Self-assembly and drug release control of dual-responsive copolymers based on oligo(ethylene glycol)methyl ether methacrylate and spiropyran

Degradable Nanogels Based on Poly[Oligo(Ethylene Glycol) Methacrylate] (POEGMA) Derivatives through Thermo-Induced Aggregation of Polymer Chain and Subsequent Chemical Crosslinking

Polymer nanogels-considered as nanoscale hydrogel particles-are attractive for biological and biomedical applications due to their unique physicochemical flexibility. However, the aggregation or accumulation of nanoparticles in the body or the occurrence of the body's defense reactions still pose a research challenge. Here, we demonstrate the fabrication of degradable nanogels using thermoresponsive, cytocompatible poly[oligo(ethylene glycol) methacrylate]s-based copolymers (POEGMA). The combination of POEGMA's beneficial properties (switchable affinity to water, nontoxicity, non-immunogenicity) along with the possibility of nanogel degradation constitute an important approach from a biological point of view. The copolymers of oligo(ethylene glycol) methacrylates were partially modified with short segments of degradable oligo(lactic acid) (OLA) terminated with the acrylate group. Under the influence of temperature, copolymers formed self-assembled nanoparticles, so-called mesoglobules, with sizes of 140-1000 nm. The thermoresponsive behavior of the obtained copolymers and the nanostructure sizes depended on the heating rate and the presence of salts in the aqueous media. The obtained mesoglobules were stabilized by chemical crosslinking via thiol-acrylate Michael addition, leading to nanogels that degraded over time in water, as indicated by the DLS, cryo-TEM, and AFM measurements. Combining these findings with the lack of toxicity of the obtained systems towards human fibroblasts indicates their application potential.

Physically stimulus-responsive nanoparticles for therapy and diagnosis

Nanoparticles offer numerous advantages in various fields of science, particularly in medicine. Over recent years, the use of nanoparticles in disease diagnosis and treatments has increased dramatically by the development of stimuli-responsive nano-systems, which can respond to internal or external stimuli. In the last 10 years, many preclinical studies were performed on physically triggered nano-systems to develop and optimize stable, precise, and selective therapeutic or diagnostic agents. In this regard, the systems must meet the requirements of efficacy, toxicity, pharmacokinetics, and safety before clinical investigation. Several undesired aspects need to be addressed to successfully translate these physical stimuli-responsive nano-systems, as biomaterials, into clinical practice. These have to be commonly taken into account when developing physically triggered systems; thus, also applicable for nano-systems based on nanomaterials. This review focuses on physically triggered nano-systems (PTNSs), with diagnostic or therapeutic and theranostic applications. Several types of physically triggered nano-systems based on polymeric micelles and hydrogels, mesoporous silica, and magnets are reviewed and discussed in various aspects.

Molecular-Gated Drug Delivery Systems Using Light-Triggered Hydrophobic-to-Hydrophilic Switches

A photoresponsive molecular-gated drug delivery system (DDS) based on silicone-hydrogel (poly(HEMA-co-PEGMEA)) interpenetrating polymer networks (IPNs) functionalized with carboxylated spiropyran (SPCOOH) was designed and demonstrated as an on-demand DDS. The triggered-release mechanism relies on controlling the wetting behavior of the surface by light, exploiting different hydrophobicities between the "closed" and "open" isomers of spiropyran as a photoswitchable molecular gate on the surface of IPN (SP-photogated IPN). Light-triggered release of doxycycline (DOX) as a model drug indicated that the spiropyran (SP) molecules provide a hydrophobic layer around the drug carrier and have a good gate-closing efficiency for IPNs with 20-30% hydrogel content. Upon UV light irradiation, SP converts into an open hydrophilic merocyanine state, which triggers the release of DOX. These results were compared with a previously developed SP-bulk modified IPN using the same hydrogel as a control, proving the efficiency of the gated IPN system. The covalent attachment of SPCOOH to the alcohol groups of the hydrogel and the structural change caused by UV light was indicated with FTIR analysis. XPS results also confirm the presence of SP by indicating the atomic percentage of nitrogen with respect to the hydrogel content.

On-Demand Reversible UV-Triggered Interpenetrating Polymer Network-Based Drug Delivery System Using the Spiropyran-Merocyanine Hydrophobicity Switch

A reversible switchable on-demand UV-triggered drug delivery system (DDS) based on interpenetrating polymer networks (IPNs) with silicone as the host polymer and spiropyran (SP)-functionalized guest polymer is designed and demonstrated. The photo-responsive IPNs provide a new triggered drug delivery concept as they exploit the change in intermolecular interactions (work of adhesion) among the drug, matrix, and solvent when the incorporated hydrophobic SP moieties transform into the hydrophilic merocyanine form upon light irradiation without degradation and disruption of the DDS. The change in how the copolymer composition (hydrophilicity and content) and the lipophilicity of the drug (log P) affect the release profile was investigated. A thermodynamic model, based on Hansen solubility parameters, was developed to design and optimize the polymer composition of the IPNs to obtain the most efficient light-triggered drug release and suppression of the premature release. The developed IPNs showed excellent result for dopamine, l-dopa, and prednisone with around 90-95% light-triggered release. The model was applied to study the release behavior of drugs with different log P and to estimate if the light-induced hydrophobic-to-hydrophilic switch can overcome the work of adhesion between polymers and drugs and hence the desorption and release of the drugs. To the best of our knowledge, this is the first time that work of adhesion is used for this aim. Comparing the result obtained from the model and experiment shows that the model is useful for evaluating and estimating the release behavior of specific drugs merocyanine, IPN, DDS, and spiropyran.

