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Pizzi M, De Gaetano F, Ferroni M, Boschetti F, Annoni M. A Deep-Hole Microdrilling Study of Pure Magnesium for Biomedical Applications. MICROMACHINES 2023; 14:132. [PMID: 36677193 PMCID: PMC9863778 DOI: 10.3390/mi14010132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 12/21/2022] [Accepted: 12/28/2022] [Indexed: 06/17/2023]
Abstract
The mechanisms of deep-hole microdrilling of pure Mg material were experimentally studied in order to find a suitable setup for a novel intraocular drug delivery device prototyping. Microdrilling tests were performed with 0.20 mm and 0.35 mm microdrills, using a full factorial design in which cutting speed vc and feed fz were varied over two levels. In a preliminary phase, the chip shape was evaluated for low feeds per tooth down to 1 μm, to verify that the chosen parameters were appropriate for machining. Subsequently, microdrilling experiments were carried out, in which diameter, burr height and surface roughness of the drilled holes were examined. The results showed that the burr height is not uniform along the circumference of the holes. In particular, the maximum burr height increases with higher cutting speed, due to the thermal effect that plasticizes Mg. Hole entrance diameters are larger than the nominal tool diameters due to tool runout, and their values are higher for high vc and fz. In addition, the roughness of the inner surface of the holes increases as fz increases.
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Affiliation(s)
- Margherita Pizzi
- Department of Mechanical Engineering, Politecnico di Milano, 20156 Milan, Italy
| | - Francesco De Gaetano
- Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, 20133 Milan, Italy
- MgShell S.r.l., 20133 Milan, Italy
| | - Marco Ferroni
- Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, 20133 Milan, Italy
- MgShell S.r.l., 20133 Milan, Italy
| | - Federica Boschetti
- Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, 20133 Milan, Italy
| | - Massimiliano Annoni
- Department of Mechanical Engineering, Politecnico di Milano, 20156 Milan, Italy
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Velentza-Almpani A, Ibeanu N, Liu T, Redhead C, Tee Khaw P, Brocchini S, Awwad S, Bouremel Y. Effects of Flow Hydrodynamics and Eye Movements on Intraocular Drug Clearance. Pharmaceutics 2022; 14:pharmaceutics14061267. [PMID: 35745839 PMCID: PMC9229170 DOI: 10.3390/pharmaceutics14061267] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 06/09/2022] [Accepted: 06/12/2022] [Indexed: 02/06/2023] Open
Abstract
New in vitro prototypes (PK-Eye™) were tested with and without eye movement to understand diffusion and convection effects on intraocular clearance. Port placement in front ((i) ciliary inflow model) and behind the model lens ((ii) posterior inflow model) was used to study bevacizumab (1.25 mg/50 µL) and dexamethasone (0.1 mg/100 µL) in phosphate-buffered saline (PBS, pH 7.4) and simulated vitreal fluid (SVF). Dexamethasone was studied in a (iii) retinal-choroid-sclera (RCS) outflow model (with ciliary inflow and two outflow pathways). Ciliary vs. posterior inflow placement did not affect the half-life for dexamethasone at 2.0 µL/min using PBS (4.7 days vs. 4.8 days) and SVF (4.9 days with ciliary inflow), but it did decrease the half-life for bevacizumab in PBS (20.4 days vs. 2.4 days) and SVF (19.2 days vs. 10.8 days). Eye movement only affected the half-life of dexamethasone in both media. Dexamethasone in the RCS model showed approximately 20% and 75% clearance from the RCS and anterior outflows, respectively. The half-life of the protein was comparable to human data in the posterior inflow model. Shorter half-life values for a protein in a ciliary inflow model can be achieved with other eye movements. The RCS flow model with eye movement was comparable to human half-life data for dexamethasone.
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Affiliation(s)
- Angeliki Velentza-Almpani
- Optceutics Ltd., 28a Menelik Road, London NW2 3RP, UK; (A.V.-A.); (N.I.); (T.L.); (C.R.); (P.T.K.); (S.B.)
- Department of Pharmaceutics, UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Nkiruka Ibeanu
- Optceutics Ltd., 28a Menelik Road, London NW2 3RP, UK; (A.V.-A.); (N.I.); (T.L.); (C.R.); (P.T.K.); (S.B.)
- Department of Pharmaceutics, UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
- National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London EC1V 9EL, UK
| | - Tianyang Liu
- Optceutics Ltd., 28a Menelik Road, London NW2 3RP, UK; (A.V.-A.); (N.I.); (T.L.); (C.R.); (P.T.K.); (S.B.)
