The tumor accumulation and therapeutic efficacy of doxorubicin carried in calcium phosphate-reinforced polymer nanoparticles

Nature-inspired protein mineralization strategies for nanoparticle construction: advancing effective cancer therapy

Recently, nanotechnology has shown great potential in the field of cancer therapy due to its ability to improve the stability and solubility and reduce side effects of drugs. The biomimetic mineralization strategy based on natural proteins and metal ions provides an innovative approach for the synthesis of nanoparticles. This strategy utilizes the unique properties of natural proteins and the mineralization ability of metal ions to combine nanoparticles through biomimetic mineralization processes, achieving the effective treatment of tumors. The precise control of the mineralization process between proteins and metal ions makes it possible to obtain nanoparticles with the ideal size, shape, and surface characteristics, thereby enhancing their stability and targeting ability in vivo. Herein, initially, we analyze the role of protein molecules in biomineralization and comprehensively review the functions, properties, and applications of various common proteins and metal particles. Subsequently, we systematically review and summarize the application directions of nanoparticles synthesized based on protein biomineralization in tumor treatment. Specifically, we discuss their use as efficient drug delivery carriers and role in mediating monotherapy and synergistic therapy using multiple modes. Also, we specifically review the application of nanomedicine constructed through biomimetic mineralization strategies using natural proteins and metal ions in improving the efficiency of tumor immunotherapy.

Combining Olaparib and Ascorbic Acid on Nanoparticles to Enhance the Drug Toxic Effects in Pancreatic Cancer

Introduction

Pancreatic cancer (PC) shows a very poor response to current treatments. Development of drug resistance is one of the causes of the therapy failure, being PARP1 (poly ADP-ribose polymerase 1) a relevant protein in the resistance mechanism. In this work, we have functionalized calcium phosphate-based nanoparticles (NPs) with Olaparib (OLA, a PARP-1 inhibitor) in combination with ascorbic acid (AA), a pro-oxidative agent, to enhance their individual effects.

Methods

Amorphous Calcium Phosphate (ACP) NPs were synthesized through a biomimetic approach and then functionalized with OLA and AA (NP-ACP-OLA-AA). After evaluation of the loading capacity and release kinetic, cytotoxicity, cell migration, immunofluorescence, and gene expression assays were performed using pancreatic tumor cell lines. In vivo studies were carried out on tumors derived from the PANC-1 line in NOD SCID gamma (NSG) mice.

Results

NP-ACP-OLA-AA was loaded with 13%wt of OLA (75% loading efficiency) and 1% of AA, respectively. The resulting dual nanosystem exhibited a gradual release of OLA and AA, being the latter protected from degradation in solution. This ensured the simultaneous availability of OLA and AA for a longer period, at least, during the entire time of in vitro cell experiments (72 hours). In vitro studies indicated that NP-ACP-OLA-AA showed the best cytotoxic effect outperforming that of the free OLA and a higher genotoxicity and apoptosis-mediated cytotoxic effect in human pancreatic ductal adenocarcinoma cell line. Interestingly, the in vivo assays using immunosuppressed mice with PANC-1-induced tumors revealed that NP-ACP-OLA-AA produced a higher tumor volume reduction (59.1%) compared to free OLA (28.3%) and increased the mice survival.

Conclusion

Calcium phosphate NPs, a highly biocompatible and biodegradable system, were an ideal vector for the OLA and AA co-treatment in PC, inducing significant therapeutic benefits relative to free OLA, including cytotoxicity, induction of apoptosis, inhibition of cell migration, tumor growth, and survival.

Novel Bioengineering Strategies to Improve Bioavailability and In Vivo Circulation of H-Ferritin Nanocages by Surface Functionalization

Due to its unique architecture and innate capability to specifically target cancer cells, ferritin has emerged as an attractive class of biomaterials for drug delivery. In many studies, various chemotherapeutics have been loaded into ferritin nanocages constituted by H-chains of ferritin (HFn), and their related anti-tumor efficacy has been explored by employing different strategies. Despite the multiple advantages and the versatility of HFn-based nanocages, there are still many challenges to face for their reliable implementation as drug nanocarriers in the process of clinical translation. This review aims at providing an overview of the significant efforts expended during recent years to maximize the features of HFn in terms of increased stability and in vivo circulation. The most considerable modification strategies explored to improve bioavailability and pharmacokinetics profiles of HFn-based nanosystems will be discussed herein.

Colon cancer therapy with calcium phosphate nanoparticles loading bioactive compounds from Euphorbia lathyris: In vitro and in vivo assay

Amorphous calcium phosphate nanoparticles (ACP NPs) exhibit excellent biocompatibility and biodegradability properties. ACP NPs were functionalized with two coumarin compounds (esculetin and euphorbetin) extracted from Euphorbia lathyris seeds (BC-ACP NPs) showing high loading capacity (0.03% and 0.34% (w/w) for esculetin and euphorbetin, respectively) and adsorption efficiency (2.6% and 33.5%, respectively). BC-ACP NPs, no toxic to human blood cells, showed a more selective cytotoxicity against colorectal cancer (CRC) cells (T-84 cells) (IC50, 71.42 µg/ml) compared to non-tumor (CCD18) cells (IC50, 420.77 µg/ml). Both, the inhibition of carbonic anhydrase and autophagic cell death appeared to be involved in their action mechanism. Interestingly, in vivo treatment with BC-ACPs NPs using two different models of CRC induction showed a significant reduction in tumor volume (62%) and a significant decrease in the number and size of polyps. A poor development of tumor vasculature and invasion of normal tissue were also observed. Moreover, treatment increased the bacterial population of Akkermansia by restoring antioxidant systems in the colonic mucosa of mice. These results show a promising pathway to design innovative and more efficient therapies against CRC based on biomimetic calcium phosphate NPs loaded with natural products.

A Polyplex in a Shell: The Effect of Poly(aspartic acid)-Mediated Calcium Carbonate Mineralization on Polyplexes Properties and Transfection Efficiency

Mineralization by exposure of organic templates to supersaturated solutions is used by many living organisms to generate specialized materials to perform structural or protective functions. Similarly, it was suggested that improved robustness acquired through mineralization under natural conditions could be an important factor for virus survival outside of a host for better transfection of cells. Here, inspired by this fact, we developed a nonviral tricomponent polyplex system for gene delivery capable of undergoing mineralization. First, we fabricated anionic polyplexes carrying pDNA by self-assembly with a lipid-modified cationic polymer and coating by poly(aspartic acid). Then, we submitted the polyplexes to a two-step mineralization reaction to precipitate CaCO₃ under various supersaturations. We carried out detailed morphological studies of the mineralized polyplexes and identified which parameters of the fabrication process were influential on transfection efficiency. We found that mineralization with CaCO₃ is efficient in promoting transfection efficiency as long as a certain Ca²⁺/CO₃^2- lower limit ratio is respected. However, calcium incubation can also be used to achieve similar effects at higher concentrations depending on polyplex composition, probably due to the formation of physical cross-links by calcium binding to poly(aspartic acid). We proposed that the improved robustness and transfection efficiency provided by means of mineralization can be used to expand the possible applications of polyplexes in gene therapy.

