Role of Electrostatic Interactions on the Transport of Druglike Molecules in Hydrogel-Based Articular Cartilage Mimics: Implications for Drug Delivery

Development of UV-Vis Imaging Compatible Chromatographic Matrix with Application for Injectable Formulation Characterization

Transport within human tissue matrices, e.g., the subcutaneous tissue, exhibits some resemblance to chromatographic processes. Here, a porous matrix comprising agarose beads compatible with UV-vis imaging was developed for a parallel piped rectangular flow cell (4 mm light path). Introduction of high-molecular weight dextrans (Mr ∼ 200000 and ∼500000) at 10% (w/v) rendered imaging possible by providing optical clearing of the turbid porous matrix, resulting in improved transmittance as well as resolution (from 400 to 180 μm) at 280 nm, as well as 520 nm. The interplay between diffusive and convective transport at 0 < Pe ≤ 28 was visualized at 280 nm upon injection of dexamethasone suspensions. Real-time UV-vis imaging showed in-flow cell the effect of incorporating ion-exchange resins on the retention of infliximab, lysozyme, and α-lactalbumin. The ion-exchange matrix may serve as a surrogate for polyelectrolytes in the subcutaneous tissue, assessing the potential role of electrostatic interactions of biotherapeutics upon injection. UV-vis imaging of size-exclusion chromatographic matrixes may be of interest in its own right and potentially develop into a characterization tool for injectables.

Investigation of Lysozyme Diffusion in Agarose Hydrogels Employing a Microfluidics-Based UV Imaging Approach

Hydrogels are polymer-based materials with a high water content. Due to their biocompatible and cell-friendly nature, they play a major role in a variety of biotechnological applications. For many of these applications, diffusibility is an essential property influencing the choice of material. We present an approach to estimate diffusion coefficients in hydrogels based on absorbance measurements of a UV area imaging system. A microfluidic chip with a y-junction was employed to generate a fluid-hydrogel interface and the diffusion of lysozyme from the fluid into the hydrogel phase was monitored. Employing automated image and data processing, analyte concentration profiles were generated from the absorbance measurements and fits with an analytical solution of Fick’s second law of diffusion were applied to estimate diffusion coefficients. As a case study, the diffusion of lysozyme in hydrogels made from different concentrations (0.5–1.5% (w/w)) of an unmodified and a low-melt agarose was investigated. The estimated diffusion coefficients for lysozyme were between 0.80 ± 0.04×10−10 m2 s−1 for 1.5% (w/w) low-melt agarose and 1.14 ± 0.02×10−10 m2 s−1 for 0.5% (w/w) unmodified agarose. The method proved sensitive enough to resolve significant differences between the diffusion coefficients in different concentrations and types of agarose. The microfluidic approach offers low consumption of analyte and hydrogel and requires only relatively simple instrumentation.

Application of UV dissolution imaging to pharmaceutical systems

UV-vis spectrometry is widely used in the pharmaceutical sciences for compound quantification, alone or in conjunction with separation techniques, due to most drug entities possessing a chromophore absorbing light in the range 190-800 nm. UV dissolution imaging, the scope of this review, generates spatially and temporally resolved absorbance maps by exploiting the UV absorbance of the analyte. This review aims to give an introduction to UV dissolution imaging and its use in the determination of intrinsic dissolution rates and drug release from whole dosage forms. Applications of UV imaging to non-oral formulations have started to emerge and are reviewed together with the possibility of utilizing UV imaging for physical chemical characterisation of drug substances. The benefits of imaging drug diffusion and transport processes are also discussed.

Thermo-responsive injectable naringin-loaded hydrogel polymerised sodium alginate/bioglass delivery for articular cartilage

In the human body, joint cartilage is of great importance. It has long been a big therapeutic problem to fix joint cartilage lesions as it appears due to different conditions. Recent stories have shown that the cartilage replacement process must delay the extracellular (ECM) cartilage deterioration and modulate the host's inflammation response. For the reconstruction of the articular cartilage, drug-loaded injectable hydrogels were developed. This hydrogel could retain the chondrocyte phenotype, but the host's inflammatory reaction could also be controlled. The bioglass (BG)/sodium alginate (SA) injectable hydrogels was combined with agarose (AG)/Naringin hydrogel in injectable thermal response for articular cartilage regeneration with a non-chargeable hydrogel that contains both Naringin and BG (Naringin–BG hydrogels). The Naringin–BG hydrogel has an adequate swelling ratio that encourages the fusion of tissue formed with host tissue and enables the gradual release of Naringin bioavailabilities enhanced in situ. The Naringin–BG hydrogel can upgrade the typical chondrocyte phenotype by upregulating aggrecan, SRY-box 9, and collagen type II alpha one chain. It may also stimulate the polarization of M2 macrophage, lower inflammations, and prevent ECM degradations through the decrease of the expressions of the indictable metalloproteinase-13 matrix, nitric oxide synthase, and metalloproteinase-1 matrix. The formed tissues were identical to normal tissues and firmly incorporated with the surrounding tissue after administering the Naringin–BG hydrogels into the rat model articular cartilage defects. Then the injectable Naringin–BG hydrogel increases the bioavailable content of Naringin and retains the chondrocyte phenotype.

