Theoretical investigation of erythrocytes optical trapping in ray optics approximation

The thesis presents a theoretical investigation of the optical trapping of erythrocytes in the ray optics approximation. The thesis is divided in two parts: Part I provides an introduction on the general background on erythrocytes and the physics underlaying the work presented in the thesis; Part II presents the results obtained during my studies. In the first chapter of Part II, I introduce the ray-tracing scheme useful to perform the geometrical optics calculations for a healthy red blood cell that will be used extensively in the thesis. Therefore, I present a methodology for the identification of the equilibrium configuration of a red blood cell (RBC) for the simple case of a single-beam optical tweezers. Then, I proceed to investigate the equilibrium configuration of a RBC optically trapped with a double-, triple- and four-beam optical tweezers comparing my results with experiments. In the second chapter of Part II, I introduce a numerical scheme useful to simulate the Brownian dynamics of a non-spherical particle in a force-field (i.e. an optically trapped particle). This scheme is then applied to investigate the possibility to control the position and orientation of a healthy RBC with a reconfigurable triple-beam optical tweezers. In the third chapter of Part II, I investigate the possibility of optically confine and deliberately rotate a healthy RBC with a light-sheet optical tweezers (i.e. beam focused over a line instead of a point). In the fourth chapter of Part II, I present the research carried out in collaboration with Nano-Soft Lab at CNR in Messina, Italy. Here we couple the geometrical optics calculation with machine learning to improve the accuracy and the speed of geometrical optics calculations. Lastly, in the fifth chapter of Part II, I extend the work presented in the previous chapters to a pathological RBC conformation (i.e. sickle cell)

A Multifunctional Nanocomposite Hydrogel for Endoscopic Tracking and Manipulation

Herein, the fabrication of multi‐responsive and hierarchically organized nanomaterial using core‐shell SrF2 upconverting nanoparticles, doped with Yb3+, Tm3+, Nd3+ incorporated into gelatin methacryloyl matrix, is reported. Upon 800 nm excitation, deep monitoring of 3D‐printed constructs is demonstrated. Addition of magnetic self‐assembly of iron oxide nanoparticles within the hydrogel provides anisotropic structuration from the nano‐ to the macro‐scale and magnetic responsiveness permitting remote manipulation. The present study provides a new strategy for the fabrication of a novel highly organized multi‐responsive material using additive manufacturing, which can have important implications in biomedicine

Ray Optics Model for Optical Trapping of Biconcave Red Blood Cells

Red blood cells (RBCs) or erythrocytes are essential for oxygenating the peripherical tissue in the human body. Impairment of their physical properties may lead to severe diseases. Optical tweezers have in experiments been shown to be a powerful tool for assessing the biochemical and biophysical properties of RBCs. Despite this success there has been little theoretical work investigating of the stability of erythrocytes in optical tweezers. In this paper we report a numerical study of the trapping of RBCs in the healthy, native biconcave disk conformation in optical tweezers using the ray optics approximation. We study trapping using both single- and dual-beam optical tweezers and show that the complex biconcave shape of the RBC is a significant factor in determining the optical forces and torques on the cell, and ultimately the equilibrium configuration of the RBC within the trap. We also numerically demonstrate how the addition of a third or even fourth trapping laser beam can be used to control the cell orientation in the optical trap. The present investigation sheds light on the trapping mechanism of healthy erythrocytes and can be exploited by experimentalist to envisage new experiments

Synthesis and characterization of peptide-imprinted nanogels of controllable size and affinity