Mineralized vectors for gene therapy

There is an intense interest in developing materials for safe and effective delivery of polynucleotides using non-viral vectors. Mineralization of organic templates has long been used to produce complex materials with outstanding biocompatibility. However, a lack of control over mineral growth has limited the applicability of mineralized materials to a few in vitro applications. With better control over mineral growth and surface functionalization, mineralized vectors have advanced significantly in recent years. Here, we review the recent progress in chemical synthesis, physicochemical properties, and applications of mineralized materials in gene therapy, focusing on structure-function relationships. We contrast the classical understanding of the mineralization mechanism with recent ideas of mineralization. A brief introduction to gene delivery is summarized, followed by a detailed survey of current mineralized vectors. The vectors derived from calcium phosphate are articulated and compared to other minerals with unique features. Advanced mineral vectors derived from templated mineralization and specialty coatings are critically analyzed. Mineral systems beyond the co-precipitation are explored as more complex multicomponent systems. Finally, we conclude with a perspective on the future of mineralized vectors by carefully demarcating the boundaries of our knowledge and highlighting ambiguous areas in mineralized vectors. STATEMENT OF SIGNIFICANCE: Therapy by gene-based medicines is increasingly utilized to cure diseases that are not alleviated by conventional drug therapy. Gene medicines, however, rely on macromolecular nucleic acids that are too large and too hydrophilic for cellular uptake. Without tailored materials, they are not functional for therapy. One emerging class of nucleic acid delivery system is mineral-based materials. The fact that they can undergo controlled dissolution with minimal footprint in biological systems are making them attractive for clinical use, where safety is utmost importance. In this submission, we will review the emerging synthesis technology and the range of new generation minerals for use in gene medicines.

Synergistic Effect of Toceranib and Nanohydroxyapatite as a Drug Delivery Platform-Physicochemical Properties and In Vitro Studies on Mastocytoma Cells

A new combination of Toceranib (Toc; 5-[(5Z)-(5-Fluoro-2-oxo-1,2-dihydro-3H-indol-3-ylidene)methyl]-2,4-dimethyl-N-[2-(pyrrolidin-1-yl)ethyl]-1H-pyrrole-3-carboxamide) with nanohydroxyapatite (nHAp) was proposed as an antineoplastic drug delivery system. Its physicochemical properties were determined as crystallinity, grain size, morphology, zeta potential and hydrodynamic diameter as well as Toceranib release. The crystalline nanorods of nHAp were synthesised by the co-precipitation method, while the amorphous Toceranib was obtained by its conversion from the crystalline form during nHAp–Toc preparation. The surface interaction between both compounds was confirmed using Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV–Vis) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). The nHAp–Toc showed a slower and prolonged release of Toceranib. The release behaviour was affected by hydrodynamic size, surface interaction and the medium used (pH). The effectiveness of the proposed platform was tested by comparing the cytotoxicity of the drug combined with nHAp against the drug itself. The compounds were tested on NI-1 mastocytoma cells using the Alamar blue colorimetric technique. The obtained results suggest that the proposed platform shows high efficiency (the calculated IC50 is 4.29 nM), while maintaining the specificity of the drug alone. Performed analyses confirmed that nanohydroxyapatite is a prospective drug carrier and, when Toceranib-loaded, may be an idea worth developing with further research into therapeutic application in the treatment of canine mast cell tumour.

A polymer‑calcium phosphate nanocapsule for RNAi-induced oxidative stress and cascaded chemotherapy

As most of intracellular reactive oxygen species (ROS) is produced in the mitochondria, mitochondrial modulation of cancer cell is a promising strategy for maximizing the in situ-activable combination therapy of oxidative catastrophe and cascaded chemotherapy. Herein, a serum-stable polymer‑calcium phosphate (CaP) hybrid nanocapsule carrying siRNA against ADP-ribosylation factor 6 (Arf6) overexpressed in cancer cells and parent drug camptothecin (CPT), designated as PTkCPT/siRNA, was developed for the RNAi-induced oxidative catastrophe and cascaded chemotherapy. A copolymer of mPEG-P(Asp-co-TkCPT), covalently tethered with chemotherapeutic CPT via a ROS-labile dithioketal (Tk) linker, was synthesized and self-assembled into a PTkCPT micelle as a nanotemplate for the CaP mineralization. The as-prepared PTkCPT/siRNA nanoparticle showed a core-shell-distinct nanocapsule which was consisted of a spherical polymeric core enclosed within a CaP shell capable of releasing siRNA in response to lysosomal acidity. Blocking Arf6 signal pathway of cancer cells led to their mitochondrial aggregation and subsequently induced a burst of ROS for oxidative catastrophe, which further triggered the cascaded CPT chemotherapy via the breakage of ROS-labile dithioketal linker. This strategy of RNAi-induced oxidative catastrophe and cascaded chemotherapy resulted in a significant combination effect on cancer cell killing and tumor growth inhibition in mice with low side effects, and provided a promising paradigm for precise cancer therapy.

Mineralized polyplexes for gene delivery: Improvement of transfection efficiency as a consequence of calcium incubation and not mineralization

Gene therapy is an emerging field in which nucleic acids are used to control protein expression. The necessity of delivering nucleic acids to specific cell types and intracellular sites demands the use of highly specialized gene carriers. As a carrier modification technique, mineralization has been successfully used to modify viral and non-viral carriers, providing new properties that ultimately aim to increase the transfection efficiency. However, for the specific case of polyplexes used in gene therapy, recent literature shows that interaction with calcium, a fundamental step of mineralization, might be effective to increase transfection efficiency, leaving an ambiguity about of the role of mineralization for this type of gene carriers. To answer this question and to reveal the properties responsible for increasing transfection efficiency, we mineralized poly(aspartic acid) coated polyplexes at various CaCl₂ and Na₃PO₄ concentrations, and evaluated the resultant carriers for physicochemical and morphological characteristics, as well as transfection and delivery efficiency with MC3T3-E1 mouse osteoblastic cells. We found that both mineralization and calcium incubation positively affected the transfection efficiency and uptake of polyplexes in MC3T3-E1 cells. However, this effect originated from the properties achieved by polyplexes after the calcium incubation step that are maintained after mineralization, including particle size increase, improved pDNA binding, and adjustment of zeta potential. Considering that mineralization can be a longer process than calcium incubation, we find that calcium incubation might be sufficient and preferred if improved transfection efficiency in vitro is the only effect desired.