Glutathione-Conjugated Hydrogels: Flexible Vehicles for Personalized Treatment of Bacterial Infections

PURPOSE

Skin and soft tissue infections are increasingly prevalent and often complicated by potentially fatal therapeutic hurdles, such as poor drug perfusion and antibiotic resistance. Delivery vehicles capable of versatile loading may improve local bioavailability and minimize systemic toxicities yet such vehicles are not clinically available. Therefore, we aimed to expand upon the use of glutathione-conjugated poly(ethylene glycol) GSH-PEG hydrogels beyond protein delivery and evaluate the ability to deliver traditional therapeutic molecules.

METHODS

PEG and GSH-PEG hydrogels were prepared using ultraviolet light (UV)-polymerization. Hydrogel loading and release of selected drug candidates was examined using UV-visible spectrometry. Therapeutic molecules and GST-fusion protein loading was examined using UV-visible and fluorescent spectrometry. Efficacy of released meropenem was assessed against meropenem-sensitive and -resistant P. aeruginosa in an agar diffusion bioassay.

RESULTS

For all tested agents, GSH-PEG hydrogels demonstrated time-dependent loading whereas PEG hydrogels did not. GSH-PEG hydrogels released meropenem over 24 h. Co-loading of biologic and traditional therapeutics into a single vehicle was successfully demonstrated. Meropenem-loaded GSH-PEG hydrogels inhibited the growth of meropenem-sensitive and resistant P. aeruginosa isolates.

CONCLUSION

GSH ligands within GSH-PEG hydrogels allow loading and effective delivery of charged therapeutic agents, in addition to biologic therapeutics.

Enhanced In Vitro and In Vivo Efficacy of Alginate/Silk Protein/Hyaluronic Acid with Polypeptide Microsphere Delivery for Tissue Regeneration of Articular Cartilage

Alginate/Silk fibroin/hyaluronic acid (ALG/SF/HA) nanocomposites were synthesised using blending, inter-linking, and lyophilization methods. We investigated the physicochemical properties of the resulting nanocomposites, including their water retention, weight loss, porosity and cytocompatibility. The optimum ratios of the ALG/SF/HA scaffolding were 3:6.5:0.5. Nanocomposites with optimum ratios were then prepared by integrating pilose antler polypeptides (PAPS) to poly(lactic-co-glycolic acid) (PLGA) microspheres, and the performance was investigated. PAPS-ALG/SF/HA nanocomposites exhibited desirable adhesions and proliferations. Rabbit cartilage deficiencies was developed by the animal model. The cartilage repair effects deficiencies were detected and analyzed between PAPS-SF/ALG/ALG/SF/HA, and control activity classes. The deficiencies were virtually fully remedied after 13 weeks in the presence of PAPS-ALG/SF/HA class, suggesting that the PAPS-ALG/SF/HA nanocomposites had a positive effects on joint cartilage repair.

UV imaging in pharmaceutical analysis

UV imaging provides spatially and temporally resolved absorbance measurements, which are highly useful in pharmaceutical analysis. Commercial UV imaging instrumentation was originally developed as a detector for separation sciences, but the main use is in the area of in vitro dissolution and release testing studies. The review covers the basic principles of the technology and summarizes the main applications in relation to intrinsic dissolution rate determination, excipient compatibility studies and in vitro release characterization of drug substances and vehicles intended for parenteral administration. UV imaging has potential for providing new insights to drug dissolution and release processes in formulation development by real-time monitoring of swelling, precipitation, diffusion and partitioning phenomena. Limitations of current instrumentation are discussed and a perspective to new developments and opportunities given as new instrumentation is emerging.

Application of UV Imaging in Formulation Development

Efficient drug delivery is dependent on the drug substance dissolving in the body fluids, being released from dosage forms and transported to the site of action. A fundamental understanding of the interplay between the physicochemical properties of the active compound and pharmaceutical excipients defining formulation behavior after exposure to the aqueous environments and pharmaceutical performance is critical in pharmaceutical development, manufacturing and quality control of drugs. UV imaging has been explored as a tool for qualitative and quantitative characterization of drug dissolution and release with the characteristic feature of providing real-time visualization of the solution phase drug transport in the vicinity of the formulation. Events occurring during drug dissolution and release, such as polymer swelling, drug precipitation/recrystallization, or solvent-mediated phase transitions related to the structural properties of the drug substance or formulation can be monitored. UV imaging is a non-intrusive and simple-to-operate analytical technique which holds potential for providing a mechanistic foundation for formulation development. This review aims to cover applications of UV imaging in the early and late phase pharmaceutical development with a special focus on the relation between structural properties and performance. Potential areas of future advancement and application are also discussed.