Convection-enhanced delivery (CED) is an advanced infusion technique used to deliver therapeutic agents into the brain. CED has shown promise in recent clinical trials. Independent verification of published parameters is warranted with benchmark testing of published parameters in applicable models such as gel phantoms, ex vivo tissue and in vivo non-human animal models to effectively inform planned and future clinical therapies. In the current study, specific performance characteristics of two CED infusion catheter systems, such as backflow, infusion cloud morphology, volume of distribution (mm(3)) versus the infused volume (mm(3)) (Vd/Vi) ratios, rate of infusion (µl min(-1)) and pressure (mmHg), were examined to ensure published performance standards for the ERG valve-tip (VT) catheter. We tested the hypothesis that the ERG VT catheter with an infusion protocol of a steady 1 µl min(-1) functionality is comparable to the newly FDA approved MRI Interventions Smart Flow (SF) catheter with the UCSF infusion protocol in an agarose gel model. In the gel phantom models, no significant difference was found in performance parameters between the VT and SF catheter. We report, for the first time, such benchmark characteristics in CED between these two otherwise similar single-end port VT with stylet and end-port non-stylet infusion systems. Results of the current study in agarose gel models suggest that the performance of the VT catheter is comparable to the SF catheter and warrants further investigation as a tool in the armamentarium of CED techniques for eventual clinical use and application.

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Background: Delivery of multiple collinear payloads utilizing convection-enhanced delivery (CED) has historically been performed by retraction of a needle or catheter from the most distal delivery site. Few studies have addressed end-infusion morphology and associated payload reflux in stacked and collinear infusions, and studies comparing the advancement with the retraction mode are lacking. Objective: To compare advancement versus retraction mode infusion results. Methods: Infusion cloud pairs were created with the advancement and retraction technique in agarose gel using both open end-port SmartFlow™ (SF) and valve tip (VT) catheter infusion systems. Backflow, radius of infusion, and morphology were assessed. Results: Infusions with the SF catheter, in contrast to the VT catheter, exhibited significantly more backflow in retraction mode at the shallow infusion site. Infusion morphology differed with the second infusion after retraction: the infusate at the proximal site first filling the channel left by the retraction and then being convected into gel in a pronouncedly non-spherical shape during the second infusion. Conclusions: Significant differences in cloud morphology were noted with respect to external catheter geometry with retraction versus penetration between infusions in an agarose gel model of the brain. Further study is warranted to determine optimal protocols for human clinical trials employing CED with multiple collinear payloads.

This paper critically reviews the current evidence of research in biomedical applications of selenium nanoparticles (SeNPs) and their effects at cellular and tissue levels. In recent years, interest in SeNPs as a natural trace element nanomaterial for nanomedicine has resulted in a number of studies evaluating their bioactivities, such as anticancer, antimicrobial, and antioxidant properties. Significant data have been generated to demonstrate the effectiveness of SeNPs alone or in combination with other reagents. Their activities are demonstrated through in vitro and in vivo experimentation; yet, the levels of efficacy need to be improved, particularly when compared with those of pharmaceutical drugs (such as antibiotics and cytotoxic chemotherapeutic drugs). However, promising evidence suggests decreased toxicity when using SeNPs, and more importantly their ability to perform as an interfacing biomaterial with cells and tissues. SeNPs have demonstrated unique antibacterial properties: they inhibit bacterial adhesion, growth, and/or quorum sensing and as a result prevent biofilm formation on medical devices, to name a few. Therefore, as with other nanomaterials, SeNPs warrant further study as part of the biomaterial-based therapeutic toolkit as an alternative to traditional pharmaceutical agents. This paper will provide a succinct review of recent studies on SeNPs to critically assess the findings in the light of effectiveness, particularly highlighting the roles of the cellular interface. Finally, an outlook of the potential of SeNPs will be presented to highlight the need for more intensive studies of material stability, mechanistic understanding at subcellular levels, and investigations into their combinational and/or synergistic effects with other bioactive reagents including pharmaceutical drugs.