Calcium phosphate-polymeric nanoparticle system for co-delivery of microRNA-21 inhibitor and doxorubicin

Targeted combination therapy has shown promise to achieve maximum therapeutic efficacy by overcoming drug resistance. MicroRNA-21 (miR-21) is frequently overexpressed in various cancer types including breast and non-small cell lung cancer and its functions can be inhibited by miR inhibitor (miR-21i). A combination of miR-21i and a chemo drug, doxorubicin (Dox), can provide synergistic effects. Here, we developed a calcium phosphate (CaP)-coated nanoparticle (NP) formulation to co-deliver miR-21i along with Dox. This NP design can be used to deliver the two agents with different physiochemical properties. The NP formulation was optimized for particle size, polydispersity, Dox loading, and miR-21i loading. The NP formulation was confirmed to downregulate miR-21 levels and upregulate tumor suppressor gene levels. The cytotoxic efficacy of the combined miR-21i and Dox-containing NPs was found to be higher than that of Dox. Therefore, the CaP-coated hybrid lipid-polymeric NPs hold potential for the delivery of miR-21i and Dox.

Colloidally Stabilized DSPE-PEG-Glucose/Calcium Phosphate Hybrid Nanocomposites for Enhanced Photodynamic Cancer Therapy via Complementary Mitochondrial Ca2+ Overload and Autophagy Inhibition

Autophagy inhibition could hinder the underlying protective mechanisms in the course of tumor treatment. The advances in autophagy inhibition have driven focus on the functionalized nanoplatforms by combining the current treatment paradigms with complementary autophagy inhibition for enhanced efficacy. Furthermore, Ca2+ overload is also a promising adjuvant target for the tumor treatment by augmenting mitochondrial damage. In this view, complementary mitochondrial Ca2+ overload and autophagy inhibition were first demonstrated as a novel strategy suitable for homing in on the shortage of photodynamic therapy (PDT). We constructed biodegradable tumor-targeted inorganic/organic hybrid nanocomposites (DPGC/OI) synchronously encapsulating IR780 and Obatoclax by biomineralization of the nanofilm method, which consists of pH-triggered calcium phosphate (CP), long circulation phospholipid block copolymers 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)-poly(ethylene glycol) (PEG)2000-glucose (DPG). In the presence of the hydrophilic PEG chain and glucose transporter 1 (Glut-1) ligands, DPGC would become an effectively tumor-oriented nanoplatform. Subsequently, IR780 as an outstanding photosensitizer could produce increased amounts of toxic reactive oxygen species (ROS) after laser irradiation. Calcium phosphate (CP) as the Ca2+ nanogenerator could generate Ca2+ at low pH to induce mitochondrial Ca2+ overload. The dysfunction of mitochondria could enhance increased amounts of ROS. Based on the premise that autophagy would degrade dysfunctional organelles to sustain metabolism and homeostasis, which might participate in resistance to PDT, Obatoclax as an autophagy inhibitor would hinder the protective mechanism from cancer cells with negligible toxicity. Such an enhanced PDT via mitochondrial Ca2+ overload and autophagy inhibition could be realized by DPGC/OI.

Icebreaker-inspired Janus nanomotors to combat barriers in the delivery of chemotherapeutic agents

Cancer chemotherapy remains challenging to pass through various biological and pathological barriers such as blood circulation, tumor infiltration and cellular uptake before the intracellular release of antineoplastic agents. Herein, icebreaker-inspired Janus nanomotors (JMs) are developed to address these transportation barriers. Janus nanorods (JRs) are constructed via seed-defined growth of mesoporous silica nanoparticles on doxorubicin (DOX)-loaded hydroxyapatite (HAp) nanorods. One side of JRs is grafted with urease as the motion power via catalysis of physiologically existed urea, and hyaluronidase (HAase) is on the other side to digest the viscous extracellular matrices (ECM) of tumor tissues. The rod-like feature of JMs prolongs the blood circulation, and the self-propelling force and instantaneous digestion of hyaluronic acid along the moving paths promote extravasation across blood vessels and penetration in tumor mass, leading to 2-fold higher drug levels in tumors after JM administration than those with JRs. The digestion of ECM in the diffusion paths is more effective to enhance drug retention and diffusion in tumors compared with enzyme-mediated motion. The ECM digestion and motion capabilities of JMs show no influence on the endocytosis mechanism, but lead to over 3-fold higher cellular uptake than those of pristine JRs. The JM treatment promotes therapeutic efficacy in terms of survival prolongation, tumor growth inhibition and cell apoptosis induction and causes no tumor metastasis to lungs with normal alveolar spaces. Thus, the self-driven motion and instantaneous clearance of diffusion routes demonstrate a feasible strategy to combat a series of biological barriers in the delivery of chemotherapeutic agents in favor of antitumor efficacy.

Dual stimuli-responsive polypeptide-calcium phosphate hybrid nanoparticles for co-delivery of multiple drugs in cancer therapy

In this study, a new type of polypeptide, crosslinked methoxy poly(ethylene glycol)-g-poly(aspartic acid)-g-tyrosine (CPPT), was synthesized via a green and simple one-pot polymerization method. With the disulfide-crosslinked interlayer and the CaP shell, the pH and redox dual-sensitive polypeptide-based organic-inorganic hybrid nanoparticles encapsulated curcumin (Cur) into the hydrophobic core of micelles and loaded doxorubicin hydrochloride (DOX) on the hydrophilic segment of micelles as well as CaP shell. The spherical Cur- and DOX-loaded nanoparticles (CPPT@CaP-CD) showed a hydrodynamics size of about 157.9 ± 3.9 nm. The premature leakage of drugs from the nanoparticles at physiological pH was efficiently restrained because of the enhanced structure integrity, whereas at acidic and hypoxia microenvironment the release of both drugs was promoted due to the rapid dissolution of the CaP shell and the break of the disulfide crosslinked network, facilitating the stimuli-responsive controllable drugs release. In vitro anticancer activity evaluation revealed that the co-loaded nanoparticles presented higher cytotoxicity against A549 cells compared with that of the free combination of Cur + DOX. Confocal laser scanning microscopy observation indicated that more DOX and Cur were released into the nucleus triggered by the up-regulated intracellular glutathione (GSH) concentration and decreased pH, displaying enhanced cell uptake. The self-assembling polypeptide-based dual-sensitive drug co-delivery system could be a promising platform for efficient chemotherapy.

