Supercritical CO₂ deposition and foaming process for fabrication of biopolyester–ZnO bone scaffolds

Abstract

Subsequent supercritical CO2‐assisted deposition and foaming process followed by in situ synthesis was used to fabricate functional polylactide (PLA) and polylactide–poly(ɛ‐caprolactone) (PLA–PCL) bone scaffolds. Deposition of zinc bis(2‐thenoyltrifluoroacetonate) as a ZnO precursor onto biopolyester substrates (30 MPa; 110 °C) was followed by fast depressurization to create cellular structure. Contact time was optimized regarding the deposition yield (2 h), while PCL content in PLA was varied (1–10 wt %). Scaffolds impregnated with the precursor were treated with hydrazine alcoholic solution to obtain biopolyester–ZnO composites. Precursor synthesis and deposition onto the scaffolds was confirmed by Fourier‐transform infrared. Processed scaffolds had micron‐sized pores (d50 ∼ 20 μm). High open porosity (69–77%) and compressive strength values (2.8–8.3 MPa) corresponded to those reported for trabecular bone. PLA blending with PCL positively affected precursor deposition, crystallization rate, and compressive strength of the scaffolds. It also improved PLA surface roughness and wettability which are relevant for cell adhesion. ZnO improved compressive strength of the PLA scaffolds without significant effect on thermal stability. Analysis of structural, thermal, and mechanical properties of biopolyester–ZnO scaffolds testified a great potential of the obtained platforms as bone scaffolds. Proposed processing route is straightforward and ecofriendly, fast, easy to control, and suitable for processing of thermosensitive polymers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45824.

Green Processing of Neat Poly(lactic acid) Using Carbon Dioxide under Elevated Pressure for Preparation of Advanced Materials: A Review (2012–2022)

“…Supercritical fluid deposition (SCFD) using sc-CO 2 is an attractive alternative process for the controlled dispersion of metallic species onto or within the surface of porous solid polymers [ 144 ]. This technique consists of three steps ( Figure 8 ): (1) the dissolution of a metal complex (precursor) in a supercritical fluid, (2) its adsorption onto a polymer matrix, and (3) the conversion of the adsorbed complex to the target metal species [ 144 , 145 , 146 ]. Precursors usually used in SCFD are metal chelates, fluorinated metal chelates, and organometallic complexes soluble in sc-CO 2 [ 145 ].…”

Tailoring of advanced poly(lactic acid)‐based materials: A review

“…Process of PLA impregnation is strongly influenced by the ratio of PLA/carrier fluid/active substance, pressure, temperature, and contact time. Usually, CO 2 was used as a carrier fluid for PLA impregnation, 114,116–119 but recently use of air and N 2 was also reported 57 …”

“…The first step in gel preparation is the selection of an appropriate solvent. Different organic solvents have been reported for preparation of PLA solutions such as chloroform (CHL), 10,59,118,119,147,148,169 tetrahydrofuran (THF), 3,121,147 dichloromethane (DCM), 11,123,127,133,147 ethyl lactate (EL), 130,131 dimethylformamide (DMF), 147,175 dimethylacetamide (DMA), 147 N ‐methyl pyrrolidone, 154 and 1,4‐dioxane (DX) 2,34,129,147 . Beside dissolution in a single solvent, PLA was also dissolved in binary 4,25,147,150,174 and triple solvent systems 149 .…”

Applications and Challenges of Supercritical Foaming Technology

“…(e) Using supercritical foaming technology can encapsulate the active ingredient in a drug, such as a microporous PLGA scaffold [ 23 ]. Current research on supercritical fluid foaming and drug preparation is focused on obtaining polymer foams with higher expansion rates, such as PLA foams by supercritical fluid foaming in combination with other techniques [ 24 ], as well as improving mechanical properties, such as the compressive strength of scaffolds, by this technology [ 25 ]. The application of supercritical foaming technology in the medical field is made possible by the use of non-toxic and non-hazardous foaming agents.…”