Abstract
Polylactic acid (PLA) is a biodegradable polymer commonly used as a scaffold material to repair tissue defects, and its degradation is associated with mechanical stimulus. In this study, the effect of mechanical stimulus on the degradation of 3D-printed PLA scaffolds was investigated by in vitro experiments and an author-developed numerical model. Forty-five samples with porosity 64.8% were printed to carry out the degradation experiment within 90 days. Statistical analyses of the mass, volume fraction, Young’s modulus, and number average molecular weight were made, and the in vitro experiments were further used to verify the proposed numerical model of the scaffold degradation. The results indicated that the mechanical stimulus accelerated the degradation of the PLA scaffold, and the higher mechanical stimulus led to a faster degradation of the scaffolds at the late stage of the degradation process. In addition, the Young’s modulus and the normalized number average molecular weight of the PLA scaffolds between the experiments and the numerical simulations were comparable, especially for the number average molecular weight. The present study could be helpful in the design of the biodegradable PLA scaffolds.
Highlights
Bone tissue engineering (BTE) offers a promising strategy of healing bone defects to restore their functions by utilizing the body’s natural biological response to tissue damage in conjunction with engineering principles (Amini et al, 2012)
The curled bar at the top of the dried scaffold appears at day 60, and the top of the scaffolds starts fragmenting at day 75, which attributes to the top-down loading method of in vitro experiments
The morphological change illustrates that the bar curl-up of the scaffolds is the precursor of the failure, and the high mechanical stimulus accelerates the degradation process advances the scaffold failure
Summary
Bone tissue engineering (BTE) offers a promising strategy of healing bone defects to restore their functions by utilizing the body’s natural biological response to tissue damage in conjunction with engineering principles (Amini et al, 2012). Biodegradable scaffolds are generally considered as attractive elements to provide temporary mechanical and biological supports which can facilitate regulating cell behaviors to conduct the defected bone repairment (Hutmacher, 2000). The PLA biodegradation rate is affected by many factors, including morphology, molecular weight, crystallinity, and environments (e.g., Scaffolds Degradation Under Mechanical Stimulus external mechanical stimuli, pH value, and temperature) (Reed and Gilding, 1981; Vert, 2005; Fan et al, 2008). Mechanical stimulus represents a crucial factor affecting the PLA degradation, and how the mechanical properties of PLA vary during the degradation of PLA scaffolds should be well revealed to understand the mechanically regulated bone recovery process. Many mathematical models have been proposed to describe the PLA degradation (Gopferich, 1996; Han and Pan, 2009; Chen et al, 2011; Sackett and Narasimhan, 2011; Shi et al, 2018), few studies verified the models by designing corresponding in vitro experiments and quantitively described the relationship between the mechanical stimulus and the PLA scaffold degradation
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