Amphiphilic Block Copolymer Microspheres Derived from Castor Oil, Poly(ε-carpolactone), and Poly(ethylene glycol): Preparation, Characterization and Application in Naltrexone Drug Delivery

Protein-polymer bioconjugation, immobilization, and encapsulation: a comparative review towards applicability, functionality, activity, and stability

Polymer-based biomaterials have received a lot of attention due to their biomedical, agricultural, and industrial potential. Soluble protein-polymer bioconjugates, immobilized proteins, and encapsulated proteins have been shown to tune enzymatic activity, improved pharmacokinetic ability, increased chemical and thermal stability, stimuli responsiveness, and introduced protein recovery. Controlled polymerization techniques, increased protein-polymer attachment techniques, improved polymer surface grafting techniques, controlled polymersome self-assembly, and sophisticated characterization methods have been utilized for the development of well-defined polymer-based biomaterials. In this review we aim to provide a brief account of the field, compare these methods for engineering biomaterials, provide future directions for the field, and highlight impacts of these forms of bioconjugation.

New Biodegradable Poly(l-lactide)-Block-Poly(propylene adipate) Copolymer Microparticles for Long-Acting Injectables of Naltrexone Drug

In the present study, novel block copolymers of poly(l-lactide)-block-poly(propylene adipate) (PLLA-b-PPAd) were synthesized in two ratios, 90/10 and 75/25 w/w and were further investigated as long-acting injectable (LAI) polymeric matrices in naltrexone base microparticle formulations. The synthesized polymers were characterized by 1H-NMR, 13C-NMR, FTIR, XRD, TGA and DSC. NMR and FTIR spectroscopies confirmed the successful synthesis of copolymers while DSC showed that these are block copolymers with well-defined and separated blocks. Microparticles were prepared by single emulsification method and were further characterized. Nanoparticles in the range of 0.4-4.5 μm were prepared as indicated by SEM, with copolymers giving the lowest particle size. By XRD and DSC it was found that naltrexone was present in the amorphous state in its microparticles. Dissolution study showed a drug release extending over seven days, indicating that these novel PLLA-b-PPAd copolymers could be promising matrices for naltrexone's LAI formulations. It was evidenced that drug release depended on the copolymer composition. Model release studies showed that drug release is controlled by diffusion.

Paclitaxel Magnetic Core⁻Shell Nanoparticles Based on Poly(lactic acid) Semitelechelic Novel Block Copolymers for Combined Hyperthermia and Chemotherapy Treatment of Cancer

Magnetic hybrid inorganic/organic nanocarriers are promising alternatives for targeted cancer treatment. The present study evaluates the preparation of manganese ferrite magnetic nanoparticles (MnFe₂O₄ MNPs) encapsulated within Paclitaxel (PTX) loaded thioether-containing ω-hydroxyacid-co-poly(d,l-lactic acid) (TEHA-co-PDLLA) polymeric nanoparticles, for the combined hyperthermia and chemotherapy treatment of cancer. Initially, TEHA-co-PDLLA semitelechelic block copolymers were synthesized and characterized by ¹H-NMR, FTIR, DSC, and XRD. FTIR analysis showed the formation of an ester bond between the two compounds, while DSC and XRD analysis showed that the prepared copolymers were amorphous. MnFe₂O₄ MNPs of relatively small crystallite size (12 nm) and moderate saturation magnetization (64 emu·g⁻¹) were solvothermally synthesized in the sole presence of octadecylamine (ODA). PTX was amorphously dispersed within the polymeric matrix using emulsification/solvent evaporation method. Scanning electron microscopy along with energy-dispersive X-ray spectroscopy and transmission electron microscopy showed that the MnFe₂O₄ nanoparticles were effectively encapsulated within the drug-loaded polymeric nanoparticles. Dynamic light scattering measurements showed that the prepared nanoparticles had an average particle size of less than 160 nm with satisfactory yield and encapsulation efficiency. Diphasic PTX in vitro release over 18 days was observed while PTX dissolution rate was mainly controlled by the TEHA content. Finally, hyperthermia measurements and cytotoxicity studies were performed to evaluate the magnetic response, as well as the anticancer activity and the biocompatibility of the prepared nanocarriers.

Preparation and characterization of Alendronate depot microspheres based on novel poly(-ε-caprolactone)/Vitamin E TPGS copolymers

In the present study, new aledronate (AL) loaded microspheres were prepared with the use of polycaprolactone (PCL)/Vitamin E d-ɑ-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS) copolymers. Specifically, PCL-TPGS copolymers, prepared at several PCL to TPGS ratios (namely, 90/10, 80/20, 70/30 and 60/40 w/w) via a ring opening polymerization process, were characterized by intrinsic viscosity, proton nuclear magnetic resonance (¹H NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and enzymatic hydrolysis. Results showed that as TPGS content increases the intrinsic viscosity of the copolymer (and hence, the viscosity-average molecular weight) is decreasing, while FTIR analysis showed the formation of hydrogen bonds between the —C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]>O of PCL and the —OH of TPGS. Additionally, XRD analysis indicated that the prepared copolymers were semi-crystalline in nature, while enzymatic hydrolysis studies showed that increasing TGPS content led to increasing copolymer hydrolysis. In the following step, AL drug-loaded microspheres were prepared via single emulsification process. Scanning electron microscopy (SEM) revealed the formation of coarse drug-loaded microspheres with particle size close to 5 μm, while XRD analysis showed that the API was amorphously dispersed only in the cases of high TPGS content. Furthermore, FTIR analysis showed that the API did not interact with the copolymer components, while in vitro drug release studies showed that increasing PCL content led to decreasing API release rate. Finally, analysis of the drug release profiles suggested that the API release mechanism was solely governed by the polymer matrix erosion.

Targeted Drug Delivery from Titanium Implants: A Review of Challenges and Approaches

Titanium implants are considered the gold standard of treatment for dental and orthopedic applications. Biocompatibility, low elasticity, and corrosion resistance are some of the key properties of these metallic implants. Nonetheless, a long-term clinical failure of implants may occur due to inadequate osseointegration. Poor osseointegration induces mobility, inflammation, increased bone resorption, and osteolysis; hence, it may result in painful revision surgeries. Topographical modifications, improvement in hydrophilicity, and the development of controlled-release drug-loading systems have shown to improve cellular adhesion, proliferation, and differentiation. Surface modifications, along with drug coating, undoubtedly demonstrate better osseointegration, especially in challenged degenerative conditions, such as osteoporosis, osteoarthritis, and osteogenesis imperfecta. Anabolic bone-acting drugs, such as parathyroid hormone peptides, simvastatin, prostaglandin-EP4-receptor antagonist, vitamin D, strontium ranelate, and anti-catabolic bone-acting drugs, such as calcitonin, bisphosphonates, and selective estrogen receptor modulators, expedite the process of osseointegration. In addition, various proteins, peptides, and growth factors may accessorize the idea of localized therapy. Loading these substances on modified titanium surfaces is achieved commonly by mechanisms such as direct coating, adsorption, and incorporating in biodegradable polymers. The primary approach toward the optimum drug loading is a critical trade-off between factors preventing release of a drug immediately and those allowing slow and sustained release. Recent advances broaden the understanding of the efficacy of adsorption, hydrogel coating, and electrospinning layer-by-layer coating facilitated by differential charge on metallic surface. This review discusses the existing approaches and challenges for the development of stable and sustained drug delivery systems on titanium implants, which would promote faster and superior osseointegration.