Temperature and Photo Dual-Stimuli Responsive Block Copolymer Self-Assembly Micelles for Cellular Controlled Drug Release

To well adapt to the complicated physiological environments, it is necessary to engineer dual- and/or multi-stimuli responsive drug carriers for more effective drug release. For this, a novel temperature responsive lateral chain photosensitive block copolymer, poly[(N-isopropylacrylamide-co-N,N-dimethylacrylamide) -block-propyleneacylalkyl-4-azobenzoate] (P(NIPAM-co-DMAA)-b-PAzoHPA), is synthesized by atom transfer radical polymerization. The structure is characterized by ¹ H nuclear magnetic resonance spectrometry and laser light scattering gel chromatography system. The self-assembly behavior, morphology, and sizes of micelles are investigated by fluorescence spectroscopy, transmission electron microscope, and laser particle analyzer. Dual responsiveness to light and temperature is explored by ultraviolet-visible absorption spectroscopy. The results show that the copolymer micelles take on apparent light and temperature dual responsiveness, and its lower critical solution temperature (LCST) is above 37 °C, and changes with the trans-/cis- isomerization of azobenzene structure under UV irradiation. The blank copolymers are nontoxic, whereas the paclitaxel (PTX)-loaded counterparts possessed comparable anticancer activities to free PTX, with entrapment efficiency of 83.7%. The PTX release from the PTX-loaded micelles can be mediated by changing temperature and/or light stimuli. The developed block copolymers can potentially be used for cancer therapy as drug controlled release carriers.

Fabrication and in-vitro biocompatibility of freeze-dried CTS-nHA and CTS-nBG scaffolds for bone regeneration applications

The thought of biodegradable organic-inorganic composites composed of natural polymer chitosan and ceramic nanoparticles (hydroxyapatite and bioglass) can be considered as a solution for hard tissue engineering. In this paper, we described a comparative assessment of chitosan-nanohydroxyapatite (CTS-nHA) and chitosan-nano-bioglass (CTS-nBG) scaffolds. The dispersion of nanoscaled hydroxyapatite (nHA) and bioglass (nBG) in chitosan remained satisfactory. The freeze-dried composite based CTS-nHA and CTS-nBG scaffolds shown porous structure. The physiochemical and morphological analysis of all samples has been performed through X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The SEM image confirmed the presence of spherically shaped nHA particles of 4.20 μm and irregularly shaped nBG particles of 6.89 μm. The TEM analysis revealed the existence of 165.52 to 255.17 nm sized nHA particles and 167.35 to 334.69 nm sized nBG particles. TEM analysis also showed the interconnected structure of CTS-nHA and CTS-nBG nanocomposites. After seven days' incubation period, the CTS-nHA and CTS-nBG scaffolds shown good mineralization behavior in simulated body fluid (SBF). The CTS-nHA scaffolds exhibited enhanced compressive strength and elastic modulus compared with the CTS-nBG sample. The cell culture experiment revealed that fabricated scaffolds had good compatibility with fibroblast cells (L929, ATCC) and MG-63 which are able to adhere, proliferate, and migrate through the porous structure. All the obtained results clearly recommend that pre-loaded hydroxyapatite and bioglass nanoparticles can enhance the apatite formation. The scaffolds with chitosan, bioglass, and hydroxyapatite have better biomechanical characteristics and allow cell growth. Therefore, these scaffolds can be perfect candidates for various hard tissue engineering applications such as bone regeneration.

Mesoscale Simulations of pH-Responsive Amphiphilic Polymeric Micelles for Oral Drug Delivery

It is of great significance to study the structure property and self-assembly of amphiphilic block copolymer in order to effectively and efficiently design and prepare drug delivery systems. In this work, dissipative particle dynamics (DPD) simulation method was used to investigate the structure property and self-assembly ability of pH-responsive amphiphilic block copolymer poly(methyl methacrylate-co-methacrylic acid)-b-poly(aminoethyl methacrylate) (poly(MMA-co-MAA)-b-PAEMA). The effects of different block ratios (hydrophilic PAEMA segment and pH-sensitive PMAA segment) in copolymer on self-assembly and drug loading capacity including drug distribution were extensively investigated. The increase of hydrophilic PAEMA facilitated the formation of a typical core-shell structure as well as a hydrophobic PMAA segment. Furthermore, the optimal drug-carrier ratio was confirmed by an analysis of the drug distribution during the self-assembly process of block copolymer and model drug Ibuprofen (IBU). In addition, the drug distribution and nanostructure of IBU-loaded polymeric micelles (PMs) self-assembled from precise block copolymer (PMMA-b-PMAA-b-PAEMA) and block copolymer (poly(MMA-co-MAA)-b-PAEMA) with random pH-responsive/hydrophobic structure were evaluated, showing that almost all drug molecules were encapsulated into a core for a random copolymer compared to the analogue. The nanostructures of IBU-loaded PMs at different pH values were evaluated. The results displayed that the nanostructure was stable at pH < pK_a and anomalous at pH > pK_a which indicated drug release, suggesting that the PMs could be used in oral drug delivery. These findings proved that the amphiphilic block copolymer P(MMA₃₀-co-MAA₃₃)-b-PAEMA₃₈ with random structure and pH-sensitivity might be a potential drug carrier. Moreover, DPD simulation shows potential to study the structure property of PMs self-assembled from amphiphilic block copolymer.