Calcium phosphate-reinforced photosensitizer-loaded polymer nanoparticles for photodynamic therapy

A review of advanced nanoformulations in phototherapy for cancer therapeutics

Phototherapy has the potential to play a greater role in oncology. Phototherapy converts light energy into either chemical energy or thermal energy, which eventually destroys cancer cells after a series of biological reactions. With nanotechnology applications in cancer therapeutics, it has become possible to prepare smart drug carriers with multifunctional properties at the nanoscale level. These nanocarriers may be able to deliver the drug molecules to the target site more efficiently in the form of nanoparticles. Several intrinsic and extrinsic properties of these nanocarriers help target the tumor cells exclusively, and by utilizing these features, drug molecules can be delivered to the tumor cells specifically, which results in high tumor uptake and better therapeutic effects ultimately. Nanocarriers can also be designed to carry different drugs together to provide a platform for combination therapy like chemo-photodynamic therapy and chemo-photodynamic-photothermal therapy. In combination therapy, co-delivery of all different drugs is crucial to obtain their synergistic effects, and with the help of nanocarriers, it is possible to co-deliver these drugs by loading them together onto the nanocarriers.

Biomineralization: An Opportunity and Challenge of Nanoparticle Drug Delivery Systems for Cancer Therapy

Biomineralization is a common process in organisms to produce hard biomaterials by combining inorganic ions with biomacromolecules. Multifunctional nanoplatforms are developed based on the mechanism of biomineralization in many biomedical applications. In the past few years, biomineralization-based nanoparticle drug delivery systems for the cancer treatment have gained a lot of research attention due to the advantages including simple preparation, good biocompatibility, degradability, easy modification, versatility, and targeting. In this review, the research trends of biomineralization-based nanoparticle drug delivery systems and their applications in cancer therapy are summarized. This work aims to promote future researches on cancer therapy based on biomineralization. Rational design of nanoparticle drug delivery systems can overcome the bottleneck in the clinical transformation of nanomaterials. At the same time, biomineralization has also provided new research ideas for cancer treatment, i.e., targeted therapy, which has significantly better performance.

The Significance and Utilisation of Biomimetic and Bioinspired Strategies in the Field of Biomedical Material Engineering: The Case of Calcium Phosphat-Protein Template Constructs

This review provides a summary of recent research on biomimetic and bioinspired strategies applied in the field of biomedical material engineering and focusing particularly on calcium phosphate-protein template constructs inspired by biomineralisation. A description of and discussion on the biomineralisation process is followed by a general summary of the application of the biomimetic and bioinspired strategies in the fields of biomedical material engineering and regenerative medicine. Particular attention is devoted to the description of individual peptides and proteins that serve as templates for the biomimetic mineralisation of calcium phosphate. Moreover, the review also presents a description of smart devices including delivery systems and constructs with specific functions. The paper concludes with a summary of and discussion on potential future developments in this field.

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.

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.

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.

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.

Calcium phosphate-based organic-inorganic hybrid nanocarriers with pH-responsive on/off switch for photodynamic therapy

Photodynamic therapy (PDT) is a promising treatment modality for malignant tumors in a light-selective manner. To improve the PDT efficacy, numerous kinds of nanocarriers have been developed to deliver photosensitizers (PSs) selectively into the tumor through leaky tumor-associated vasculature. However, the corresponding prolonged retention of the nanocarrier in the bloodstream may lead to unfavorable photochemical damage to normal tissues such as skin. Here, we report an organic-inorganic hybrid nanocarrier with a pH-responsive on/off switch of PDT efficacy. This hybrid nanocarrier is constructed by hydrothermal synthesis after simple mixing of calcium/phosphate ions, chlorin e6 (amphiphilic low molecular weight PS), and poly(ethylene glycol)-b-poly(aspartic acid) (PEG-PAsp) copolymers in an aqueous solution. The hybrid nanocarrier possesses a calcium phosphate (CaP) core encapsulating the PSs, which is surrounded by a PEG shielding layer. Under physiological conditions (pH 7.4), the nanocarrier suppressed the photochemical activity of PS by lowering the access of oxygen molecules to the incorporated PS, while PDT efficacy was restored in a pH-responsive manner because of the dissolution of CaP and eventual recovery of access between the oxygen and the PS. Owing to this switch, the nanocarrier reduced the photochemical damage in the bloodstream, while it induced effective PDT efficacy inside the tumor cell in response to the acidic conditions of the endo-/lysosomes.

Developments in PDT Sensitizers for Increased Selectivity and Singlet Oxygen Production

Photodynamic therapy (PDT) is a minimally-invasive procedure that has been clinically approved for treating certain types of cancers. This procedure takes advantage of the cytotoxic activity of singlet oxygen (¹O₂) and other reactive oxygen species (ROS) produced by visible and NIR light irradiation of dye sensitizers following their accumulation in malignant cells. The main two concerns associated with certain clinically-used PDT sensitizers that have been influencing research in this arena are low selectivity toward malignant cells and low levels of ¹O₂ production in aqueous media. Solving the selectivity issue would compensate for photosensitizer concerns such as dark toxicity and aggregation in aqueous media. One main approach to enhancing dye selectivity involves taking advantage of key methods used in pharmaceutical drug delivery. This approach lies at the heart of the recent developments in PDT research and is a point of emphasis in the present review. Of particular interest has been the development of polymeric micelles as nanoparticles for delivering hydrophobic (lipophilic) and amphiphilic photosensitizers to the target cells. This review also covers methods employed to increase ¹O₂ production efficiency, including the design of two-photon absorbing sensitizers and triplet forming cyclometalated Ir(III) complexes.

Cytocompatibility, gene-expression profiling, apoptotic, mechanical and (29)Si, (31)P solid-state nuclear magnetic resonance studies following treatment with a bioglass-chitosan composite

The performance therapy of chitosan (CH)-doped bioactive glass (BG) has been evaluated in vitro and in vivo. In vitro, the effect of CH-BG was assessed on human Saos-2 osteoblast cells. In vivo, Wistar rats were ovariectomized (OVX) and CH, BG and CH-BG were implanted in bone tissue. After 3 days of CH-BG contact, cell viability of Saos-2 osteoblast increased by 16.4% as compared to the control group. The runt-related transcription factor 2 (RUNX2/Cbfa1) and osteocalcin (OC) gene expressions were significantly increased with 600 and 300%, respectively, in contact of CH-BG as compared with CH. In vivo, the apoptotic index in the OVX-CH-BG group was decreased by 80%. A mechanical hardness test showed a significant bone strength improvement after CH-BG implantation (40%). The CH-BG composite may therefore prove clinically useful as a bioactive bone substitute.