An Implanted Magnetic Microfluidic Pump for In Vivo Bone Remodeling Applications.

Ziyu Chen,Rhonda D Prisby,Sunggi Noh,Jeong-Bong Lee

doi:10.3390/mi11030300

Ziyu Chen, Rhonda D Prisby + Show 2 more

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https://doi.org/10.3390/mi11030300

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Abstract

Modulations of fluid flow inside the bone intramedullary cavity has been found to stimulate bone cellular activities and augment bone growth. However, study on the efficacy of the fluid modulation has been limited to external syringe pumps connected to the bone intramedullary cavity through the skin tubing. We report an implantable magnetic microfluidic pump which is suitable for in vivo studies in rodents. A compact microfluidic pump (22 mm diameter, 5 mm in thickness) with NdFeB magnets was fabricated in polydimethylsiloxane (PDMS) using a set of stainless-steel molds. An external actuator with a larger magnet was used to wirelessly actuate the magnetic microfluidic pump. The characterization of the static pressure of the microfluidic pump as a function of size of magnets was assessed. The dynamic pressure of the pump was also characterized to estimate the output of the pump. The magnetic microfluidic pump was implanted into the back of a Fischer-344 rat and connected to the intramedullary cavity of the femur using a tube. On-demand wireless magnetic operation using an actuator outside of the body was found to induce pressure modulation of up to 38 mmHg inside the femoral intramedullary cavity of the rat.

Highlights

Osteoporosis is a bone disorder that increases a person’s risk of fracture due to low bone mineral density, impaired bone microarchitecture/mineralization, and/or decreased bone strength [1]
Evidence accumulated over the years has suggested that one of the primary causes of bone remodeling is due to intramedullary fluid flow fluctuation under mechanical loading [7,8]
It is suggested that shear stress induced by augmented fluid flow and pressure in the cavity elicits the release of bone stimulating factors [11], such as nitric oxide (NO) and prostaglandins (e.g., PGE2) [12,13]

Summary

Introduction

Osteoporosis is a bone disorder that increases a person’s risk of fracture due to low bone mineral density, impaired bone microarchitecture/mineralization, and/or decreased bone strength [1]. In contrast to the amount of studies performed in vitro, in vivo studies that demonstrate modulated intramedullary fluid pressure and/or flow mediate bone remodeling in response to mechanical loading are scarce. A few studies have demonstrated that oscillatory intramedullary fluid flow loading alone in the absence of bone mechanical loading can result in the desired augmentation of bone formation in turkey ulnae [23] and hindlimb suspended mice [24]. These observations suggest that intramedullary fluid flow and pressure modulation without mechanical loading could be a non-pharmaceutical alternative to treat osteoporosis and facilitate bone fracture healing

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