Optimal tube length for the submerged printing of ovarian cancer cells.

Ovarian cancer is the fifth most common cancer affecting US women, killing more women each year than all other gynecologic cancers combined. Treatment of ovarian cancer is challenging with an overall 5-year survival rates of only 28-46% based on the metastatic state of the disease. While overall survival has improved with modern chemotherapy, poor outcomes have persisted. One of the greatest challenges in cancer therapeutic research remains that late-stage drug development trials for drug candidates have high attrition rates, up to 70% in Phase II and 59% in Phase III trials. The development of in vitro, high-throughput, cell based assays could provide a tool to overcome the challenges associated with high attrition rates by allowing for controlled cell deposition with a defined, controlled phenotype. Submerged, three-dimensional (3D) microfluidic printing technology is uniquely capable of controlling cell deposition without sacrificing the viability of cells for cell-based assays. Here, we investigate the phenotypic effects of tube length during printing on the cells. We observe that the length of the tube has minimal effects on the viability and density of A2780 ovarian cancer cells different cell lines. This study details foundational information for developing a high-throughput cell-based assays (CBA) for screening effective cancer drug candidates.

Comparison of submerged and unsubmerged printing of ovarian cancer cells.

A high-throughput cell based assay would greatly aid in the development and screening of ovarian cancer drug candidates. Previously, a three-dimensional microfluidic printer that is not only capable of controlling the location of cell deposition, but also of maintaining a liquid, nutrient rich environment to preserve cellular phenotype has been developed (Wasatch Microfluidics). In this study, we investigated the impact (i.e., viability, density, and phenotype) of depositing cells on a surface submerged in cell culture media. It was determined that submersion of the microfluidic print head in cell media did not alter the cell density, viability, or phenotype.. This article describes an in depth study detailing the impact of one of the fundamental components of a 3D microfluidic cell printer designed to mimic the in vivo cell environment. Development of such a tool holds promise as a high-throughput drug-screening platform for new cancer therapeutics.

Polymer-controlled extended combination release of silver and chlorhexidine from a bone void filler.

Although rates of total joint prosthetic infections remain relatively constant at 1-3%, an increasing number of orthopedic procedures and a corresponding rise in the absolute number of infectious complications mandate distinctly new solutions. In order to combat the implant infection threat, an antibiotic-releasing bone void filler (BVF), commercial tradename, ElutiBone™, has been developed using a combination of commercially available ceramic-based BVF plus clinically familiar biocompatible polymers, and a variety of select, dispersed antibiotics. While several traditional antibiotics have been successfully released for an extended duration, a more versatile strategy, releasing multiple antibiotics simultaneously, may be possible. In this study, the antiseptic chlorhexidine and a variety of bacteriostatic silver compounds were incorporated to provide synergistic antimicrobial activity upon release in combination formulations from ElutiBone matrices. Silver chloride was the most effective bacteriostatic tested (p=0.05), showing a measurable zone of inhibition at spiked concentrations as low as 31µg/ml. Subsequently, silver chloride was used in combination with the antiseptic chlorhexidine to test for enhanced antimicrobial bioactivity against S. aureus. Measurable synergy between the two compounds confirmed the suitability of ElutiBone™ to locally deliver this multidrug antimicrobial cocktail. A myriad of other drug interactions could and should be tested in this novel system in order to expand the utility and combat the increasing prevalence of polymicrobial infections.

The submerged printing of cells onto a modified surface using a continuous flow microspotter.

The printing of cells for microarray applications possesses significant challenges including the problem of maintaining physiologically relevant cell phenotype after printing, poor organization and distribution of desired cells, and the inability to deliver drugs and/or nutrients to targeted areas in the array. Our 3D microfluidic printing technology is uniquely capable of sealing and printing arrays of cells onto submerged surfaces in an automated and multiplexed manner. The design of the microfluidic cell array (MFCA) 3D fluidics enables the printhead tip to be lowered into a liquid-filled well or dish and compressed against a surface to form a seal. The soft silicone tip of the printhead behaves like a gasket and is able to form a reversible seal by applying pressure or backing away. Other cells printing technologies such as pin or ink-jet printers are unable to print in submerged applications. Submerged surface printing is essential to maintain phenotypes of cells and to monitor these cells on a surface without disturbing the material surface characteristics. By printing onto submerged surfaces, cell microarrays are produced that allow for drug screening and cytotoxicity assessment in a multitude of areas including cancer, diabetes, inflammation, infections, and cardiovascular disease.