Biomineralization-inspired dasatinib nanodrug with sequential infiltration for effective solid tumor treatment

The complex blood environment, heterogenic enhanced permeability and retention (EPR) effect, and dense matrix comprise the primary "leakage obstacles" impeding specific accumulation and penetration of nanodrugs against solid tumors, thus forming a key bottleneck for their clinical application. Herein, we present a biomineralization-inspired dasatinib (DAS) nanodrug (CIPHD/DAS) that sequentially permeates all of the abovementioned hindrances for efficient treatment of solid tumors. CIPHD/DAS exhibited a robust hybrid structure constructed from an iRGD-modified hyaluronic acid-deoxycholic acid organic core and a calcium phosphate mineral shell. In vitro and in vivo data demonstrated the mechanism of sequential tumoral infiltration was based on mineral-stiffened blood circulation with decreased premature drug leakage, iRGD-endowed tumor-specific transendothelial transport for "first-order promotion of accumulation" and DAS-mediated restoration of fibrotic stromal homeostasis for "second-order promotion of penetration". Resultantly, CIPHD/DAS showed remarkable distal drug availability in desmoplastic 4T1/CAFs orthotropic mouse models and significantly suppressed tumor growth and metastasis. This optimized strategy with sequential permeabilization of the capital "leakage obstacles" validates a promising paradigm to conquer the "impaired delivery and penetration" associated bottleneck of nanodrugs in the clinical treatment of solid tumors.

Calcium phosphate nanoneedle based gene delivery system for cancer genetic immunotherapy

Ovarian cancer has become one of the most common gynecological cancers with a high mortality. However, conventional surgery together with combination chemotherapy is difficult to achieve ideal therapeutic effect. Although genetic immunotherapy is applied to active immune responses against cancer, the absence of efficient in vivo gene delivery technique is still an obstacle in clinical application. To overcome these problems, a minicircle DNA vector encoding humanized anti-EpCAM/CD3 bispecific antibody (BsAb_EPH) has been constructed. Moreover, different shapes of calcium phosphate (CaPO) biomaterials were prepared. Specifically, the CaPO-nanoneedle-mediated "cell perforation" transfection technology achieves high levels of gene expression in peritoneal cavity. In an intraperitoneal xenograft model with human ovarian cancer cell line SKOV3, the CaPO-nanoneedle/minicircle DNA system expressed BsAb_EPH resulted in significant retardation of cancer growth and extension of mouse life-span with limited toxicity. And this system can be made as off-the-shelf and easy-to-use products. Therefore, CaPO-nanoneedle based non-viral gene delivery technology will have great potential in clinical application.

Theranostic nanocarriers combining high drug loading and magnetic particle imaging

We report preparation of theranostic nanocarriers loaded with up to 50 wt% of the anticancer drug doxorubicin that contain magnetic nanoparticles which enable Magnetic Particle Imaging (MPI), an emerging technology for quantitative and unambiguous imaging of the nanocarriers. The nanocarriers, coated with poly(ethylene glycol)-block-poly(lactic acid) (PEG_4.9kD-b-PLA_6kD) block copolymer for colloidal stability, are composed of a hydrophobic core of precipitated hydrolysable doxorubicin prodrug (proDox) and magnetic nanoparticles. Transmission electron microscopy (TEM) shows evidence of precipitated proDox for nanocarriers with high drug loading of up to 50 wt%. MPI measurements show that the nanocarriers can be quantitatively imaged. The nanocarriers are internalized by MDA-MB-231 cells and their IC₅₀ value via metabolic assay is 1.1 µM, compared to 0.21 µM for free doxorubicin. The release rate from the nanocarriers was dependent on environmental pH. These nanocarriers with high drug loading and quantitative imaging are promising candidates for future applications.

Calcium phosphate nanocarriers for drug delivery to tumors: imaging, therapy and theranostics

Calcium phosphate (CaP) was engineered as a drug delivery nanocarrier nearly 50 years ago due to its biocompatibility and biodegradability. In recent years, several approaches have been developed for the preparation of size-controllable, stable and multifunctional CaP nanocarriers, and several targeting moieties have also been decorated on the surface of these nanocarriers for active targeting. The CaP nanocarriers have been utilized for loading probes, nucleic acids, anticancer drugs and photosensitizers for cancer imaging, therapy and theranostics. Herein, we reviewed the recent advances in the preparation strategies of CaP nanocarriers and the applications of these nanocarriers in tumor diagnosis, gene delivery, drug delivery and theranostics and finally provided perspectives.

Biomolecule-assisted green synthesis of nanostructured calcium phosphates and their biomedical applications

Calcium phosphates (CaPs) are ubiquitous in nature and vertebrate bones and teeth, and have high biocompatibility and promising applications in various biomedical fields. Nanostructured calcium phosphates (NCaPs) are recognized as promising nanocarriers for drug/gene/protein delivery owing to their high specific surface area, pH-responsive degradability, high drug/gene/protein loading capacity and sustained release performance. In order to control the structure and surface properties of NCaPs, various biomolecules with high biocompatibility such as nucleic acids, proteins, peptides, liposomes and phosphorus-containing biomolecules are used in the synthesis of NCaPs. Moreover, biomolecules play important roles in the synthesis processes, resulting in the formation of various NCaPs with different sizes and morphologies. At room temperature, biomolecules can play the following roles: (1) acting as a biocompatible organic phase to form biomolecule/CaP hybrid nanostructured materials; (2) serving as a biotemplate for the biomimetic mineralization of NCaPs; (3) acting as a biocompatible modifier to coat the surface of NCaPs, preventing their aggregation and increasing their colloidal stability. Under heating conditions, biomolecules can (1) control the crystallization process of NCaPs by forming biomolecule/CaP nanocomposites before heating; (2) prevent the rapid and disordered growth of NCaPs by chelating with Ca2+ ions to form precursors; (3) provide the phosphorus source for the controlled synthesis of NCaPs by using phosphorus-containing biomolecules. This review focuses on the important roles of biomolecules in the synthesis of NCaPs, which are expected to guide the design and controlled synthesis of NCaPs. Moreover, we will also summarize the biomedical applications of NCaPs in nanomedicine and tissue engineering, and discuss their current research trends and future prospects.

