Cyclic High Negative-Pressure External Volume Expansion Reduces Daily Device Application Time With Similar Effects on Recipient Site Preparation in a Murine Model.

Introduction: Recipient site preparation using external volume expansion (EVE) increases graft survival in large-volume fat grafting. To improve patient compliance with using the device, we tested a new cyclic high negative-pressure (CHNP) mode that involves 1 h/day at -55 mm Hg, cycled between 1-second negative-pressure activation, followed by a 2-second deactivation period in an animal model. Material and Method: A miniaturized EVE device was applied to 30 8-week-old male Sprague-Dawley rats. The rats were assigned to 3 groups (no pressure for the control group, conventional -25 mm Hg for 8 h/day for conventional EVE, and CHNP mode for the CHNP group). After 28 days, micro-computed tomography was performed and skin biopsy specimens were obtained. Results: The CHNP group showed a 6.6-fold increase and the conventional EVE group showed a 4.4-fold increase in volume compared to the control group. Hematoxylin and eosin staining showed a similar increase in subcutaneous tissue thickness in both EVE groups, compared to the control group. Masson's trichome and proliferating cell nuclear antigen staining showed significantly higher collagen deposition and subdermal adipocytes in EVE groups. Immunohistochemistry against platelet endothelial cell adhesion molecule 1 showed 2.5- and 2.7-times higher vessel density in the conventional and CHNP EVE groups, respectively. There was no statistically significant difference in subcutaneous tissue thickness, collagen deposition, subdermal adipocyte proliferation, and vessel density between the 2 EVE groups. Conclusion: CHNP produced comparable results in recipient site preparation (subcutaneous tissue thickening and angiogenesis) compared to the conventional protocol, while markedly reducing the daily wear-time from 8 hours to 1 hour. Although further clinical data must be acquired, our new pressure setting seems promising and provides a more patient-friendly pre-expansion environment.

Introduction: La préparation du site receveur utilisant l'expansion de volume externe (EVE) augmente la survie d'une greffe dans une greffe de tissu adipeux de grand volume. Pour améliorer l'observance de l'utilisation du dispositif par le patient, nous avons testé un nouveau mode cyclique à forte pression négative (CHNP) qui implique 1 heure par jour à −55 mm Hg, dans un cycle entre une activation de pression négative 1-s suivie d'une période de désactivation de 2-s dans un modèle animal. Matériel et Méthode: Un dispositif EVE miniaturisé a été appliqué à 30 rats mâles Sprague-Dawley âgés de 8 semaines. Les rats ont été répartis en trois groupes (pas de pression dans le groupe témoin, pression conventionnelle de −25 mm Hg pendant 8 h/jour pour l'EVE conventionnelle et forte pression cyclique négative pour le groupe CHNP). Après 28 jours, une micro-tomodensitométrie (TDM) a été réalisée et des échantillons de biopsie de peau ont été prélevés. Résultats: Le groupe CHNP avait une augmentation de 6,6 fois, et le groupe d'EVE conventionnelle présentait une augmentation de 4,4 fois le volume comparativement au groupe contrôle. La coloration à l'hématoxyline-éosine a mis en évidence une augmentation similaire de l'épaisseur du tissu sous-cutané dans les 2 groupes EVE, par rapport au groupe contrôle. Le trichrome de Masson et la coloration pour l'antigène nucléaire de prolifération cellulaire (PCNA) ont montré un dépôt de collagène significativement plus important et des adipocytes sous-dermiques plus nombreux dans les groupes EVE. L'immunohistochimie contre les molécules d'adhésion-1 des cellules endothéliales d'origine plaquettaire a montré une densité vasculaire plus élevée de 2,5 fois et 2,7 fois dans, respectivement, les groupes EVE conventionnelle et EVE CHNP. Il n'y a pas eu de différence statistiquement significative concernant l'épaisseur du tissu sous-cutané, le dépôt de collagène, la prolifération des adipocytes sous-dermiques et la densité des vaisseaux sanguins entre les deux groupes EVE. Conclusion: La forte pression négative cyclique a obtenu des résultats comparables pour la préparation d'un site receveur (épaississement du tissu sous-cutané et angiogenèse) comparativement au protocole conventionnel, tout en ayant une durée de port quotidien nettement réduite de 8 heures à 1 heure. Des données cliniques supplémentaires doivent être obtenues, mais notre nouveau cadre de pression semble prometteur et offre un environnement préexpansion plus agréable pour le patient.

