Coiled-Coil Protein Hydrogels Engineered with Minimized Fiber Diameters for Sustained Release of Doxorubicin in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) lacks expressed protein targets, making therapy development challenging. Hydrogels offer a promising new route in this regard by improving the chemotherapeutic efficacy through increased solubility and sustained release. Moreover, subcutaneous hydrogel administration reduces patient burden by requiring less therapy and shorter treatment times. We recently established the design principles for the supramolecular assembly of single-domain coiled-coils into hydrogels. Using a modified computational design algorithm, we designed Q8, a hydrogel with rapid assembly for faster therapeutic hydrogel preparation. Q8 encapsulates and releases doxorubicin (Dox), enabling localized sustained release via subcutaneous injection. Remarkably, a single subcutaneous injection of Dox-laden Q8 (Q8•Dox) significantly suppresses tumors within just 1 week. This work showcases the bottom-up engineering of a fully protein-based drug delivery vehicle for improved TBNC treatment via noninvasive localized therapy.

Fabrication and Characterisation of 3D-Printed Triamcinolone Acetonide-Loaded Polycaprolactone-Based Ocular Implants

Triamcinolone acetonide (TA) is a corticosteroid that has been used to treat posterior segment eye diseases. TA is injected intravitreally in the management of neovascular disorders; however, frequent intravitreal injections result in many potential side effects and poor patient compliance. In this work, a 3D bioprinter was used to prepare polycaprolactone (PCL) implants loaded with TA. Implants were manufactured with different shapes (filament-, rectangular-, and circle-shaped) and drug loadings (5, 10, and 20%). The characterisation results showed that TA was successfully mixed and incorporated within the PCL matrix without using solvents, and drug content reached almost 100% for all formulations. The drug release data demonstrate that the filament-shaped implants (SA/V ratio~7.3) showed the highest cumulative drug release amongst all implant shapes over 180 days, followed by rectangular- (SA/V ratio~3.7) and circle-shaped implants (SA/V ratio~2.80). Most implant drug release data best fit the Korsmeyer−Peppas model, indicating that diffusion was the prominent release mechanism. Additionally, a biocompatibility study was performed; the results showed >90% cell viability, thus proving that the TA-loaded PCL implants were safe for ocular application.

Effect of Divalent Metal Cations on the Conformation, Elastic Behavior, and Controlled Release of a Photocrosslinked Protein Engineered Hydrogel

We investigate the effect of Zn²⁺, Cu²⁺, and Ni²⁺ coordination on the conformation, mechanical properties, contraction, and small-molecule drug encapsulation and release of a photocrosslinked protein-engineered hydrogel, CEC-D. The treatment of the CEC-D hydrogel with divalent metal (M²⁺) results in significant conformational changes where a loss in structure is observed with Zn²⁺, while both Cu²⁺ and Ni²⁺ induce a blueshift. The relationship of M²⁺ to mechanical properties illustrates a trend, while the CEC-D hydrogel in the presence of 2 mM Cu²⁺ reveals the highest increase in G' to 14.4 ± 0.7 kPa followed by 9.7 ± 0.9 kPa by addition of 2 mM Zn²⁺, and a decrease to 1.1 ± 0.2 kPa is demonstrated in the presence of 2 mM Ni²⁺. A similar observation in M²⁺ responsiveness emerges where CEC-D hydrogels contract into a condensed state of 2.6-fold for Cu²⁺, 2.4-fold for Zn²⁺, and 1.6-fold for Ni²⁺. Furthermore, CEC-D hydrogels coordinated with M²⁺ demonstrate control over the encapsulation and release of the small molecule curcumin. The trend of release is opposite of the mechanical and contraction properties with a 70.0 ± 5.3% release with Ni²⁺, 64.2 ± 1.2% release with Zn²⁺, and 42.3 ± 11.3 release with Cu²⁺. Taken together, these results indicate that the CEC-D hydrogel tuned by M²⁺ is a promising drug delivery platform with tunable physicochemical properties.

Free-Standing Photocrosslinked Protein Polymer Hydrogels for Sustained Drug Release

The fabrication of protein hydrogels consisting of different properties and functional motifs is critical in the development of protein-based materials for biomedical applications. Here, we report the design and characterization of a triblock protein polymer, CEC, composed of two different self-assembling domains derived from elastin protein (E) and coiled-coil protein (C), photopolymerized with a NHS-diazirine (D) crosslinker into a CEC-D hydrogel. The optimal photocrosslinker concentration and exposure time is determined to fabricate a free-standing hydrogel. Upon increasing the concentration of the CEC-D monomer and environmental temperature, the CEC-D hydrogel's conformation decreases in helical content from 58.0% to 44.8% and increases in β-content from 25.9% to 38.1%. These gels experience 55 ± 6% protein erosion from the free-standing gel in 13 days as the gel films gradually decrease in size. The swelling ratio of 12 ± 1% denotes that the gel has a swelling ability comparable to other protein hydrogels. These photocrosslinked CEC-D hydrogels can be employed for drug delivery with high encapsulation and 14 ± 2% release of curcumin into the supernatant in a week long study. Overall, the photocrosslinked CEC-D hydrogels exhibit stability, swelling ability, and sustained release of drug.

