Mechanical characterization of a fiberoptic microneedle device for controlled delivery of fluids and photothermal excitation

Microneedle system for tissue engineering and regenerative medicines: a smart and efficient therapeutic approach

The global demand for an enhanced quality of life and extended lifespan has driven significant advancements in tissue engineering and regenerative medicine. These fields utilize a range of interdisciplinary theories and techniques to repair structurally impaired or damaged tissues and organs, as well as restore their normal functions. Nevertheless, the clinical efficacy of medications, materials, and potent cells used at the laboratory level is always constrained by technological limitations. A novel platform known as adaptable microneedles has been developed to address the abovementioned issues. These microneedles offer a solution for the localized distribution of various cargos while minimizing invasiveness. Microneedles provide favorable patient compliance in clinical settings due to their effective administration and ability to provide a painless and convenient process. In this review article, we summarized the most recent development of microneedles, and we started by classifying various microneedle systems, advantages, and fundamental properties. Subsequently, it provides a comprehensive overview of different types of microneedles, the material used to fabricate microneedles, the fundamental properties of ideal microneedles, and their applications in tissue engineering and regenerative medicine, primarily focusing on preserving and restoring impaired tissues and organs. The limitations and perspectives have been discussed by concluding their future therapeutic applications in tissue engineering and regenerative medicines.

Hollow microneedles for ocular drug delivery

Microneedles (MNs) are micron-sized needles, typically <2 mm in length, arranged either as an array or as single needle. These MNs offer a minimally invasive approach to ocular drug delivery due to their micron size (reducing tissue damage compared to that of hypodermic needles) and overcoming significant barriers in drug administration. While various types of MNs have been extensively researched, significant progress has been made in the use of hollow MNs (HMNs) for ocular drug delivery, specifically through suprachoroidal injections. The suprachoroidal space, situated between the sclera and choroid, has been targeted using optical coherence tomography-guided injections of HMNs for the treatment of uveitis. Unlike other MNs, HMNs can deliver larger volumes of formulations to the eye. This review primarily focuses on the use of HMNs in ocular drug delivery and explores their ocular anatomy and the distribution of formulations following potential HMN administration routes. Additionally, this review focuses on the influence of formulation characteristics (e.g., solution viscosity, particle size), HMN properties (e.g., bore or lumen diameter, MN length), and routes of administration (e.g., periocular transscleral, suprachoroidal, intravitreal) on the ocular distribution of drugs. Overall, this paper highlights the distinctive properties of HMNs, which make them a promising technology for improving drug delivery efficiency, precision, and patient outcomes in the treatment of ocular diseases.

An Innovative Polymeric Platform for Controlled and Localized Drug Delivery

Precision medicine aims to optimize pharmacological treatments by considering patients' genetic, phenotypic, and environmental factors, enabling dosages personalized to the individual. To address challenges associated with oral and injectable administration approaches, implantable drug delivery systems have been developed. These systems overcome issues like patient adherence, bioavailability, and first-pass metabolism. Utilizing new combinations of biodegradable polymers, the proposed solution, a Polymeric Controlled Release System (PCRS), allows minimally invasive placement and controlled drug administration over several weeks. This study's objective was to show that the PCRS exhibits a linear biphasic controlled release profile, which would indicate potential as an effective treatment vehicle for cervical malignancies. An injection mold technique was developed for batch manufacturing of devices, and in vitro experiments demonstrated that the device's geometry and surface area could be varied to achieve various drug release profiles. This study's results motivate additional development of the PCRS to treat cervical cancer, as well as other malignancies, such as lung, testicular, and ovarian cancers.

