss this therapy and demonstrate the use of 3D computational models to predict the electric field and current density patterns induced in human tissue by voltage activated electrodes on the skin surface. The analysis takes into account electrode configurations, transient voltage waveforms and all relevant tissues including their frequency dependent electrical properties. The models provide insight into ES therapy and enable the rational design of novel ES devices.

20

Dec

2016

Cathodic voltage-controlled electrical stimulation of titanium for prevention of methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii biofilm infections

Mary Canty a, Nicole Luke-Marshall b, Anthony Campagnari b, Mark Ehrensberger a,c,⇑

Antibiotic resistance of bacterial biofilms limits available treatment methods for implant-associated orthopaedic infections. This study evaluated the effects of applying cathodic voltage-controlled electrical stimulations (CVCES) of 1.5 V and 1.8 V (vs. Ag/AgCl) to coupons of commercially pure titanium (cpTi) incubated in cultures of methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii (A. baumannii) as a method of preventing bacterial attachment. Stimulations were applied for 2, 4, and 8 h and coupon-associated and planktonic colony-forming units (CFU) were enumerated following stimulation. Compared to open circuit potential (OCP) controls, CVCES for 4 h at 1.8 V significantly reduced 4 7 coupon-associated MRSA CFU by 99.9% (1.30  107 vs. 4.45  10 , p = 0.047) and A. baumannii coupon4 associated CFU by 99.9% (1.64  10 vs. 5.93  10 , p = 0.001) and reduced planktonic CFU below detectable levels for both strains. CVCES at 1.8 V for 8 h also reduced coupon-associated and planktonic CFU below detectable levels for each strain. CVCES at 1.5 V for 4 and 8 h, and 1.8 V for 2 h did not result in clinically relevant reductions. For 4 and 8 h stimulations, the current density was significantly higher for 1.8 V than 1.5 V, an effect directly related to the rate of water and oxygen reduction on the cpTi surface. This significantly increased the pH, a suspected influence in decreased CFU viability. The voltagedependent electrochemical properties of cpTi likely contribute to the observed antimicrobial effects of CVCES. This study revealed that CVCES of titanium could prevent coupon-associated and planktonic CFU of Gram-positive MRSA and Gram-negative A. baumannii from reaching detectable levels in a magnitude-dependent and time-dependent manner.

14

Nov

2016

Cathodic voltage-controlled electrical stimulation of titanium implants as treatment for methicillin-resistant Staphylococcus aureus periprosthetic infections.

Ehrensberger MT1, Tobias ME2, Nodzo SR2, Hansen LA3, Luke-Marshall NR3, Cole RF2, Wild LM4, Campagnari AA3.

Abstract

Effective treatment options are often limited for implant-associated orthopedic infections. In this study we evaluated the antimicrobial effects of applying cathodic voltage-controlled electrical stimulation (CVCES) of -1.8 V (vs. Ag/AgCl) to commercially pure titanium (cpTi) substrates with preformed biofilm-like structures of methicillin-resistant Staphylococcus aureus (MRSA). The in vitro studies showed that as compared to the open circuit potential (OCP) conditions, CVCES of -1.8 V for 1 h significantly reduced the colony-forming units (CFU) of MRSA enumerated from the cpTi by 97% (1.89 × 106 vs 6.45 × 104 CFU/ml) and from the surrounding solution by 92% (6.63 × 105 vs. 5.15 × 104 CFU/ml). The in vivo studies, utilizing a rodent periprosthetic infection model, showed that as compared to the OCP conditions, CVCES at -1.8 V for 1 h significantly reduced MRSA CFUs in the bone tissue by 87% (1.15 × 105 vs. 1.48 × 104 CFU/ml) and reduced CFU on the cpTi implant by 98% (5.48 × 104 vs 1.16 × 103 CFU/ml). The stimulation was not associated with histological changes in the host tissue surrounding the implant. As compared to the OCP conditions, the -1.8 V stimulation significantly increased the interfacial capacitance (18.93 vs. 98.25 μF/cm(2)) and decreased polarization resistance (868,250 vs. 108 Ω-cm(2)) of the cpTi. The antimicrobial effects are thought to be associated with these voltage-dependent electrochemical surface properties of the cpTi. 

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