Decellularized Spinach Biomaterials Support Physiologically Relevant Mechanical Cyclic Strain and Prompt a Stretch-Induced Cellular Response

Recently, decellularized plant biomaterials have been explored for their use as tissue engineered substitutes. Herein, we expanded upon the investigation of the mechanical properties of these materials to explore their elasticity as many anatomical areas of the body require biomechanical dynamism. We first constructed a device to secure the scaffold and induce a strain within the physiological range of the normal human adult lung during breathing (12-20 movements/min; 10-20% elongation). Results showed that decellularized spinach leaves can support cyclic strain for 24 h and displayed heterogeneous local strain values (7.76-15.88%) as well as a Poisson's ratio (0.12) similar to that of mammalian lungs (10.67-19.67%; 0.01), as opposed to an incompressible homogeneous standard polymer (such as PDMS (10.85-12.71%; 0.4)). Imaging and mechanical testing showed that the vegetal scaffold exhibited strain hardening but maintained its structural architecture and water retention capacity, suggesting an unaltered porosity. Interestingly, we also showed that cells seeded on the scaffold can also sense the mechanical strain as demonstrated by a nuclear reorientation perpendicular to strain direction (63.3° compared to 41.2° for nonstretched cells), a nuclear location of YAP and increased expression of YAP target genes, a high cytoplasmic calcium level, and an elevated expression level of collagen genes (COL1A1, COL3A1, COL4A1, and COL6A) with an increased collagen secretion at the protein level. Taken together, these data demonstrated that decellularized plant leaf tissues have an inherent elastic property similar to that found in the mammalian system to which cells can sense and respond.

The Emerging Role of Decellularized Plant-Based Scaffolds as a New Biomaterial

The decellularization of plant-based biomaterials to generate tissue-engineered substitutes or in vitro cellular models has significantly increased in recent years. These vegetal tissues can be sourced from plant leaves and stems or fruits and vegetables, making them a low-cost, accessible, and sustainable resource from which to generate three-dimensional scaffolds. Each construct is distinct, representing a wide range of architectural and mechanical properties as well as innate vasculature networks. Based on the rapid rise in interest, this review aims to detail the current state of the art and presents the future challenges and perspectives of these unique biomaterials. First, we consider the different existing decellularization techniques, including chemical, detergent-free, enzymatic, and supercritical fluid approaches that are used to generate such scaffolds and examine how these protocols can be selected based on plant cellularity. We next examine strategies for cell seeding onto the plant-derived constructs and the importance of the different functionalization methods used to assist in cell adhesion and promote cell viability. Finally, we discuss how their structural features, such as inherent vasculature, porosity, morphology, and mechanical properties (i.e., stiffness, elasticity, etc.) position plant-based scaffolds as a unique biomaterial and drive their use for specific downstream applications. The main challenges in the field are presented throughout the discussion, and future directions are proposed to help improve the development and use of vegetal constructs in biomedical research.

Evaluation of supercritical CO2 sterilization efficacy for sanitizing personal protective equipment from the coronavirus SARS-CoV-2

The purpose of this research is to evaluate the supercritical carbon dioxide (scCO₂) sterilization-based NovaClean process for decontamination and reprocessing of personal protective equipment (PPE) such as surgical masks, cloth masks, and N95 respirators. Preliminarily, Bacillus atrophaeus were inoculated into different environments (dry, hydrated, and saliva) to imitate coughing and sneezing and serve as a "worst-case" regarding challenged PPE. The inactivation of the microbes by scCO₂ sterilization with NovaKill or H₂O₂ sterilant was investigated as a function of exposure times ranging from 5 to 90 min with a goal of elucidating possible mechanisms. Also, human coronavirus SARS-CoV-2 and HCoV-NL63 were inoculated on the respirator material, and viral activity was determined post-treatment. Moreover, we investigated the reprocessing ability of scCO₂-based decontamination using wettability testing and surface mapping. Different inactivation mechanisms have been identified in scCO₂ sanitization, such as membrane damage, germination defect, and dipicolinic acid leaks. Moreover, the viral sanitization results showed a complete inactivation of both coronavirus HCoV-NL63 and SARS-CoV-2. We did not observe changes in PPE morphology, topographical structure, or material integrity, and in accordance with the WHO recommendation, maintained wettability post-processing. These experiments establish a foundational understanding of critical elements for the decontamination and reuse of PPE in any setting and provide a direction for future research in the field.