CaP coated mesoporous polydopamine nanoparticles with responsive membrane permeation ability for combined photothermal and siRNA therapy

Combined photothermal and gene therapy provides a promising modality toward cancer treatment, yet facile integration and controlled codelivery of gene payloads and photothermal conversion agents (PTCAs) remains a great challenge. Inspired by the robust wet adhesion of marine mussels, we present a rationally designed nanosystem constructed by using hybrid mesoporous polydopamine nanoparticles (MPDA) with sub-100 nm sizes and a high photothermal conversion efficiency of 37%. The surface of the particles were modified with tertiary amines by the facile Michael addition/Schiff base reactions of PDA to realize high siRNA loading capacity (10 wt%). Moreover, a successful calcium phosphate (CaP) coating via biomineralization was constructed on the cationic nanoparticle to prohibit premature release of siRNA. The CaP coating underwent biodegradation in weakly-acidic subcellular conditions (lysosomes). The synergistic integration of tertiary amines and catechol moieties on the subsequently exposed surfaces was demonstrated to feature the destabilization/disruption ability toward model cellular membranes via the greatly enhanced interfacial adhesion and interactions. Consequently, sufficient permeability of lysosomal membranes, and in turn, a high lysosomal escape efficiency, was realized, which then resulted in high gene silencing efficiencies via sufficient cytosolic delivery of siRNA. When an efficient knocking down (65%) of survivin (an inhibitor of apoptosis proteins) was combined with a subsequent photothermal ablation, remarkably higher therapeutic efficiencies were observed both in vitro and in vivo, as compared with monotherapy. The system may help to pave a new avenue on the utilization of bio-adhesive surfaces for handling the obstacles of combined photothermal and gene therapy. STATEMENT OF SIGNIFICANCE: Polydopamine (PDA) based porous photothermal-conversion agent (PTCA) with sufficiently high conversion efficiency was employed to deliver photothermal/gene therapy modalities towards cancer treatment. CaP coating via PDA-induced biomineralization was constructed to prohibit premature release of siRNA loaded in the pore space of the nanocarriers. Responsive degradation of CaP also led to the exposure of membrane-lytic surfaces built through the synergistic integration of tertiary amines and catechol moieties, and in turn the significantly enhanced lysosomal escape and cytosol siRNA delivery. Therapeutic targeting of survivin was successfully applied for activation of apoptosis and programmed cell death. Combined photothermal and gene therapy improved therapeutic effectiveness.

Folate-modified hydroxyapatite nanorods induce apoptosis in MCF-7 cells through a mitochondrial-dependent pathway

The targeted delivery of therapeutic drugs into cancer cells is a facile method to improve therapeutic efficacy.

Engineering folate-targeting diselenide-containing triblock copolymer as a redox-responsive shell-sheddable micelle for antitumor therapy in vivo

The oxidation-reduction (redox)-responsive micelle system is based on a diselenide-containing triblock copolymer, poly(ε-caprolactone)-bis(diselenide-methoxy poly(ethylene glycol)/poly(ethylene glycol)-folate) [PCL-(SeSe-mPEG/PEG-FA)₂]. This has helped in the development of tumor-targeted delivery for hydrophobic anticancer drugs. The diselenide bond, as a redox-sensitive linkage, was designed in such a manner that it is located at the hydrophilic-hydrophobic hinge to allow complete collapse of the micelle and thus efficient drug release in redox environments. The amphiphilic block copolymers self-assembled into micelles at concentrations higher than the critical micelle concentration (CMC) in an aqueous environment. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses showed that the micelles were spherical with an average diameter of 120 nm. The insoluble anticancer drug paclitaxel (PTX) was loaded into micelles, and its triggered release behavior under different redox conditions was verified. Folate-targeting micelles showed an enhanced uptake in 4T1 breast cancer cells and in vitro cytotoxicity by flow cytometry and (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) assay, respectively. Delayed tumor growth was confirmed in the subcutaneously implanted 4T1 breast cancer in mice after intraperitoneal injection. The proposed redox-responsive copolymer offers a new type of biomaterial for drug delivery into cancer cells in vivo.

STATEMENT OF SIGNIFICANCE

On-demand drug actuation is highly desired. Redox-responsive polymeric DDSs have been shown to be able to respond and release their cargo in a selective manner when encountering a significant change in the potential difference, such as that present between cancerous and healthy tissues. This study offers an added advantage to the field of redox-responsive polymers by reporting a new type of shell-sheddable micelle based on an amphiphilic triblock co-polymer, containing diselenide as a redox-sensitive linkage. The linkage was smartly located at the hydrophilic-hydrophilic bridge in the co-polymer offering complete collapse of the micelle when exposed to the right trigger. The system was able to delay tumor growth and reduce toxicity in a breast cancer tumor model following intraperitoneal injection in mice.

Biomineralized hybrid nanoparticles for imaging and therapy of cancers

In this review, we describe the research trends of hybrid nanocarriers developed based on a biomimetic mineralization process, and their recent applications in imaging and therapy of cancers. Organic-inorganic hybrid nanostructures formed by diverse biomimetic mineralization approaches are briefly reviewed, and particularly, the biomedical applications of these hybrid nanocarriers for the diagnosis and therapy of cancers are discussed. Biomineralization is an important process in which living organisms produce biominerals, such as calcium phosphate (CaP), calcium carbonate (CaCO3), and silica (SiO2), to strengthen their tissues, as found in the formation of bone and teeth. Introducing the artificial biomimetic mineralization process to nanobiotechnology has inspired researchers to develop smart stimuli-responsive nanoparticles for multiple purposes, such as improved therapeutic activity and activatable imaging of cancers.

Highly Augmented Drug Loading and Stability of Micellar Nanocomplexes Composed of Doxorubicin and Poly(ethylene glycol)-Green Tea Catechin Conjugate for Cancer Therapy

Low drug loading and instability in blood circulation are two key challenges that impede the successful clinical translation of nanomedicine, as they result in only marginal therapeutic efficacy and toxic side effects associated with premature drug leakage, respectively. Herein, highly stable and ultrahigh drug loading micellar nanocomplexes (MNCs) based on the self-assembly of the anticancer drug doxorubicin (DOX) and a poly(ethylene glycol)-epigallocatechin-3-O-gallate (EGCG) conjugate are developed. The formation of these MNCs is facilitated by strong favorable intermolecular interactions between the structurally similar aromatic EGCG and DOX molecules, which impart exceptionally high drug-loading capability of up to 88% and excellent thermodynamic and kinetic stability. Unlike two clinical formulations of DOX-free DOX and liposomal DOX, which are not effective below their lethal dosages, these DOX-loaded MNCs demonstrate significant tumor growth inhibition in vivo on a human liver cancer xenograft mouse model with minimal unwanted toxicity. Overall, these MNCs can represent a safe and effective strategy to deliver DOX for cancer therapy.

Biodegradable Drug-Loaded Hydroxyapatite Nanotherapeutic Agent for Targeted Drug Release in Tumors

Tumor-targeted drug delivery systems have been increasingly used to improve the therapeutic efficiency of anticancer drugs and reduce their toxic side effects in vivo. Focused on this point, doxorubicin (DOX)-loaded hydroxyapatite (HAP) nanorods consisting of folic acid (FA) modification (DOX@HAP-FA) were developed for efficient antitumor treatment. The DOX-loaded nanorods were synthesized through in situ coprecipitation and hydrothermal method with a DOX template, demonstrating a new procedure for drug loading in HAP materials. DOX could be efficiently released from DOX@HAP-FA within 24 h in weakly acidic buffer solution (pH = 6.0) because of the degradation of HAP nanorods. With endocytosis under the mediation of folate receptors, the nanorods exhibited enhanced cellular uptake and further degraded, and consequently, the proliferation of targeted cells was inhibited. More importantly, in a tumor-bearing mouse model, DOX@HAP-FA treatment demonstrated excellent tumor growth inhibition. In addition, no apparent side effects were observed during the treatment. These results suggested that DOX@HAP-FA may be a promising nanotherapeutic agent for effective cancer treatment in vivo.