Author Correction: Noninvasive Self-diagnostic Device for Tear Collection and Glucose Measurement.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Wirelessly Controlled Implantable System for On-demand and Pulsatile Insulin Administration.

We propose a wirelessly controlled implantable system for on-demand and pulsatile insulin delivery with a more convenient and safer strategy than currently available strategies. The system is a combined entity of a magnetically driven pump (i.e., an MDP), external control device (i.e., an ECD) and mobile app. The MDP for implantation consists of a plunger, barrel and drug reservoir, where an accurate amount of insulin can be infused in a pulsatile manner only at the time when a magnetic force is applied to actuate the plunger in the barrel. The ECD at the outside body can modulate the MDP actuation with an electromagnet and its control circuit, and this modulation can be wirelessly controlled by the mobile app. As a safety feature, the mobile app is programmed to pre-set the restrictions for the insulin dose and administration schedule to avoid overdose. The system is shown to infuse insulin in a highly reproducible manner, but it does not allow for insulin infusion when the pre-set restrictions are violated. When tested with diabetic rats, the profiles of insulin plasma concentration and blood glucose level are similar to those of animals treated with a subcutaneous injection of the same dose of insulin.

Noninvasive Self-diagnostic Device for Tear Collection and Glucose Measurement.

We propose a noninvasive, self-diagnostic device that enables safe tear collection and glucose measurement. The device described herein was manufactured by tight assembly of a lid for tear collection in conjunction with a strip-type glucose sensor. The lid was designed to be in contact with the inferior palpebral conjunctiva for tear collection and was thus designed to possess a proper contact area and rounded boundaries to avoid eye tissue damage. For the strip-type glucose sensor, we employed a commercially available electrochemical sensor (Accu-Chek test strips), which was modified to reduce the volume of the reaction chamber (0.4 µl) for a small amount of collected tear fluid. When tested with in vivo animal models, the device was able to collect tear fluid in a relatively short time (<2 s) without causing eye tissue damage, and the device allowed the collected tear fluid to be delivered to the sensor for measurement of tear glucose concentrations. The blood glucose concentrations estimated with the tear glucose concentrations obtained with the device exhibited a high correlation with those actually measured with a clinically available glucometer (R2 = 0.9617).

Mucoadhesive Microparticles Engineered for Ophthalmic Drug Delivery.

Although topical drug delivery is a convenient route of administration to treat various eye diseases, it has serious limitations due to rapid clearance of the formulation from the surface of the eye. In this study, we engineered microparticles for both sustained drug delivery and prolonged residence time on the extraocular surface. Microparticles were fabricated by emulsification using poly(lactic-co-glycolic acid) (PLG) and poly(ethylene glycol) (PEG) as the core material and mucoadhesion promoter, respectively. The particle size was controlled to be less than 10 microm to avoid eye irritation and for eventual clearance through the lacrimal canals. In vitro mucoadhesion tests showed that PLG microparticles with PEG adhered better to the mucous membrane under the conditions employed in this study compared to the microparticles without PEG. When an aqueous suspension of microparticles with PEG was administered topically to the rabbit eye in vivo, microparticles were seen for up to 30 min on the ocular surface in the cul-de-sac, which was a dramatic increase in residence time as compared to conventional eye drop formulations. We conclude that mucoadhesive microparticles are promising vehicles for ophthalmic drug delivery.

Mechanical compliance of the endocardium.

Radio-frequency (RF) ablation is an accepted treatment for cardiac arrhythmias related to abnormal focal cardiac substrate. The penetration depth of the electrode into the endocardium affects lesion size, a critical determinant of success of RF ablation. We measured the relation between the mechanical compliance and the penetration depth of RF ablation catheter electrode at frequently ablated areas of the endocardium and examined the influence of time after death on mechanical properties of the tissue. We measured force versus time for eight insertion depths of the catheter electrode into full-thickness endocardial samples derived from the mitral valve annulus, the left ventricular free wall and the tricuspid valve annulus. We varied the time after death at 15, 40 min, 3, 8, and 18 h and repeated our measurements. At 15 min after death, the first 0.5mm penetration depth caused the fastest relaxation at 55 s. Force decay decreased dramatically at 15 min after death as the penetration depth increased from 0.5 to 4mm. We used the force data sampled at 60s after insertion to approximate the elasticity. We observed the relations between the force versus the insertion depth. The force increased by a factor of 5 for the mitral valve annulus and 8 for the left free wall from 15 min to 18 h. We derived coefficients of a second-order polynomial equation relating the force data to insertion depth with R(2)>0.99.