- Department of Pharmaceutics, UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Christopher Redhead
- Optceutics Ltd., 28a Menelik Road, London NW2 3RP, UK; (A.V.-A.); (N.I.); (T.L.); (C.R.); (P.T.K.); (S.B.)
| | - Peng Tee Khaw
- Optceutics Ltd., 28a Menelik Road, London NW2 3RP, UK; (A.V.-A.); (N.I.); (T.L.); (C.R.); (P.T.K.); (S.B.)
- National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London EC1V 9EL, UK
| | - Steve Brocchini
- Optceutics Ltd., 28a Menelik Road, London NW2 3RP, UK; (A.V.-A.); (N.I.); (T.L.); (C.R.); (P.T.K.); (S.B.)
- Department of Pharmaceutics, UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
- National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London EC1V 9EL, UK
| | - Sahar Awwad
- Optceutics Ltd., 28a Menelik Road, London NW2 3RP, UK; (A.V.-A.); (N.I.); (T.L.); (C.R.); (P.T.K.); (S.B.)
- Department of Pharmaceutics, UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
- National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London EC1V 9EL, UK
- Correspondence: (S.A.); (Y.B.); Tel.: +44-207-753-5802 (S.A.)
| | - Yann Bouremel
- Optceutics Ltd., 28a Menelik Road, London NW2 3RP, UK; (A.V.-A.); (N.I.); (T.L.); (C.R.); (P.T.K.); (S.B.)
- Department of Pharmaceutics, UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
- National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London EC1V 9EL, UK
- Correspondence: (S.A.); (Y.B.); Tel.: +44-207-753-5802 (S.A.)
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Li H, Zhu X, Wang M, Zhao D, Li H, Yan J. Drug sustained release from degradable drug-loaded in-situ hydrogels in the posterior eye: a mechanistic model and analytical method. J Biomech 2022; 136:111052. [DOI: 10.1016/j.jbiomech.2022.111052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 02/10/2022] [Accepted: 02/28/2022] [Indexed: 11/28/2022]
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Ocular Fluid Mechanics and Drug Delivery: A Review of Mathematical and Computational Models. Pharm Res 2021; 38:2003-2033. [PMID: 34936067 DOI: 10.1007/s11095-021-03141-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 11/10/2021] [Indexed: 10/19/2022]
Abstract
The human eye is a complex biomechanical structure with a range of biomechanical processes involved in various physiological as well as pathological conditions. Fluid flow inside different domains of the eye is one of the most significant biomechanical processes that tend to perform a wide variety of functions and when combined with other biophysical processes play a crucial role in ocular drug delivery. However, it is quite difficult to comprehend the effect of these processes on drug transport and associated treatment experimentally because of ethical constraints and economic feasibility. Computational modeling on the other hand is an excellent means to understand the associated complexity between these aforementioned processes and drug delivery. A wide range of computational models specific to different types of fluids present in different domains of the eye as well as varying drug delivery modes has been established to understand the fluid flow behavior and drug transport phenomenon in an insilico manner. These computational models have been used as a non-invasive tool to aid ophthalmologists in identifying the challenges associated with a particular drug delivery mode while treating particular eye diseases and to advance the understanding of the biomechanical behavior of the eye. In this regard, the author attempts to summarize the existing computational and mathematical approaches proposed in the last two decades for understanding the fluid mechanics and drug transport associated with different domains of the eye, together with their application to modify the existing treatment processes.
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Ferroni M, De Gaetano F, Cereda MG, Boschetti F. Evaluation of the ocular fluid dynamic effects on intraocular magnesium-based device: A comparison between CFD and FSI approaches. Med Eng Phys 2020; 86:20-28. [PMID: 33261729 DOI: 10.1016/j.medengphy.2020.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 09/04/2020] [Accepted: 10/05/2020] [Indexed: 11/28/2022]
Abstract
Magnesium is an essential element for the ocular functions and used for the realization of medical devices due to its low corrosion resistance, bioresorbable nature and biocompatibility. Wet age-related macular degeneration is one of the main causes of blindness with patients treated by intravitreal injections of inhibitor drugs. According to the need to reduce the number of injections, the development of new drug delivery devices able to extend the therapeutical outcomes is mandatory and magnesium can be considered as a promising candidate. The aim of the work concerns the evaluation of the ocular fluid dynamic role on a magnesium-based device placed in the vitreous chamber. Particularly, the fluid-induced shear stress field on the surfaces in contact with the liquefied vitreous was studied. Both computational fluid dynamic and fluid-structure interaction approaches were proposed and then compared. Saccadic motion was implemented to recreate the vitreous fluid dynamics. High changes in terms of fluid-induced shear stress field varying the CFD and FSI numerical approaches and kinematic parameters of the saccadic function can be noticed. The comparison between CFD and FSI approaches showed minor significant differences and both implementations suggested the possibility to obtain a uniform and controlled corrosion of the device.