Primary tumor and pre-metastatic niches co-targeting “peptides-lego” hybrid hydroxyapatite nanoparticles for metastatic breast cancer treatment

Hybrid hydroxyapatite nanoparticles orchestrating tumor metastasis resisting therapy (TMRT) and tumor metastasis targeting therapy (TMTT).

Calcium-based biomaterials for diagnosis, treatment, and theranostics

Calcium-based biomaterials with good biosafety and bio-absorbability are promising for biomedical applications such as diagnosis, treatment, and theranostics.

A pH-responsive polymer based on dynamic imine bonds as a drug delivery material with pseudo target release behavior

In this study, pentaerythritol tetra(3-mercaptopropionate)-allylurea-poly(ethylene glycol) (PETMP-AU-PEG), produced by the Schiff-base reaction between terminal-aldehyded PEG and PETMP-AU, was used to prepare doxorubicin (DOX)-loaded polymers for triggered release.

Bridging the divide: preclinical research discrepancies between triple-negative breast cancer cell lines and patient tumors

Triple-negative breast cancer (TNBC) is the most refractory subtype of breast cancer and disproportionately accounts for the majority of breast cancer related deaths. Effective treatment of this disease remains an unmet medical need. Over the past several decades, TNBC cell lines have been used as the foundation for drug development and disease modeling. However, ever-mounting research demonstrates striking differences between cell lines and clinical TNBC tumors, disconnecting bench research and actual clinical responses. In this review, we discuss the limitations of cell lines and the importance of using patients' tumors for translational research, and highlight the usage of patient-derived xenograft (PDXs) models that have emerged as a clinically relevant platform for preclinical studies. PDX tumors possess tumor heterogeneity with similar cellular, molecular, genetic and epigenetic properties akin to those found within patients' tumors. Moreover, PDX and clinical tumors possess abnormal vasculature with higher blood vessel permeability, a feature that is not always demonstrated in in vivo cell line xenografts. Development of clinically relevant, novel drug-nanoparticles capable of accumulating in PDX tumors through the enhanced permeability and retention effect in tumor vasculature may lead to new and effective TNBC treatments.

A Method to Encapsulate Small Organic Molecules in Calcium Phosphate Nanoparticles Based on the Supramolecular Chemistry of Cyclodextrin

Calcium phosphate nanoparticles (CPNPs) encapsulating small organic molecules, such as imaging agents and drugs, are considered to be ideal devices for cancer diagnosis or therapy. However, it is generally difficult to encapsulate small organic molecules in CPNPs because of the lack of solubility in water or binding affinity to calcium phosphate. To solve these issues, we utilized the carboxymethyl β-cyclodextrin (CM-β-CD) to increase the solubility and binding affinity to small organic molecules for the encapsulation into CPNPs in this work. The results indicated that the model molecules, hydrophilic rhodamine B (RB) and hydrophobic docetaxel (Dtxl), are successfully encapsulated into CPNPs with the assistance of CM-β-CD. We also demonstrated the CPNPs could be remarkably internalized into A549 cells, resulting in the efficient inhibition of tumor cells' growth.

Tailored design of multifunctional and programmable pH-responsive self-assembling polypeptides as drug delivery nanocarrier for cancer therapy

Breast cancer has become the second leading cause of cancer-related mortality in female wherein more than 90% of breast cancer-related death results from cancer metastasis to distant organs at advanced stage. The purpose of this study is to develop biodegradable nanoparticles composed of natural polypeptides and calcium phosphate (CaP) with sequential pH-responsivity to tumor microenvironments for active targeted drug delivery. Two different amphiphilic copolymers, poly(ethylene glycol)₃₄₀₀-aconityl linkage-poly(l-glutamic acid)₁₅-poly(l-histidine)₁₀-poly(l-leucine)₁₀ and LyP1-poly(ethylene glycol)₁₁₀₀-poly(l-glutamic acid)₁₅-poly(l-histidine)₁₀-poly(l-leucine)₁₀, were exploited to self-assemble into micelles in aqueous phase. The bio-stable nanoparticles provide three distinct functional domains: the anionic PGlu shell for CaP mineralization, the protonation of PHis segment for facilitating anticancer drug release at target site, and the hydrophobic core of PLeu for encapsulation of anticancer drugs. Furthermore, the hydrated PEG outer corona is used for prolonging circulation time, while the active targeting ligand, LyP-1, is served to bind to breast cancer cells and lymphatic endothelial cells in tumor for inhibiting metastasis. Mineralized DOX-loaded nanoparticles (M-DOX NPs) efficiently prevent the drug leakage at physiological pH value and facilitate the encapsulated drug release at acidic condition when compared to DOX-loaded nanoparticles (DOX NPs). M-DOX NPs with LyP-1 targeting ligand effectively accumulated in MDA-MB-231 breast cancer cells. The inhibition effect on cell proliferation also enhances with time, illustrating the prominent anti-tumor efficacy. Moreover, the in vitro metastatic inhibition model shows the profound inhibition effect of inhibitory nanoparticles. In brief, this self-assembling peptide-based drug delivery nanocarrier with multifunctionality and programmable pH-sensitivity is of great promise and potential for anti-cancer therapy.

STATEMENT OF SIGNIFICANCE

This tailored-design polypeptide-based nanoparticles with self-assembling and programmable stimulus-responsive properties enable to 1) have stable pH in physiological value with a low level of drug loss and effectively release the encapsulated drug with pH variations according to the tumor microenvironment, 2) enhance targeting ability to hard-to-treat breast cancer cells and activate endothelial cells (tumor region), 3) significantly inhibit the growth and prevent from malignant metastasis of cancer cells in consonance with promising anti-tumor efficacy, and 4) make tumors stick to localized position so that these confined solid tumors can be more accessible by different treatment modalities. This work contributes to designing a programmable pH-responsive drug delivery system based on the tailor-designed polypeptides.