Supercritical carbon dioxide decellularization of plant material to generate 3D biocompatible scaffolds

The use of plant-based biomaterials for tissue engineering has recently generated interest as plant decellularization produces biocompatible scaffolds which can be repopulated with human cells. The predominant approach for vegetal decellularization remains serial chemical processing. However, this technique is time-consuming and requires harsh compounds which damage the resulting scaffolds. The current study presents an alternative solution using supercritical carbon dioxide (scCO2). Protocols testing various solvents were assessed and results found that scCO2 in combination with 2% peracetic acid decellularized plant material in less than 4 h, while preserving plant microarchitecture and branching vascular network. The biophysical and biochemical cues of the scCO2 decellularized spinach leaf scaffolds were then compared to chemically generated scaffolds. Data showed that the scaffolds had a similar Young's modulus, suggesting identical stiffness, and revealed that they contained the same elements, yet displayed disparate biochemical signatures as assessed by Fourier-transform infrared spectroscopy (FTIR). Finally, human fibroblast cells seeded on the spinach leaf surface were attached and alive after 14 days, demonstrating the biocompatibility of the scCO2 decellularized scaffolds. Thus, scCO2 was found to be an efficient method for plant material decellularization, scaffold structure preservation and recellularization with human cells, while performed in less time (36 h) than the standard chemical approach (170 h).

Plant-Based Scaffolds Modify Cellular Response to Drug and Radiation Exposure Compared to Standard Cell Culture Models

Plant-based scaffolds present many advantages over a variety of biomaterials. Recent studies explored their potential to be repopulated with human cells and thus highlight a growing interest for their use in tissue engineering or for biomedical applications. However, it is still unclear if these in vitro plant-based scaffolds can modify cell phenotype or affect cellular response to external stimuli. Here, we report the characterization of the mechano-regulation of melanoma SK-MEL-28 and prostate PC3 cells seeded on decellularized spinach leaves scaffolds, compared to cells deposited on standard rigid cell culture substrate, as well as their response to drug and radiation treatment. The results showed that YAP/TAZ signaling was downregulated, cellular morphology altered and proliferation rate decreased when cells were cultured on leaf scaffold. Interestingly, cell culture on vegetal scaffold also affected cellular response to external stress. Thus, SK-MEL-28 cells phenotype is modified leading to a decrease in MITF activity and drug resistance, while PC3 cells showed altered gene expression and radiation response. These findings shed lights on the decellularization of vegetal materials to provide substrates that can be repopulated with human cells to better reproduce a soft tissue microenvironment. However, these complex scaffolds mediate changes in cell behavior and in order to exploit the capability of matching physical properties of the various plant scaffolds to diverse physiological functionalities of cells and human tissue constructs, additional studies are required to better characterize physical and biochemical cell-substrate interactions.

Fatal pulmonary embolism: a study of genetic and acquired factors

BACKGROUND

Investigators speculate that hereditary thrombotic disease coupled with acquired factors account for a large number of pulmonary thromboemboli. Clinical correlation between genetic and acquired factors with fatal pulmonary thromboemboli has not been extensively studied.

METHODS

Archival autopsy material was obtained from patients who died of or with pulmonary emboli for whom confirmed autopsy results were available. Polymerase chain reaction-restriction fragment length polymorphism analysis was performed for factor V Leiden and factor II/20210A allele. Retrospective chart review was performed to determine the presence or absence of acquired factors that can predispose to pulmonary thromboemboli.

RESULTS

Two of 36 patients (5.5%) were heterozygous for factor V Leiden. No patients had detected abnormalities for factor II/20210A allele. Eight patients (22.2%) had a malignancy present, one of whom was heterozygous for factor V Leiden. Fourteen patients (38.8%) had recent major surgery or were immobilized.

CONCLUSIONS

The incidence of factor V Leiden and factor II/20210A allele in patients with fatal pulmonary thromboemboli is not greater than published results of the incidence of these factors in the general population. Recognized acquired factors such as malignancy, recent surgery, and immobilization are frequently present in these patients. Our results suggest that genetic profiling of thrombotic disease will not replace clinical vigilance in reducing the risk for death from pulmonary thromboemboli.