Molecularly imprinted polymeric nanogels (nanoMIPs) are soft biomimetics with recognition properties similar to antibodies but robustness and integrability to devices (sensing, assays) typical of polymers. Aiming at tailor-made at-will the recognition and physical properties of these biomimetics, we investigated the process of stamping analytes of clinical relevance, i.e. an idiotipic peptide of Troponin I, on protein-compatible soft-material at the nanoscale. Highly crosslinked poly(acrylamide-co-methacrylic acid) nanoparticles were prepared by precipitation polymerization via free radical initiation. The influence of the monomer composition to the nanogel hydrodynamic size was observed by dynamic light scattering and scanning electron microscopy. The effect of the total monomers to template (TM:T) molar ratio on the formation of the binding sites was investigated thermodynamically. Results indicate rules for the manipulation of the nanogel sizes, showing the pivotal role of hydrophobic interactions in confining the polymerization to the nanoscale (∼60 nm). The efficacy of the stamping process in the chosen polymerization conditions resulted maximal for TM:T molar ratios in the range 175:1–437:1. NanoMIPs with nanomolar dissociation constants for the template and a mean number of one binding site per particle were produced. Overall the results set conditions for preparing synthetic recognition nanoparticles acting as peptide-recognition elements

A Stimuli-Responsive Nanocomposite for 3D Anisotropic Cell-Guidance and Magnetic Soft Robotics

Stimuli‐responsive materials have the potential to enable the generation of new bioinspired devices with unique physicochemical properties and cell‐instructive ability. Enhancing biocompatibility while simplifying the production methodologies, as well as enabling the creation of complex constructs, i.e., via 3D (bio)printing technologies, remains key challenge in the field. Here, a novel method is presented to biofabricate cellularized anisotropic hybrid hydrogel through a mild and biocompatible process driven by multiple external stimuli: magnetic field, temperature, and light. A low‐intensity magnetic field is used to align mosaic iron oxide nanoparticles (IOPs) into filaments with tunable size within a gelatin methacryloyl matrix. Cells seeded on top or embedded within the hydrogel align to the same axes of the IOPs filaments. Furthermore, in 3D, C2C12 skeletal myoblasts differentiate toward myotubes even in the absence of differentiation media. 3D printing of the nanocomposite hydrogel is achieved and creation of complex heterogeneous structures that respond to magnetic field is demonstrated. By combining the advanced, stimuli‐responsive hydrogel with the architectural control provided by bioprinting technologies, 3D constructs can also be created that, although inspired by nature, express functionalities beyond those of native tissue, which have important application in soft robotics, bioactuators, and bionic devices

A Multifunctional Nanocomposite Hydrogel for Endoscopic Tracking and Manipulation

Herein, the fabrication of multi‐responsive and hierarchically organized nanomaterial using core‐shell SrF2 upconverting nanoparticles, doped with Yb3+, Tm3+, Nd3+ incorporated into gelatin methacryloyl matrix, is reported. Upon 800 nm excitation, deep monitoring of 3D‐printed constructs is demonstrated. Addition of magnetic self‐assembly of iron oxide nanoparticles within the hydrogel provides anisotropic structuration from the nano‐ to the macro‐scale and magnetic responsiveness permitting remote manipulation. The present study provides a new strategy for the fabrication of a novel highly organized multi‐responsive material using additive manufacturing, which can have important implications in biomedicine

A Stimuli-Responsive Nanocomposite for 3D Anisotropic Cell-Guidance and Magnetic Soft Robotics

Stimuli‐responsive materials have the potential to enable the generation of new bioinspired devices with unique physicochemical properties and cell‐instructive ability. Enhancing biocompatibility while simplifying the production methodologies, as well as enabling the creation of complex constructs, i.e., via 3D (bio)printing technologies, remains key challenge in the field. Here, a novel method is presented to biofabricate cellularized anisotropic hybrid hydrogel through a mild and biocompatible process driven by multiple external stimuli: magnetic field, temperature, and light. A low‐intensity magnetic field is used to align mosaic iron oxide nanoparticles (IOPs) into filaments with tunable size within a gelatin methacryloyl matrix. Cells seeded on top or embedded within the hydrogel align to the same axes of the IOPs filaments. Furthermore, in 3D, C2C12 skeletal myoblasts differentiate toward myotubes even in the absence of differentiation media. 3D printing of the nanocomposite hydrogel is achieved and creation of complex heterogeneous structures that respond to magnetic field is demonstrated. By combining the advanced, stimuli‐responsive hydrogel with the architectural control provided by bioprinting technologies, 3D constructs can also be created that, although inspired by nature, express functionalities beyond those of native tissue, which have important application in soft robotics, bioactuators, and bionic devices