Functionalised biomimetic hydroxyapatite NPs as potential agent against pathogenic multidrug-resistant bacteria

Abstract

The persistent dissemination of resistant bacterial strains is a grave contemporary global impediment in hospital-acquired infections which needs to be mitigated with immediate effect. In particular, infections from pathogenic multidrug-resistant (MDR) Gram-positive bacteria (like Enterococcus faecalis) which are resistant to conventional antibiotic therapy are attracting immediate global attention. Here we report the synthesis of nanoscale hydroxyapatites (HAPs), which are the well known biomimetic ceramic material having needle shaped morphologies. We have encapsulated vancomycin (VAN) within these nanoparticles and have conjugated the targeting ligand (folic acid) by a facile synthesis process in order to enhance the therapeutic efficacy against MDR E. faecalis. These functionalised HAPs are thoroughly characterised by employing field emission scanning electron microscopy (FESEM), powder x-ray diffraction (PXRD), ultraviolet–visible spectroscopy (UV-Vis) and dynamic light-scattering (DLS) techniques. Our results suggest that these functionalised HAPs could successfully transport vancomycin across the cell wall of MDR E. faecalis through endocytosis. The determination of selective antibacterial activity has been envisaged with the help of extensive in-vitro assays like the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and the generation of reactive oxygen species (ROS). This study vividly establishes that this folic acid conjugated HAPs are promising antibacterial agents against MDR E. faecalis and related pathogenic resistant bacterial strains.

Phytofabrication of silver nano particles using <em>Ocimum sanctum </em>leaf extract and their antibacterial and anticancer activity through oxidative damage

“…We have also studied the mechanism behind the bacterial growth inhibition. Our present experiments with biogenic AgNP, destruction of bacterial cell wall might have caused due to one or multiple steps of signaling cascades resulting in defective cell wall synthesis or impaired cross-linking of polymer units, which have occurred due to the ROS generation in both Gram-positive and Gram-negative bacterial strains [28,29]. Silver ions have a great impact on altered cellular metabolism inhibiting proliferation and metastasis of cancer cells.…”

“…According to our previously reported protocol [28,29], MIC and MBC were evaluated by microdilution method in Luria broth. Different concentrations of AgNPs were added to the bacterial media containing the inoculums and incubated for 24 hrs.…”

“…The tolerance levels of each bacterial strain against AgNP were determined by using the following formula [28,30].…”

“…Wells (diameter 2 = 0.563cm 2 ) were punched in the agar plates and treated with AgNPs at their MBC concentrations. The zone of inhibition diameter in the bacterial growth surrounding the disc (including the disc) was measured [28,30].…”

“…The viability of bacterial cells was analysed with help of 3-(4, 5-dimethylthiazol-2-yl) -2, 5diphenyltetrazolium bromide (MTT) following a standard protocol [28]. Cell viability was determined after exposure to different concentrations of AgNPs for 24 hrs at 37° C. After incubation, the bacterial cells were collected and centrifuged at 1400 rpm for 10 mins at 4° C then washed three times with sterile phosphate buffered saline (PBS, pH 7.4).…”