Molded polymer-coated composite bone void filler improves tobramycin controlled release kinetics.

Infection remains a significant problem associated with biomedical implants and orthopedic surgeries, especially in revision total joint replacements. Recent advances in antibiotic-releasing bone void fillers (BVF) provide new opportunities to address these types of device-related orthopedic infections that often lead to substantial economic burdens and reduced quality of life. We report improvements made in fabrication and scalability of an antibiotic-releasing polycaprolactone-calcium carbonate/phosphate ceramic composite BVF using a new solvent-free, molten-cast fabrication process. This strategy provides the ability to tailor drug release kinetics from the BVF composite based on modifications of the inorganic substrate and/or the polymeric component, allowing extended tobramycin release at bactericidal concentrations. The mechanical properties of the new BVF composite are comparable to many reported BVFs and validate the relative homogeneity of fabrication. Most importantly, fabrication quality controls are correlated with favorable drug release kinetics, providing bactericidal activity to 10 weeks in vitro when the polycaprolactone component exceeds 98% w/w of the total polymer fraction. Furthermore, in a time kill study, tobramycin-releasing composite fragments inhibited S. aureus growth over 48 h at inoculums as high as 10(9) CFU/mL. This customizable antibiotic-releasing BVF polymer-inorganic biomaterial should provide osseointegrative and osteoconductive properties while contributing antimicrobial protection to orthopedic sites requiring the use of bone void fillers.

Scanning electron image analysis to monitor of implant degradation and host healing following implantation of a drug-eluting bone graft void filler - biomed 2013.

Osteomyelitis is most commonly caused by Staphylococcus aureus and often sourced during orthopedic surgical intervention. Successful treatment or prevention of this bone penetrating infection requires antibiotics be delivered in excess of the minimal inhibitory concentration to prohibit the growth of the causative organism for sufficient duration. Unfortunately, current standard-of-care antibiotic therapies, administered via intravenous or oral delivery, suffer not only from systemic toxicity and low patient compliance but also provide insufficient local concentrations for therapy. To overcome these clinical inadequacies, a synthetic bone graft material was coated with an antibiotic (tobramycin)-releasing polymer (polycaprolactone) matrix to create a polymer-controlled antibiotic- releasing combination therapy for use as a bone void filler in orthopedic surgeries. Even though this local delivery strategy allows antibiotic delivery over a clinically relevant time frame to prevent infection, complete healing requires the host bone to infiltrate and reabsorb the bone void filler, ultimately replacing the defect with healthy tissue. Unfortunately, the same polymer matrix that allows for controlled local antibiotic delivery may also discourage host bone healing. Efficient orthopedic healing requires the rate of polymer degradation to match the rate of host-bone infiltration. Current imaging techniques, such as histological staining and x-ray imaging, are insufficient to simultaneously assess polymer degradation and host bone integration. Alternative techniques relying on backscatter electron detection during scanning electron microscopy (SEM) imaging may allow a visual differentiation between host bone, synthetic bone, and polymer. Analysis of backscattered SEM images was automated using a custom MATLAB program to determine the ratio of bone to polymer based upon the contrast between the bone (white) and polymer (dark grey). By collecting images of the implant over time, a profile could be created to describe the rate of polymer degradation in conjunction with host-bone infiltration, allowing the intelligent tailoring of infectious osteomyelitis treatment/prevention and host-graft integration.

Polymer-controlled release of tobramycin from bone graft void filler.

