Gentamicin release from two‐solution and powder–liquid poly(methyl methacrylate)‐based bone cements by using novel pH method

Abstract

The release of gentamicin as a function of time was measured for Palacos and two-solution bone cements by using a novel pH technique. The pH of an aqueous solution of gentamicin is a function of the gentamicin concentration and it decreases linearly over concentrations of 0.0-0.1 wt %. Therefore, a new, direct, and inexpensive in vitro technique was developed based on continuous readings of the pH in phosphate-buffered saline (PBS) at 37 degrees C to determine the release kinetics of gentamicin from poly(methyl methacrylate) (PMMA)-based bone cement. In addition, this method was used to compare the release profiles of Palacos R-40 bone cement with a two-solution bone cement developed in our laboratory and loaded with two different concentrations of gentamicin sulfate. Finally, the pH-based method was used to track the elution of gentamicin in both mixed and static conditions to determine the effect of mixing on the diffusion of gentamicin out of the cement. It was found that Palacos R-40 released 4.95 +/- 0.22 wt % of its gentamicin after 24 h in PBS solution. This data compares favorably with previously reported values of gentamicin elution from Palacos R-40, which ranged from 3 to 8 wt % of the total amount of incorporated gentamicin, depending on the size and the surface area of the samples. The results show that Palacos samples released 4.84 +/- 0.27 mg after 24 h, a two-solution cement loaded with an equivalent concentration of gentamicin sulfate released 3.81 +/- 0.52 mg, and two-solution cement loaded with twice the concentration of Palacos released 5.53 +/- 0.26 mg of gentamicin. A higher percentage of release was recorded from Palacos than from the two-solution bone cement, and the effect of PBS mixing conditions on the release kinetics was only significant in the early stages of release and not at 24 h. It was concluded that monitoring the pH is an effective technique to measure gentamicin release from PMMA-based bone cements in PBS solution.

Properties of antibiotic‐loaded acrylic bone cements for use in cemented arthroplasties: A state‐of‐the‐art review

“…At early time points (<∼3 h), the amount of gentamicin eluted (cumulative and mass percentage) from Palacos R+G specimens immersed in PBS at 37°C was significantly higher when the test solution was magnetically stirred than when it was static but there was no significant difference between the two conditions in the total amount eluted after 24 h 66. This trend suggests that a higher rate of release of the antibiotic from the specimen surface is stimulated by making a homogeneous concentration of the gentamicin in the case of the stirred solution.…”

“…When mixed, the two solutions polymerize via a free radical reaction. Relative to Palacos R‐40 loaded with 0.5 g of gentamicin, a lower percentage of gentamicin eluted from specimens of a two‐solution cement loaded with the gentamicin (in amounts either equivalent to the concentration in Palacos R‐G or twice that concentration) when immersed in PBS at 37°C, over a period of 24 h. This trend is a consequence of the fact that, compared to the gentamicin‐loaded Palacos R‐40 specimens, the two‐solution cement specimens had lower bulk porosity, a higher molecular weight of the polymerized matrix, lower concentration of the radiopacifier in the cement matrix, and lower absorption of water 66…”

An Approach for Determining Antibiotic Loading for a Physician-directed Antibiotic-loaded PMMA Bone Cement Formulation

“…5). This pattern of elution is typical for ''low-dose'' and ''medium-dose'' (antibiotic loading between 5 wt/wt% and 10 wt/wt%) ALBC formulations [7,10,24]. The best-fit relationships between the concentration of the eluted daptomycin (CON) and t (over the time range 1 day B t B 7 days) (Fig.…”

Foot and Ankle Reconstruction After Blast Injuries

“…Based on the results of initial cultures, vancomycin, 1 g, tobramycin, 2.4 g, or iminipenem alone or in combination are used per packet of Palacos R (Zimmer, Warsaw, Indiana) polymer to form the beads or spacers. In several studies, Palacos R demonstrated an increased elution of antibiotics when compared with other formulations of PMMA [54][55][56][57]. In the foot and ankle, antibiotic-impregnated PMMA spacer blocks are preferable to beads to fill the osseous void created by the projectile and to hold the soft tissues at normal tension.…”