Versatile Polymeric Microspheres with Tumor Microenvironment Bioreducible Degradation, pH-Activated Surface Charge Reversal, pH-Triggered “off–on” Fluorescence and Drug Release as Theranostic Nanoplatforms

A Novel NIR Fluorescence Probe with AIE Property to Image Viscosity in Nystatin-Induced Cell Model

As one of the most significant parameters in cellular microenvironment, viscosity levels could be used to determine the metabolic process of bioactive substances within cells. Abnormal viscosity levels are closely associated with a series of diseases. Therefore, the design and synthesis of fluorescent probes that can monitor changes of intracellular viscosity in real-time is of great significance for the study of disease development process. Here, a new viscosity-recognized NIR fluorescence probe W1 based on quinoline-malonitrile is synthesized, and it is not susceptible to interference substances. Besides, AIE probe W1 shows fast response, excellent photostability, low cytotoxicity, good linear relationship between fluorescence intensity value and viscosity. Based on the above advantages, probe W1 is used to image the change of viscosity level in the cell model induced by nystatin.

The Role of Microsphere Structures in Bottom-Up Bone Tissue Engineering

Bone defects have caused immense healthcare concerns and economic burdens throughout the world. Traditional autologous allogeneic bone grafts have many drawbacks, so the emergence of bone tissue engineering brings new hope. Bone tissue engineering is an interdisciplinary biomedical engineering method that involves scaffold materials, seed cells, and "growth factors". However, the traditional construction approach is not flexible and is unable to adapt to the specific shape of the defect, causing the cells inside the bone to be unable to receive adequate nourishment. Therefore, a simple but effective solution using the "bottom-up" method is proposed. Microspheres are structures with diameters ranging from 1 to 1000 µm that can be used as supports for cell growth, either in the form of a scaffold or in the form of a drug delivery system. Herein, we address a variety of strategies for the production of microspheres, the classification of raw materials, and drug loading, as well as analyze new strategies for the use of microspheres in bone tissue engineering. We also consider new perspectives and possible directions for future development.

pH-responsive intramolecular FRET-based self-tracking polymer prodrug nanoparticles for real-time tumor intracellular drug release monitoring and imaging

An intramolecular fluorescence resonance energy transfer (FRET)-based macromolecular theranostic prodrug was designed by directly conjugating Doxorubicin (DOX) as the FRET acceptor onto the naphthalimide side groups in the fluorescent copolymer PPEGMA₂₀-PNAP₈ as the FRET energy donor via an acid-labile imine bond, without a fluorogenic linker. The proposed PPEGMA₂₀-PNAP₈-DOX theranostic prodrug showed a high DOX content of 24.3% owing to a conjugation efficiency of > 93% under mild conjugation conditions. It could easily self-assemble into unique theranostic nanoparticles with a D_h of 71 nm. The theranostic nanoparticles showed excellent pH-triggered DOX release performance with very low premature drug leakage of 6.3% in normal physiological medium over 129 h, while>91% of the conjugated DOX was released in the acidic tumor intracellular microenvironment. MTT assays indicated the enhanced antitumor efficacy of the proposed theranostic nanoparticles compared with free DOX. Furthermore, because drug release was triggered by pH, orange fluorescence was restored to the blue fluorescence of the backbone copolymer. Such self-tracking pH-responsive colorful fluorescence variations during intracellular drug delivery and release are expected to allow real-time tumor intracellular drug release monitoring and imaging diagnosis.

Cell Type-Dependent Specificity and Anti-Inflammatory Effects of Charge-Reversible MSNs-COS-CMC for Targeted Drug Delivery in Cervical Carcinoma

The surface charge of nanocarriers inevitably affects drug delivery efficiency; however, the cancer cell specificity, anti-inflammatory effects, and charge-reversal points remain to be further addressed in biomedical applications. The aim of this study was to comprehensively assess the cancer cell specificity of DOX-loaded mesoporous silica-chitosan oligosaccharide-carboxymethyl chitosan nanoparticles (DOX@MSNs-COS-CMC) in MCF-7 and HeLa cells, inhibit the production of inflammatory cytokines, and improve the drug accumulation in the tumor site. Intracellular results reveal that the retention time prolonged to 48 h in both HeLa and MCF-7 cells at pH 7.4. However, DOX@MSNs-COS-CMC exhibited a cell type-dependent cytotoxicity and enhanced intracellular uptake in HeLa cells at pH 6.5, due to the clathrin-mediated endocytosis and macropinocytosis in HeLa cells in comparison with the vesicular transport in MCF-7 cells. Moreover, Pearson's correlation coefficient value significantly decreased to 0.25 after 8 h, prompting endosomal escape and drug delivery into the HeLa nucleus. After the treatment of MSNs-COS-CMC at 200 μg/mL, the inflammatory cytokines IL-6 and TNF-α level decreased by 70% and 80%, respectively. Tumor inhibition of DOX@MSNs-COS-CMC was 0.4 times higher than free DOX, alleviating cardiotoxicity and inflammation in the HeLa xenograft tumor model. Charge-reversible DOX@MSNs-COS-CMC could be a possible candidate for clinical therapy of cervical carcinoma.