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Affiliation(s)
- Marco Ferroni
- LaBS, Chemistry Materials and Chemical Engineering Department "Giulio Natta", Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milan, Italy; MgShell S.r.l., Milan, Italy.
| | - Francesco De Gaetano
- LaBS, Chemistry Materials and Chemical Engineering Department "Giulio Natta", Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milan, Italy; MgShell S.r.l., Milan, Italy
| | - Matteo Giuseppe Cereda
- Eye Clinic, Department of Biomedical and clinical science "Luigi Sacco", Sacco Hospital, University of Milan, Via G.B. Grassi 74, 20157 Milan, Italy
| | - Federica Boschetti
- LaBS, Chemistry Materials and Chemical Engineering Department "Giulio Natta", Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milan, Italy
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Tram NK, Maxwell CJ, Swindle-Reilly KE. Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport. Curr Eye Res 2020; 46:429-444. [PMID: 33040616 DOI: 10.1080/02713683.2020.1826977] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Research on the vitreous humor and development of hydrogel vitreous substitutes have gained a rapid increase in interest within the past two decades. However, the properties of the vitreous humor and vitreous substitutes have yet to be consolidated. In this paper, the mechanical properties of the vitreous humor and hydrogel vitreous substitutes were systematically reviewed. The number of publications on the vitreous humor and vitreous substitutes over the years, as well as their respective testing conditions and testing techniques were analyzed. The mechanical properties of the human vitreous were found to be most similar to the vitreous of pigs and rabbits. The storage and loss moduli of the hydrogel vitreous substitutes developed were found to be orders of magnitude higher in comparison to the native human vitreous. However, the reported modulus for human vitreous, which was most commonly tested in vitro, has been hypothesized to be different in vivo. Future studies should focus on testing the mechanical properties of the vitreous in situ or in vivo. In addition to its mechanical properties, the vitreous humor has other biotransport mechanisms and biochemical functions that establish a redox balance and maintain an oxygen gradient inside the vitreous chamber to protect intraocular tissues from oxidative damage. Biomimetic hydrogel vitreous substitutes have the potential to provide ophthalmologists with additional avenues for treating and controlling vitreoretinal diseases while preventing complications after vitrectomy. Due to the proximity and interconnectedness of the vitreous humor to other ocular tissues, particularly the lens and the retina, more interest has been placed on understanding the properties of the vitreous humor in recent years. A better understanding of the properties of the vitreous humor will aid in improving the design of biomimetic vitreous substitutes and enhancing intravitreal biotransport.
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Affiliation(s)
- Nguyen K Tram
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Courtney J Maxwell
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Katelyn E Swindle-Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA.,William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, USA.,Department of Ophthalmology & Visual Science, The Ohio State University, Columbus, OH, USA
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A drug delivery analysis of large molecules in ocular vitreous chamber: Dependency on saccadic movements after intravitreal injection. Med Eng Phys 2020; 82:49-57. [PMID: 32709265 DOI: 10.1016/j.medengphy.2020.06.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 05/14/2020] [Accepted: 06/15/2020] [Indexed: 02/06/2023]
Abstract
The purpose of this study is to investigate the effect of vitreous sloshing induced by saccades on the intravitreal delivery of large molecule drugs. The vitreous body was considered in its age-related liquefaction condition. Fluid dynamics and large molecule distribution were described by the coupling of mass conservation's and Fick's laws with continuity and momentum equations for a Newtonian incompressible fluid in a 3D unsteady analysis. Two injection sites were analyzed, in both the mixing effect of a 50° periodic saccade leads to uniform drug distribution in 30 s of simulation, the initial bolus site being left after 3 s of simulation. In absence of saccadic movements, the dominant transport contribution is the diffusive one and large molecules hardly reach their uniform distribution inside the vitreous cavity. A model describing the intravitreal distribution of large molecules in presence of saccades was developed, improving the understanding of drug transport mechanism after an intravitreal injection and highlighting how advection contribution enhances its distribution in the vitreous chamber.
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