Despite clinical, material, and pharmaceutical advances, infection remains a major obstacle in total joint revision surgery. Successful solutions must extend beyond bulk biomaterial and device modifications, integrating locally delivered pharmaceuticals and physiological cues at the implant site, or within large bone defects with prominent avascular spaces. One approach involves coating clinically familiar allograft bone with an antibiotic-releasing rate-controlling polymer membrane for use as a matrix for local drug release in bone. The kinetics of drug release from this system can be tailored via alterations in the substrate or the polymeric coating. Drug-loaded polycaprolactone coating releases bioactive tobramycin from both cadaveric-sourced cancellous allograft fragments and synthetic hybrid coralline ceramic bone graft fragments with similar kinetics over a clinically relevant 6-week timeframe. However, micron-sized allograft particulate provides extended bioactive tobramycin release. Addition of porogen polyethylene glycol to the polymer coating formulation changes tobramycin release kinetics without significant impact on released antibiotic bioactivity. Incorporation of oil-microencapsulated tobramycin into the polymer coating did not significantly modify tobramycin release kinetics. In addition to releasing inhibitory concentrations of tobramycin, antibiotic-loaded allograft bone provides recognized beneficial osteoconductive potential, attractive for decreasing orthopedic surgical infections with improved filling of dead space and new bone formation.

Evaluating antibiotic release profiles as a function of polymer coating formulation - biomed 2011.

To address persistent 1-3% infection rates associated with orthopedic implant surgeries, the next generation of bone graft filler materials will no longer pharmacologically silent being endowed as a local drug delivery vehicle to maintain locally high levels of antibiotic. Bone allograft material, used as a structural support to fill the avascular spaces in bone defects, revision surgeries, and traumatic injury, can be used as a drug depot to provide effective antibiotic delivery over the orthopedically relevant six-to-eight week time period. Passive antibiotic coatings, applied in the surgical theater, are quickly depleted from the site, inadvertently promoting the development of drug-resistance. Alternatively, many promising controlled-delivery strategies provide an initial burst release of antibiotic within 24 to 72 hours; however, this remains inadequate to combat the onslaught of ubiquitous pathogens that can persist only to reemerge once drug concentrations fall below the minimal inhibitory concentration (MIC). To improve the longevity of this strategy, a variety of coating techniques were evaluated in which clinically-accepted, FDA-recognized, degradable polycaprolactone (PCL) polymer acts as a rate-controlling membrane to retard the release of the antibiotic tobramycin from allograft bone. Using a combination of dipping and rapid drying, the drug-releasing polymer coating was applied concurrently maintaining the high surface area of the allograft bone; however, SEM imaging reveled an imperfect coating that negatively affected the release kinetics. Altering the drug-containing polymer formulation to incorporate water provided a smoother, more uniform coat and ultimately improved the drug-release profile and longevity out to 5 weeks using both bacteriostatic and bacteriocidal assays. Additionally, drug bioactivity was assessed and confirmed between 2 and 4 weeks in the absence of the water-containing polymer.

A robust method to coat allograft bone with a drug-releasing polymer shell - biomed 2010.

Bone allograft material used for osseous void filling and structural support in skeletal reconstructive surgeries can also be used in combination as a drug carrier. Previous coating methods to load drugs, such as antibiotics and anti-inflammatories, provided an initial burst release, which may not be optimal for combating persistent local implant-associated bacterial infections. Theoretical drug release kinetics can be optimized not only with a clinically relevant drug-to-polymer ratio but also with a robust, effective rate-limiting release coating method. Three coating methods were evaluated in which degradable polycaprolactone (PCL) polymer retains and controls the release of antibiotic tobramycin from commercial, clinically common allograft bone fragments. Methods are based on a common dip-coating of the allograft fragment, with each coating method distinguished by subsequent drying and processing steps. Using a combination of classic polymer coating techniques, dipping and rapid drying, a method has been developed to apply the drug-releasing polymer coating while concurrently maintaining the high surface area, cancellous pore allograft structure. This provides increased local drug loading and controlled release over the clinically relevant six-to-eight week time period. This method offers potential for industrial scale-up as multiple cancellous allograft fragments can be processed batch-wise. Multiple drugs and combination therapies can also be applied in laminate coating designs.