Thermosensitive Polyester Hydrogel for Application of Immunosuppressive Drug Delivery System in Skin Allograft

Tacrolimus-loaded Drug Delivery Systems in Vascularized Composite Allotransplantation: Lessons and Opportunities for Local Immunosuppression

Long-term systemic immunosuppression is needed for vascularized composite allotransplantation (VCA). The high rate of acute rejection episodes in the first posttransplant year, the development of chronic rejection, and the adverse effects that come along with this treatment, currently prevent a wider clinical application of VCA. Opportunistic infections and metabolic disturbances are among the most observed side effects in VCA recipients. To overcome these challenges, local immunosuppression using biomaterial-based drug delivery systems (DDS) have been developed. The aim of these systems is to provide high local concentrations of immunosuppressive drugs while reducing their systemic load. This review provides a summary of recently investigated local DDS with different mechanisms of action such as on-demand, ultrasound-sensitive, or continuous drug delivery. In preclinical models, ranging from rodent to porcine and nonhuman primate models, this approach has been shown to reduce systemic tacrolimus (TAC) load and adverse effects, while prolonging graft survival. Localized immunosuppression using biomaterial-based DDS represents an encouraging approach to enhance graft survival and reduce toxic side effects of immunosuppressive drugs in VCA patients. Preclinical models using TAC-releasing DDS have demonstrated high local immunosuppressive effects with a low systemic burden. However, to reduce acute rejection events in translational animal models or in the clinical reality, the use of additional low-dose systemic TAC treatment may be envisaged. Patients may benefit through efficient graft immunosuppression and survival with negligible systemic adverse effects, resulting in better compliance and quality of life.

Thermosensitive Hydrogels as Targeted and Controlled Drug Delivery Systems: Potential Applications in Transplantation

Drug delivery in transplantation plays a vital role in promoting graft survival, preventing rejection, managing complications, and contributing to positive patient outcomes. Targeted and controlled drug delivery can minimize systemic effects. Thermosensitive hydrogels, due to their unique sol-gel transition properties triggered by thermo-stimuli, have attracted significant research interest as a potential drug delivery system in transplantation. This review describes the current status, characteristics, and recent applications of thermosensitive hydrogels for drug delivery. Studies aimed at improving allotransplantation outcomes using thermosensitive hydrogels are then elaborated on. Finally, the challenges and opportunities associated with their use are discussed. Understanding the progress of research will serve as a guide for future improvements in their application as a means of targeted and controlled drug delivery in translational therapeutic applications for transplantation.

A local drug delivery system prolongs graft survival by dampening T cell infiltration and neutrophil extracellular trap formation in vascularized composite allografts

Introduction

The standard treatment for preventing rejection in vascularized composite allotransplantation (VCA) currently relies on systemic immunosuppression, which exposes the host to well-known side effects. Locally administered immunosuppression strategies have shown promising results to bypass this hurdle. Nevertheless, their progress has been slow, partially attributed to a limited understanding of the essential mechanisms underlying graft rejection. Recent discoveries highlight the crucial involvement of innate immune components, such as neutrophil extracellular traps (NETs), in organ transplantation. Here we aimed to prolong graft survival through a tacrolimus-based drug delivery system and to understand the role of NETs in VCA graft rejection.

Methods

To prevent off-target toxicity and promote graft survival, we tested a locally administered tacrolimus-loaded on-demand drug delivery system (TGMS-TAC) in a multiple MHC-mismatched porcine VCA model. Off-target toxicity was assessed in tissue and blood. Graft rejection was evaluated macroscopically while the complement system, T cells, neutrophils and NETs were analyzed in graft tissues by immunofluorescence and/or western blot. Plasmatic levels of inflammatory cytokines were measured using a Luminex magnetic-bead porcine panel, and NETs were measured in plasma and tissue using DNA-MPO ELISA. Lastly, to evaluate the effect of tacrolimus on NET formation, NETs were induced in-vitro in porcine and human peripheral neutrophils following incubation with tacrolimus.

Results

Repeated intra-graft administrations of TGMS-TAC minimized systemic toxicity and prolonged graft survival. Nevertheless, signs of rejection were observed at endpoint. Systemically, there were no increases in cytokine levels, complement anaphylatoxins, T-cell subpopulations, or neutrophils during rejection. Yet, tissue analysis showed local infiltration of T cells and neutrophils, together with neutrophil extracellular traps (NETs) in rejected grafts. Interestingly, intra-graft administration of tacrolimus contributed to a reduction in both T-cellular infiltration and NETs. In fact, in-vitro NETosis assessment showed a 62-84% reduction in NETs after stimulated neutrophils were treated with tacrolimus.

Conclusion

Our data indicate that the proposed local delivery of immunosuppression avoids off-target toxicity while prolonging graft survival in a multiple MHC-mismatch VCA model. Furthermore, NETs are found to play a role in graft rejection and could therefore be a potential innovative therapeutic target.

