Reagent grade salts

Two methods for HAp coating of porous Ti matrix were employed: biomimetic coating process and electrochemical deposition. In the biomimetic coating procedure, saturated simulated body fluid (5x SBF) was used according to a previously published method [30 (link)]. Briefly, coating solutions A and B were prepared (Table 1) by dissolving reagent grade salts (Sigma-Aldrich, UK) at 37°C with a constant 5% CO₂ supply and stirring in distilled water. Samples were firstly soaked in solution A, for 24 or 48 hrs at 37°C and then in solution B for 48 hrs at 40°C with constant stirring.
In the electrochemical method, titanium lattices were immersed in the CaP solution (0.13 M, Ca(H₂PO₄)₂, Sigma-Aldrich, UK) and attached to the negative terminal of a DC Dual Power Supply pack (Peak Tech, Telonic Instruments Ltd, UK). Two different electrical current densities of 10 and 6 mA/cm² were applied between the two electrodes for 10 mins. The samples were then soaked in 0.1 M NaOH solution for 72 h, cleaned in distilled water, and air-dried. Scaffold formulations are summarized in Table 2.
Morphology of deposited HAp was observed by scanning electron microscopy (SEM, JEOL JSM 5500 LV, at 10 kV) and elemental analysis was performed by energy dispersive X-ray spectroscopy (EDAX, EDAX Inc., USA).

Spectrum™ Labs Regenerated Cellulose (RC) dialysis membranes with molecular weight cutoffs (MWCO)s of 50 kDa (08-700-128), 100 kDa (08-700-132) and 1000 kDa (08-801-255) were purchased from Fisher Scientific (Waltham, MA, USA). The tri-angular Pyrex-Nitride AFM probes (PNP-TR-20) were purchased from NanoWorld (Neuchâtel, Switzerland). The AFM Calibration block (TGZ1) characterized by a step height of 20 ± 1.5 nm was purchased from Ted Pella Inc. (Redding, CA, USA). Fluorescein isothiocyanate dextran MW markers, 4 kDa (FD), as well reagent grade salts were purchased from Sigma Aldrich (Saint Louis, MO, USA).

Nutrient solutions were mixed using deionized water and reagent grade salts (Sigma Aldrich). Table 1 shows the composition of the nutrient solution. The concentration of elements followed mass balance principles as described by Bugbee (2004) (link) and Langenfeld et al. (2022) (link).