Delivery of the autofluorescent protein R-phycoerythrin by calcium phosphate nanoparticles into four different eukaryotic cell lines (HeLa, HEK293T, MG-63, MC3T3): Highly efficient, but leading to endolysosomal proteolysis in HeLa and MC3T3 cells

Nanoparticles can be used as carriers to transport biomolecules like proteins and synthetic molecules across the cell membrane because many molecules are not able to cross the cell membrane on their own. The uptake of nanoparticles together with their cargo typically occurs via endocytosis, raising concerns about the possible degradation of the cargo in the endolysosomal system. As the tracking of a dye-labelled protein during cellular uptake and processing is not indicative of the presence of the protein itself but only for the fluorescent label, a label-free tracking was performed with the red-fluorescing model protein R-phycoerythrin (R-PE). Four different eukaryotic cell lines were investigated: HeLa, HEK293T, MG-63, and MC3T3. Alone, the protein was not taken up by any cell line; only with the help of calcium phosphate nanoparticles, an efficient uptake occurred. After the uptake into HeLa cells, the protein was found in early endosomes (shown by the marker EEA1) and lysosomes (shown by the marker Lamp1). There, it was still intact and functional (i.e. properly folded) as its red fluorescence was detected. However, a few hours after the uptake, proteolysis started as indicated by the decreasing red fluorescence intensity in the case of HeLa and MC3T3 cells. 12 h after the uptake, the protein was almost completely degraded in HeLa cells and MC3T3 cells. In HEK293T cells and MG-63 cells, no degradation of the protein was observed. In the presence of Bafilomycin A1, an inhibitor of acidification and protein degradation in lysosomes, the fluorescence of R-PE remained intact over the whole observation period in the four cell lines. These results indicate that despite an efficient nanoparticle-mediated uptake of proteins by cells, a rapid endolysosomal degradation may prevent the desired (e.g. therapeutic) effect of a protein inside a cell.

Mussel-inspired poly(L-DOPA)-templated mineralization for calcium phosphate-assembled intracellular nanocarriers

We developed a calcium phosphate (CaP)-assembled polymer nanocarrier for intracellular doxorubicin (DOX) delivery based on a mussel-inspired mineralization approach. A DOX-loaded core-shell polymer nanoparticle (DOX-NP) consisting of a poly(3,4-dihydroxy-l-phenylalanine) (PDOPA) core and a poly (ethylene glycol) (PEG) shell was utilized as a nanotemplate for CaP mineralization. The mean hydrodynamic diameter of the DOX-loaded CaP-mineralized polymer nanoparticles (DOX-CaP-NPs) was 154.3nm. Energy-dispersive X-ray spectroscopy confirmed that the DOX-CaP-NPs contained substantial amounts of Ca and P, elements found only in the CaP mineral. The loading efficiency and content of DOX, estimated by fluorescence spectroscopy, were 54.0% and 10.8wt%, respectively. The CaP deposited in the PDOPA core domain enabled the DOX-CaP-NPs to maintain a robust structure and effectively inhibit DOX release at extracellular pH, whereas at endosomal pH, the CaP core dissolved to trigger a facilitated DOX release. The DOX-CaP-NPs may serve as robust nanocarriers with a high delivery efficacy for cancer chemotherapy.

Dehydroascorbic Acids-modified Polymer Micelles Target Cancer Cells to Enhance Anti-tumor Efficacy of Paclitaxel

Paclitaxel (PTX), especially albumin-bound PTX in clinical, has displayed significant inhibition of tumor growth in patients. But the systemic distribution and poor water solubility of PTX often lead to severe side effects, consequently limiting the anti-tumor efficacy. In this study, we developed a novel PTX-loaded polymeric micelle drug delivery system. These self-assembled polymeric micelles from core to outside consisted of poly L-phenylalanine (pPhe), DTSSP linked poly L-lysine (pLys), poly ethylene glycol (PEG) and dehydroascorbic acids (DHA). pPhe formed the hydrophobic core to encapsulate PTX; DTSSPs on pLys covalently cross-linked and formed disulfide bond to stabilize PTX from loss in blood circulation; PEG improved solubility to lower toxicity of PTX for its high hydrophilicity; DHA targeted tumors by specifically recognizing GLUT1 mainly expressed on tumor cells. Thus, PTX would be precisely released into tumor cells with high dose of glutathione to break disulfide bond. Moreover, these PTX-loaded polymer micelles significantly suppressed tumor cell viability, proliferation, and migration in vitro, and also greatly inhibited tumor growth and prolonged survival in tumor-bearing mice without detectable side effects. Therefore, the new drug delivery system could reduce severe side effects and enhance anti-tumor efficacy of PTX via peripheral stabilization, low toxicity and tumor targeting.

Strategies for improving the payload of small molecular drugs in polymeric micelles

In the past few years, substantial efforts have been made in the design and preparation of polymeric micelles as novel drug delivery vehicles. Typically, polymeric micelles possess a spherical core-shell structure, with a hydrophobic core and a hydrophilic shell. Consequently, poorly water-soluble drugs can be effectively solubilized within the hydrophobic core, which can significantly boost their drug loading in aqueous media. This leads to new opportunities for some bioactive compounds that have previously been abandoned due to their low aqueous solubility. Even so, the payload of small molecular drugs is still not often satisfactory due to low drug loading and premature release, which makes it difficult to meet the requirements of in vivo studies. This problem has been a major focus in recent years. Following an analysis of the published literature in this field, several strategies towards achieving polymeric micelles with high drug loading and stability are presented in this review, in order to ensure adequate drug levels reach target sites.

Encapsulation of cisplatin in a pegylated calcium phosphate nanoparticle (CPNP) for enhanced cytotoxicity to cancerous cells

HYPOTHESIS

Exchange of the chloride ion (Cl^-) ligands of cisplatin with carboxylates is widely used in fabricating cisplatin loaded nanoparticles for improved cancer therapy. However, the dynamic exchange may cause premature cisplatin release and even disintegration of the nanoparticles in Cl^--containing medium such as in plasma. Molecules bearing carboxylates are capable of mediating the mineralization process of calcium phosphate; therefore, it is possible to overcome the disadvantage by sequestering cisplatin in a calcium phosphate nanoparticle (CPNP).

EXPERIMENTS

With the hypothesis, precipitation reaction of calcium nitrate and disodium hydrogen phosphate was performed in a solution of poly(ethylene glycol)-poly(acrylic acid) block copolymers with their carboxylates partly conjugated with cisplatin. Then, structure, physicochemical properties, and bioactivity of the product were carefully investigated with multiple characterization methods.

FINDINGS

It was revealed a pegylated, cisplatin encapsulated CPNP was prepared; and with appropriate mole ratio of cisplatin to carboxylates, the nanoparticle encapsulated cisplatin efficiently (>90%), was stable and almost entirely prevented the cisplatin release in Cl^--containing medium at pH 7.4 but released them in an acidic condition, and showed moderately and greatly enhanced cytotoxicities to the lung cancer cell line A549 and its cisplatin resistance form A549R respectively in comparison with the free cisplatin.