Dual-Stimuli-Sensitive Smart Hydrogels Containing Magnetic Nanoparticles as Antitumor Local Drug Delivery Systems-Synthesis and Characterization

The aim of this study was to develop an innovative, dual-stimuli-responsive smart hydrogel local drug delivery system (LDDS), potentially useful as an injectable simultaneous chemotherapy and magnetic hyperthermia (MHT) antitumor treatment device. The hydrogels were based on a biocompatible and biodegradable poly(ε-caprolactone-co-rac-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-rac-lactide) (PCLA-PEG-PCLA, PCLA) triblock copolymer, synthesized via ring-opening polymerization (ROP) in the presence of a zirconium(IV) acetylacetonate (Zr(acac)4) catalyst. The PCLA copolymers were successfully synthesized and characterized using NMR and GPC techniques. Furthermore, the gel-forming and rheological properties of the resulting hydrogels were thoroughly investigated, and the optimal synthesis conditions were determined. The coprecipitation method was applied to create magnetic iron oxide nanoparticles (MIONs) with a low diameter and a narrow size distribution. The magnetic properties of the MIONs were close to superparamagnetic upon TEM, DLS, and VSM analysis. The particle suspension placed in an alternating magnetic field (AMF) of the appropriate parameters showed a rapid increase in temperature to the values desired for hyperthermia. The MIONs/hydrogel matrices were evaluated for paclitaxel (PTX) release in vitro. The release was prolonged and well controlled, displaying close to zero-order kinetics; the drug release mechanism was found to be anomalous. Furthermore, it was found that the simulated hyperthermia conditions had no effect on the release kinetics. As a result, the synthesized smart hydrogels were discovered to be a promising antitumor LDDS, allowing simultaneous chemotherapy and hyperthermia treatment.

Nanomedicine and nanoparticle-based delivery systems in plastic and reconstructive surgery

BACKGROUND

Nanotechnology and nanomedicine are rising novel fields in plastic and reconstructive surgery (PRS). The use of nanomaterials often goes with regenerative medicine. Due to their nanoscale, these materials stimulate repair at the cellular and molecular levels. Nanomaterials may be placed as components of nanocomposite polymers allowing enhancement of overall biochemical and biomechanical properties with improved scaffold properties, cellular attachment, and tissue regeneration. They may also be formulated as nanoparticle-based delivery systems for controlled release of signal factors or antimicrobials, for example. However, more studies on nanoparticle-based delivery systems still need to be done in this field. Nanomaterials are also used as frameworks for nerves, tendons, and other soft tissues.

MAIN BODY

In this mini-review, we focus on nanoparticle-based delivery systems and nanoparticles targeting cells for response and regeneration in PRS. Specifically, we investigate their roles in various tissue regeneration, skin and wound healing, and infection control. Cell surface-targeted, controlled-release, and inorganic nanoparticle formulations with inherent biological properties have enabled enhanced wound healing, tumor visualization/imaging, tissue viability, and decreased infection, and graft/transplantation rejection through immunosuppression.

CONCLUSIONS

Nanomedicine is also now being applied with electronics, theranostics, and advanced bioengineering technologies. Overall, it is a promising field that can improve patient clinical outcomes in PRS.

Thermo-Sensitive mPEG-PA-PLL Hydrogel for Drug Release of Calcitonin

The oral route is the most popular way of drug administration because of good patient compliance and ease of use. However, the oral delivery of peptides and proteins is difficult, mainly due to poor oral bioavailability. In past decades, researchers have developed several strategies to improve oral bioavailability by avoiding losing activity in the gastrointestinal (GI) tract and enhancing the intestinal permeability of these drugs. Methoxy poly(ethylene glycol)-poly(l-alanine) (mPEG-PA) is a thermo-sensitive hydrogel exhibiting a sol-to-gel phase transition property. This characteristic is appropriate for encapsulating peptide or protein drugs. To enhance the adhesion ability to intestinal mucus, a thermo-sensitive polymer, mPEG-PA, modified with charged amino acid lysine was developed. This positively charged material would help to bind the negatively charged mucin in mucus. The synthesis was conducted by individually synthesizing mPEG-PA and poly(l-lysine) (PLL) of different lengths via ring-opening polymerization. Then, mPEG-PA and PLL were combined using an NHS ester reaction to synthesize the triblock copolymer (mPEG-PA-PLL). Biocompatibility and the release of calcitonin from the synthesized hydrogel particles under different pH were examined. The initial data showed that the newly design material had a promising potential for the oral delivery of peptide drugs.

Implantable Immunosuppressant Delivery to Prevent Rejection in Transplantation

An innovative immunosuppressant with a minimally invasive delivery system has emerged in the biomedical field. The application of biodegradable and biocompatible polymer forms, such as hydrogels, scaffolds, microspheres, and nanoparticles, in transplant recipients to control the release of immunosuppressants can minimize the risk of developing unfavorable conditions. In this review, we summarized several studies that have used implantable immunosuppressant delivery to release therapeutic agents to prolong allograft survival. We also compared their applications, efficacy, efficiency, and safety/side effects with conventional therapeutic-agent administration. Finally, challenges and the future prospective were discussed. Collectively, this review will help relevant readers understand the different approaches to prevent transplant rejection in a new era of therapeutic agent delivery.