Facile Fabrication of Silk Fibroin/Off-Stoichiometry Thiol-Ene (OSTE) Microneedle Array Patches

Microneedles have been used in various applications in biomedical engineering, including drug delivery, biosensing, and vaccine delivery. In this study, we develop a novel protocol to fabricate silk fibroin/off-stoichiometry thiol-ene (OSTE) hybrid microneedle array patches. Silk fibroin, as a natural biomaterial, has been proven to be suitable as a drug carrier. Firstly, drug (we use insulin in this experiment) dissolved in silk fibroin solution is deposited on a microneedle mold and dried thoroughly. After that, silk fibroin needle tips are formed on the OSTE base by replica molding. We investigated the influence of the silk fibroin concentration on the length of silk needle tips and found that the silk concentration had a small influence on the tip length. We also tested the mechanical strength of the microneedles by inserting them into gelatin gel for dummy drug delivery tests. Such composite structures have the potential to increase the delivery efficiency by delivering the whole silk tip into the dermis.

Solid Fiber Inside of Capillary and Modified Fusion-Spliced Fiber Optic Microneedle Devices for Improved Light Transmission Efficiency

Convection-enhanced delivery (CED) is a drug delivery technique used to deliver therapeutics directly to the brain and is a continually evolving technique to treat glioblastoma. Early versions of CED have proven to result in inadequate drug volume dispersed (Vd), increasing the likelihood of tumor recurrence. Fiber optic microneedle devices (FMDs) with the ability to deliver fluid and thermal energy simultaneously have shown an ability to increase Vd, but FMDs have historically had low light transmission efficiency. In this study, we present a new fabrication method, solid fiber inside capillary (SFIC) FMD, and a modified fusion splicing (FS) method with the goal of increasing light delivery efficiency. The modified FS FMD resulted in an increase in light transmission efficiency between 49% and 173% compared to previous prototypes. However, the FS FMD resulted in significantly lower transmission efficiencies compared to the SFIC FMD (p ≤ 0.04) and FS FMDs perform much worse when light-absorptive materials, like black dye, are placed in the bore. The light absorption of a candidate cytotoxic agent, QUAD-CTX, appear to be similar to water, and light delivery through FS FMDs filled with QUAD-CTX achieves a transmission efficiency of 85.6 ± 5.4%. The fabrication process of the SFIC FMDs results in extremely fragile FMDs. Therefore, the use of a modified FS FMD fabrication process appears to be better suited for balancing the desire to increase light transmission efficiency while retaining a sturdy FMD construction.

Advances in bioengineering pancreatic tumor-stroma physiomimetic Biomodels

Pancreatic cancer exhibits a unique bioarchitecture and desmoplastic cancer-stoma interplay that governs disease progression, multi-resistance, and metastasis. Emulating the biological features and microenvironment heterogeneity of pancreatic cancer stroma in vitro is remarkably complex, yet highly desirable for advancing the discovery of innovative therapeutics. Diverse bioengineering approaches exploiting patient-derived organoids, cancer-on-a-chip platforms, and 3D bioprinted living constructs have been rapidly emerging in an endeavor to seamlessly recapitulate major tumor-stroma biodynamic interactions in a preclinical setting. Gathering on this, herein we showcase and discuss the most recent advances in bio-assembling pancreatic tumor-stroma models that mimic key disease hallmarks and its desmoplastic biosignature. A reverse engineering perspective of pancreatic tumor-stroma key elementary units is also provided and complemented by a detailed description of biodesign guidelines that are to be considered for improving 3D models physiomimetic features. This overview provides valuable examples and starting guidelines for researchers envisioning to engineer and characterize stroma-rich biomimetic tumor models. All in all, leveraging advanced bioengineering tools for capturing stromal heterogeneity and dynamics, opens new avenues toward generating more predictive and patient-personalized organotypic 3D in vitro platforms for screening transformative therapeutics targeting the tumor-stroma interplay.

Characterization of thermal and optical properties in porcine pancreas tissue

BACKGROUND

Photothermal therapies have shown promise for treating pancreatic ductal adenocarcinoma when they can be applied selectively, but off-target heating can frustrate treatment outcomes. Improved strategies leveraging selective binding and localized heating are possible with precision medical approaches such as functionalized gold nanoparticles, but careful control of optical dosage and thermal generation would be imperative. However, the literature review revealed many groups assume liver properties for pancreas tissue or rely on insufficiently rigorous characterization studies.