Humid Heat Autoclaving of Hybrid Nanoparticles Achieved by Decreased Nanoparticle Concentration and Improved Nanoparticle Stability Using Medium Chain Triglycerides as a Modifier

PURPOSE

Humid heat autoclaving is a facile technique widely used in the sterilization of injections, but the high temperature employed would destroy nanoparticles composed of biodegradable polymers. The aim of this study was to investigate whether incorporation of medium chain triglycerides (MCT) could stabilize nanoparticles composed of poly (ethylene glycol)-b-polycaprolactone (PEG-b-PCL) during autoclaving (121°C, 10 min).

METHODS

Polymeric nanoparticles with different MCT contents were prepared by dialysis. Block copolymer degradation was studied by GPC. The critical aggregation concentrations of nanoparticles at different temperatures were determined using pyrene fluorescence. The size, morphology and weight averaged molecular weight of pristine/autoclaved nanoparticles were studied using DLS, TEM and SLS, respectively. Drug loading content and release profile were determined using RP-HPLC.

RESULTS

The protecting effect of MCT on nanoparticles was dependent on the amount of MCT incorporated. Nanoparticles with high MCT contents, which assumed an emulsion-like morphology, showed reduced block copolymer degradation and particle disassociation after incubation at 100°C for 24 h. Nanoparticles with high MCT content showed the lowest critical aggregation concentration (CAC) under either room temperature or 60°C and the lowest particle concentration among all samples. And the particle size, drug loading content, physical stability and release profile of nanoparticles with high MCT contents remained nearly unchanged after autoclaving.

CONCLUSION

Incorporation of high amount of MCT changed the morphology of PEG-b-PCL based nanoparticles to an emulsion-like structure and the nanoparticles prepared could withstand autoclaving due to improved particle stability and decreased particle concentration caused by MCT incorporation.

Nanocarriers for delivery of siRNA and co-delivery of siRNA and other therapeutic agents

A major problem in cancer treatment is the multidrug resistance. siRNA inhibitors have great advantages to solve the problem, if the bottleneck of their delivery could be well addressed by the various nanocarriers. Moreover, co-delivery of siRNA together with the various anticancer agents in one nanocarrier may maximize their additive or synergistic effect. This review provides a comprehensive summary on the state-of-the-art of the nanocarriers, which may include prodrugs, micelles, liposomes, dendrimers, nanohydrogels, solid lipid nanoparticles, nanoparticles of biodegradable polymers and nucleic acid nanocarriers for delivery of siRNA and co-delivery of siRNA together with anticancer agents with focus on synthesis of the nanocarrier materials, design and characterization, in vitro and in vivo evaluation, and prospect and challenges of nanocarriers.

Modification of Spherical Polyelectrolyte Brushes by Layer-by-Layer Self-Assembly as Observed by Small Angle X-ray Scattering

Multilayer modified spherical polyelectrolyte brushes were prepared through alternate deposition of positively charged poly(allylamine hydrochloride) (PAH) and negatively charged poly-l-aspartic acid (PAsp) onto negatively charged spherical poly(acrylic acid) (PAA) brushes (SPBs) on a poly(styrene) core. The charge reversal determined by the zeta potential indicated the success of layer-by-layer (LBL) deposition. The change of the structure during the construction of multilayer modified SPBs was observed by small-angle X-ray scattering (SAXS). SAXS results indicated that some PAH chains were able to penetrate into the PAA brush for the PAA-PAH double-layer modified SPBs whereas part of the PAH moved towards the outer layer when the PAsp layer was loaded to form a PAA-PAH-PAsp triple-layer system. The multilayer modified SPBs were stable upon changing the pH (5 to 9) and ionic strength (1 to 100 mM). The triple-layer modified SPBs were more tolerated to high pH (even at 11) compared to the double-layer ones. SAXS is proved to be a powerful tool for studying the inner structure of multilayer modified SPBs, which can establish guidelines for the a range of potential applications of multilayer modified SPBs.

Mitochondria and nuclei dual-targeted heterogeneous hydroxyapatite nanoparticles for enhancing therapeutic efficacy of doxorubicin

Dual-targeted nanoparticles have been increasingly used to realize greater anti-proliferation effect by attacking double key sites of tumor cells. In order to retain nuclei inhibition effect and enhance DOX-induced apoptosis by mitochondrial pathway simultaneously, hyaluronic acid (HA) modified hydroxyapatite (HAP) nanoparticles (HAP-HA), the functional calcium-based tumor targeting nanoparticles, have been developed. In this nanosystem, HA acts as an active tumor-targeting ligand to bind the CD44 receptors which are overexpressed on the surface of tumor cells while HAP can load and deliver DOX to both nuclei and mitochondria of tumor cells. In this study, DOX-loaded HAP-HA nanoparticles (DOX/HAP-HA) exhibited satisfactory drug loading efficiency which was up to 214.55 ± 51.05 μg mg(-1) and showed a uniform nano-scaled particle size. The mitochondrial and nuclei targetability of DOX/HAP-HA was confirmed by confocal laser scanning microscopy analyses. Besides, western blot assay demonstrated that DOX/HAP-HA could markedly enhance mitochondrial cytochrome C leakage and thereby activate apoptotic cascade associated with it. In addition, in vivo anti-tumor efficacy and toxicity evaluation of DOX/HAP-HA indicated that DOX/HAP-HA was more effective and less harmful compared to other groups. DOX/HAP-HA might be a new promising targeted delivery system for effective cancer therapy.

Photosensitizer-loaded bubble-generating mineralized nanoparticles for ultrasound imaging and photodynamic therapy

In this work, we have developed photosensitizer-loaded bubble-generating calcium carbonate (CaCO₃)-mineralized nanoparticles that have potential for ultrasound imaging (US)-guided photodynamic therapy (PDT) of tumors. A photosensitizer, chlorin e6 (Ce6)-loaded CaCO₃-mineralized nanoparticles (Ce6-BMNs), was prepared using an anionic block copolymer-templated in situ mineralization method. Ce6-BMNs were composed of the Ce6-loaded CaCO₃ core and the hydrated poly(ethylene glycol) (PEG) shell. Ce6-BMNs exhibited excellent stability under serum conditions. Ce6-BMNs showed enhanced echogenic US signals at tumoral acid pH by generating carbon dioxide (CO₂) bubbles. Ce6-BMNs effectively inhibited Ce6 release at physiological pH (7.4). At a tumoral acidic pH (6.4), Ce6 release was accelerated with CO₂ bubble generation due to the dissolution of the CaCO₃ mineral core. Upon irradiation of Ce6-BMN-treated MCF-7 breast cancer cells, the cell viability dramatically decreased with increasing Ce6 concentration. The phototoxicity of the Ce6-BMNs was much higher than that of free Ce6. On the basis of tumoral pH-responsive CO₂ bubble-generation and simultaneous Ce6 release at the target tumor site, these CaCO₃ mineralized nanoparticles can be considered as promising theranostic nanoparticles for US imaging-guided PDT in the field of tumor therapy.