Molecularly Imprinted Polymers (MIPs) as Theranostic Systems for Sunitinib Controlled Release and Self-Monitoring in Cancer Therapy

Cytotoxic agents that are used conventionally in cancer therapy present limitations that affect their efficacy and safety profile, leading to serious adverse effects. In the aim to overcome these drawbacks, different approaches have been investigated and, among them, theranostics is attracting interest. This new field of medicine combines diagnosis with targeted therapy; therefore, the aim of this study was the preparation and characterization of Molecularly Imprinted Polymers (MIPs) selective for the anticancer drug Sunitinib (SUT) for the development of a novel theranostic system that is able to integrate the drug controlled release ability of MIPs with Rhodamine 6G as a fluorescent marker. MIPs were synthesized by precipitation polymerization and then functionalized with Rhodamine 6G by radical grafting. The obtained polymeric particles were characterized in terms of particles size and distribution, ξ-potential and fluorescent, and hydrophilic properties. Moreover, adsorption isotherms and kinetics and in vitro release properties were also investigated. The obtained binding data confirmed the selective recognition properties of MIP, revealing that SUT adsorption better fitted the Langmuir model, while the adsorption process followed the pseudo-first order kinetic model. Finally, the in vitro release studies highlighted the SUT controlled release behavior of MIP, which was well fitted with the Ritger-Peppas kinetic model. Therefore, the synthesized fluorescent MIP represents a promising material for the development of a theranostic platform for Sunitinib controlled release and self-monitoring in cancer therapy.

A bottlebrush-architectured dextran polyprodrug as an acidity-responsive vector for enhanced chemotherapy efficiency

Compared to normal tissues, unique conditions in the tumor microenvironment, such as a lower pH, can induce accurate release of a drug into specific lesions. This strategy provides an efficient approach to overcome the issues of unexpected drug leakage and poor circulation stability, thereby reducing the side effects and enhancing the effect of cancer treatment. In this study, we designed a class of acid activatable supramolecular nano-prodrugs (DOM@DOX) with a bottlebrush architecture based on the dextran (DEX) polysaccharide, which connects with a hydrophilic polyethylene glycol chain by atom transfer radical polymerization and further conjugates with an anticancer drug doxorubicin (DOX) at the backbone of the copolymer via an acidity-responsive hydrazine bond. Furthermore, the DOM@DOX prodrug has a high drug loading up to 48 wt% for DOX, and the prodrug can maintain a stable nano-sized spherical shape in aqueous solution by a self-assembly strategy. In an acidic environment inside tumor cells, the hydrazine bond of the prodrug breaks, leading to the release of DOX from parental micelles. Owing to the small size of the carrier, the prodrug exhibits good intratumoral permeability, good circulation stability and significant tumor suppression efficiency in tumor-bearing mouse models, which is beneficial for the development of new generation nanomedicine for enhanced chemotherapy.

A γ-cyclodextrin-based metal-organic framework embedded with graphene quantum dots and modified with PEGMA via SI-ATRP for anticancer drug delivery and therapy

The γ-cyclodextrin-based metal-organic framework (γ-CD-MOF) composite was designed and prepared toward targeted anticancer drug delivery and cancer therapy. Large amounts of graphene quantum dots (GQDs) were embedded in the γ-CD-MOF matrix (denoted as GQDs@γ-CD-MOF) to endow the γ-CD-MOF with strong fluorescence, which was then modified by pH responsive poly(ethyleneglycol)dimethacrylate (PEGMA) through surface initiated atom transfer radical polymerization (SI-ATRP) to fabricate the PEGMA@GQDs@γ-CD-MOF composite. Then, the cancer cell-targeted probe was obtained by immobilizing the AS1411 aptamer over it (denoted as AS1411@PEGMA@GQDs@γ-CD-MOF) and it exhibits pH-responsive release function and excellent targeting ability. Large amounts of antitumour drug, doxorubicin hydrochloride (DOX), could be encapsulated within this composite due to the chemical-rich functionality, and the resultant pH-responsive DOX delivery system (denoted as DOX/AS1411@PEGMA@GQDs@γ-CD-MOF) displayed a higher DOX loading of 89.1% with sustained release than the pristine γ-CD-MOF and GQDs@γ-CD-MOF. The targeting specificity investigation revealed that this DOX delivery system was effectively internalized via receptor mediated endocytosis with high selectivity. The in vivo antitumour study with tumour-bearing mice illustrated that the tumour growth can be effectively suppressed and partially ablated with negligible side effects after treatments. Therefore, the proposed AS1411@PEGMA@GQD@γ-CD-MOF composite is promising for effective DOX delivery and tumour growth inhibition both in vitro and in vivo, showing great potential for anticancer therapy.