OBJECTIVE

The objective of this study was to determine the thermal conductivity and optical properties at 808/1064 nm wavelengths in healthy samples of fresh and frozen porcine pancreas ex vivo.

METHODS

Thermal conductivity of the porcine pancreas tissue was measured by utilizing a hot plate and two K-type thermocouples. Experimental variables such as tissue sample thickness, hot plate temperature, and heat convection coefficient were estimated through the control experiments utilizing specimens with known thermal conductivity. Optical evaluations assessed light attenuation at the 808 and 1064 nm wavelengths (continuous wave, collimated beam) by measuring the light transmittance and reflectance of different tissue thicknesses. In turn, these measurements were input into an inverse adding-doubling program to estimate the optical absorption and reduced scattering coefficients.

RESULTS

Interestingly, pancreas tissue thermal conductivity was demonstrated to have no significant difference (p > 0.5) between samples that were fresh, frozen for 7 days, or frozen for 14 days. Conversely, optical property assessment exhibited a significant difference (p < 0.001) between fresh and frozen tissue samples, with increased absorbance and reflectance within the frozen group. However, the optical attenuation values measured were substantially less than that of the liver or reported in previous pancreas studies, suggesting a wide overestimation of these properties.

CONCLUSIONS

These thermal and optical properties are critical to the development of novel therapeutic strategies like plasmonic photothermal therapy, but perhaps more importantly, are invaluable towards informing better surgical planning and operative technique among the existing thermal approaches for treating pancreas tissue.

Assessment and Modeling of Plasmonic Photothermal Therapy Delivered via a Fiberoptic Microneedle Device Ex Vivo

Plasmonic photothermal therapy (PPTT) has potential as a superior treatment method for pancreatic cancer, a disease with high mortality partially attributable to the currently non-selective treatment options. PPTT utilizes gold nanoparticles infused into a targeted tissue volume and exposed to a specific light wavelength to induce selective hyperthermia. The current study focuses on developing this approach within an ex vivo porcine pancreas model via an innovative fiberoptic microneedle device (FMD) for co-delivering light and gold nanoparticles. The effects of laser wavelengths (808 vs. 1064 nm), irradiances (20-50 mW·mm-2), and gold nanorod (GNR) concentrations (0.1-3 nM) on tissue temperature profiles were evaluated to assess and control hyperthermic generation. The GNRs had a peak absorbance at ~800 nm. Results showed that, at 808 nm, photon absorption and subsequent heat generation within tissue without GNRs was 65% less than 1064 nm. The combination of GNRs and 808 nm resulted in a 200% higher temperature rise than the 1064 nm under similar conditions. A computational model was developed to predict the temperature shift and was validated against experimental results with a deviation of <5%. These results show promise for both a predictive model and spatially selective, tunable treatment modality for pancreatic cancer.

Characterizing and Tuning Perfusion Parameters Within an Innovative, Versatile Oxygenating Perfusion System

The advantages of oxygenated perfusion are continuing to be demonstrated by many groups focused on improving the efficacy of tissue preservation for transplant, bioreactors for studies of basic tissue physiology, and closed-loop resuscitation. This work presents a novel and portable device that supplies oxygenated and pulsatile perfusion, both of which are regulated by a single pump-oxygenator component comprised of silicone tubes that are cyclically inflated/deflated with compressed oxygen. In this study, pump variables (oxygen supply pressure and length of a silicone tube) were evaluated against hydraulic elements that mimicked the vascular resistance of kidneys, livers, and hearts. The perfusion pressures, flow rates, and oxygenation rates produced by the device were characterized for all configurations of pump variables, and the pulse rates were tuned to improve performance. The device supplied perfusion pressures ranging from 3.5 to 109 mmHg, flow rates ranging from 1.4 to 71.8 mL min^-1, and oxygenation rates up to 316.6 µmol min^-1. From those results, it was determined that the device was capable of achieving perfusion parameters used in previous kidney, liver, and heart preservation studies. Ultimately, this research demonstrated the efficacy of a novel device that is designed to supply oxygenated perfusion across a range of applications.