New Insight into the Mechanism of Drug Release from Poly(d,l-lactide) Film by Electron Paramagnetic Resonance

A novel approach based on convolution of the electron paramagnetic resonance (EPR) spectra was used for quantitative study of the release kinetics of paramagnetic dopants from poly(d,l-lactide) films. A non-monotonic dependence of the release rate on time was reliably recorded. The release regularities were compared with the dynamics of polymer structure changes determined by EPR, SEM, and optic microscopy. The data obtained allow for the conclusion that the main factor governing dopant release is the formation of pores connected with the surface. In contrast, the contribution of the dopant diffusion through the polymer matrix is negligible. The dopant release can be divided into two phases: release through surface pores, which are partially closed with time, and release through pores initially formed inside the polymer matrix due to autocatalytic hydrolysis of the polymer and gradually connected to the surface of the sample. For some time, these processes co-occur. The mathematical model of the release kinetics based on pore formation is presented, describing the kinetics of release of various dopants from the polymer films of different thicknesses.

Release mechanisms and applications of drug delivery systems for extended-release

INTRODUCTION

Drug delivery systems with extended-release profiles are ideal in improving patient compliance with enhanced efficacy. To develop devices capable of a prolonged delivery kinetics, it is crucial to understand the various underlying mechanisms contributing to extended drug release and the impact thereof on modulating the long-term performance of such systems in a practical application environment.

AREAS COVERED

This review article intends to provide a comprehensive summary of release mechanisms in extended-release drug delivery systems, particularly polymer-based systems; however, other material types will also be mentioned. Selected current research in the delivery of small molecule drugs and macromolecules is highlighted. Emphasis is placed on the combined impact of different release mechanisms and drug properties on the long-term release kinetics in vitro and in vivo.

EXPERT OPINION

The development of drug delivery systems over an extended duration is promising but also challenging when considering the numerous interrelated delivery-related parameters. Achieving a well-controlled extended drug release requires advanced techniques to minimize burst release and lag phase, a better understanding of the dynamic interrelationship between drug properties and release profiles over time, and a thorough elucidation of the impact of multiple in vivo conditions to methodically evaluate the eventual clinical efficacy.

Poly(glycerol sebacate) nanoparticles for ocular delivery of sunitinib: physicochemical, cytotoxic and allergic studies

Poly(glycerol sebacate) (PGS) is a new biodegradable polymer with good biocompatibility used in many fields of biomedicine and drug delivery. Sunitinib-loaded PGS/gelatine nanoparticles were prepared by the de-solvation method for retinal delivery and treatment of diabetic retinopathy. The nanoparticles were characterised by Fourier-transform infrared and differential scanning calorimetry. The effects of different formulation variables including drug-to-carrier ratio, gelatine-to-PGS ratio, and glycerine-to-sebacate ratio were assessed on the encapsulation efficiency (EE%), particle size, release efficiency (RE), and zeta potential of the nanoparticles. The in vitro cytotoxicity of PGS/gelatine nanoparticles was studied on L929 cells. Draize test on rabbit eyes was also done to investigate the possible allergic reactions caused by the polymer. Glycerine/sebacic acid was the most effective parameter on the EE and RE. Gelatine-to-PGS ratio had the most considerable effect on the particle size while the RE was more affected by the glycerine/sebacic acid ratio. The optimised formulation (S₁G_0.7D_21.2) exhibited a particle size of 282 nm, 34.6% EE, zeta potential of -8.9 mV, and RE% of about 27.3% for drug over 228 h. The 3-(4,5-dimethylthuazol-2-yl)-2,5-diphenyltetrazolium bromide assay indicated PGS/gelatine nanoparticles were not cytotoxic and sunitinib-loaded nanoparticles were not toxic at concentrations <36 nM.

Dynamic release of gentamicin sulfate (GS) from alginate dialdehyde (AD)-crosslinked casein (CAS) films for antimicrobial applications

In the present work, antibiotic drug gentamicin sulfate (GS) has been loaded into alginate dialdehyde-crosslinked casein (CAS) films for wound dressing applications. The films have been characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy. The dynamic release of model drug GS has been investigated in the physiological fluid at 37 °C. The drug release data has been interpreted in the terms of various kinetic models such as Power function model, first order model and Schott model. The release data was found to be well fitted by Schott model. The various diffusion coefficients are also evaluated. The adsorption of model therapeutic protein BSA on the film has been investigated. The maximum adsorption is found to be 5.7 mg/cm2.The films were tested for their antibacterial and anti-fungal action. Finally, the in vivo wound healing study was carried out on Albino wistar rats.