Grafted thermo-responsive gelatin microspheres as delivery systems in triggered drug release

Amoxicillin-loaded polycaprolactone-gelatin nanofiber/net (NFN) matrices for pneumothorax treatment

The recurrence rate of spontaneous pneumothorax (collapsed lung) is 30 % after basic conservative treatments, and it can reach up to 20 % after surgery due to the limited effectiveness of current surgical techniques. This highlights the need for the development of new, effective treatment approaches supported by biomaterials. Therefore, we aimed to develop a biomaterial that does not restrict the aerodynamic movements of the lungs, is resistant to lung pressure, and can withstand the movements during inhalation and exhalation,to prevent and treat pneumothorax recurrence. For this purpose, biodegradable matrices were prepared using polycaprolactone (PCL), gelatin (GEL), and amoxicillin (AMX), which is a broad-spectrum antibiotic. The matrices were designed with a nanofiber/net (NFN) structure, targeting appropriate degradation rates and mechanical strength. NFN matrices with randomly arranged and bead-free fibers were produced by electrospinning PCL/GEL and PCL/GEL-AMX solutions in different ratios. The incorporation of AMX reduced the fiber diameter, while the addition of GEL increased the fiber diameters, resulting in fibrous matrices with diameters ranging from 194 nm to 1,100 nm. Additionally, adding GEL and/or AMX to the structure caused the fiber surfaces to resemble tree bark, and spider web-like nano networks formed between the fibers. These formations were particularly homogeneous and dense in the (7:3) PCL/GEL-5AMX group. Energy dispersive X-ray (EDX) analysis showed that the elemental composition of the fibers and the nano-networks was similar. The elastic moduli of the matrix groups ranged from 3.97 ± 0.74 MPa to 19.02 ± 1.91 MPa, which was found to be suitable for the target range for lung tissue. Hydrolytic degradation studies indicated that nano-networks remained present in the structure after 5 weeks, and 55-68 % of the loaded AMX was released within 14 days. In the AMX-loaded groups, both Escherichia coli (E. coli) and Streptococcus aureus (S. aureus) growth were inhibited, with the most effective inhibition observed in the (7:3) PCL/GEL-5AMX group. In conclusion, it was assessed that the spider web-like nano-networks, which increased with the GEL and AMX ratio in the solution, mimicked the structure of lung alveoli at the nanoscale due to their large surface area and small pore size between the fibers. Particularly, the (7:3) PCL/GEL-5AMX NFN matrix could be used as a new and effective alternative material in pneumothorax therapy.

Formulation development of highly stable collagenase-containing hydrogels for wound healing

Collagenases are enzymes that break down collagen and are used in wound healing and treating various disorders. Currently, collagenase is commercially available in only ointment and injectable forms and is sensitive to various environmental factors. In the present study, different hydrogel formulations of collagenase have been prepared at pH 6.5 using carboxymethylcellulose sodium and zinc acetate with and without humectants such as propylene glycol (PG) and glycerin (GL) in varying concentrations. The formulated gels were stored at room temperature (25±2°C, 60±5% RH) and refrigerator temperature (5±3°C) for six months to evaluate their physical and up to six years for chemical stability. The gels were subjected to various tests, including organoleptic studies, spreadability, moisture content, swelling index, swelling/de-swelling, syneresis, viscosity, gelation time, and weight variation. The purity and molecular weight of collagenase have been determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). At the same time, its activity during the storage period was evaluated by gelatin zymography. Casein zymography was also performed to detect any caseinase contamination in the formulations. The release of the enzyme from different gel formulations was assessed using the Franz diffusion apparatus and analyzed by gelatin zymography. The results showed some physical changes that were more prominent in gels stored at room temperature than those kept refrigerated. The difference in humectant concentration was also found to affect the stability of gels. PG was found to be a better humectant than GL, particularly in a concentration of 25%. The zymography results indicated that collagenase was stable in all formulations kept in the refrigerator. In contrast, its complete degradation was noted in the preparations stored at room temperature within a month. The data generated in this study will help the formulators to commercialize a relatively economical gel formulation of collagenase that is highly stable for up to six years at refrigerator temperature (5±3°C).

Coprecipitation of Class II NSAIDs with Polymers for Oral Delivery

Non-steroidal anti-inflammatory drugs (NSAIDs) are frequently administered orally with modified-release formulations. The attainment of modified-release drugs is commonly achieved through the coprecipitation of the active principle with a biodegradable polymeric carrier in the form of micro or nanoparticles. In this review, some coprecipitation studies of three highly prescribed NSAIDs (in particular, ibuprofen, ketoprofen, and diclofenac sodium) have been analyzed. The techniques employed to micronize the powder, the polymers used, and the main results have been classified according to the type of release required in different categories, such as delayed, immediate, prolonged, sustained, and targeted release formulations. Indeed, depending on the pathology to be treated, it is possible to achieve specific therapeutic objectives, ensuring that the drug is released at a higher or lower dissolution rate (if compared to conventional drugs) and/or at a different time and/or in a specific site of action.

Preparation and Characteristics of Alginate Microparticles for Food, Pharmaceutical and Cosmetic Applications

Alginates are the most widely used natural polymers in the pharmaceutical, food and cosmetic industries. Usually, they are applied as a thickening, gel-forming and stabilizing agent. Moreover, the alginate-based formulations such as matrices, membranes, nanospheres or microcapsules are often used as delivery systems. Alginate microparticles (AMP) are biocompatible, biodegradable and nontoxic carriers, applied to encapsulate hydrophilic active substances, including probiotics. Here, we report the methods most frequently used for AMP production and encapsulation of different actives. The technological parameters important in the process of AMP preparation, such as alginate concentration, the type and concentration of other reagents (cross-linking agents, oils, emulsifiers and pH regulators), agitation speed or cross-linking time, are reviewed. Furthermore, the advantages and disadvantages of alginate microparticles as delivery systems are discussed, and an overview of the active ingredients enclosed in the alginate carriers are presented.

Release of bioactive compounds from delivery systems by stimuli-responsive approaches; triggering factors, mechanisms, and applications

Recent advances in emerging nanocarriers and stimuli-responsive (SR) delivery systems have brought about a revolution in the food and pharmaceutical industries. SR carriers are able to release the encapsulated bioactive compounds (bioactives) upon an external trigger. The potential of releasing the loaded bioactives in site-specific is of great importance for the pharmaceutical industry and medicine that can deliver the cargo in an appropriate condition. For the food industry, release of encapsulated bioactives is considerably important in processing or storage of food products and can be used in their formulation or packaging. There are various stimuli to control the favorite release of bioactives. In this review, we will shed light on the effect of different stimuli such as temperature, humidity, pH, light, enzymatic hydrolysis, redox, and also multiple stimuli on the release of encapsulated cargo and their potential applications in the food and pharmaceutical industries. An overview of cargo release mechanisms is also discussed. Furthermore, various alternatives to manipulate the controlled release of bioactives from carriers and the perspective of more progress in these SR carriers are highlighted.

Thermoresponsive semi-interpenetrating gelatin-alginate networks for encapsulation and controlled release of scent molecules

Plant-based meats, which are nutritious foods from non-animal sources, provide clues for addressing the negative externalities associated with conventional meat production. Interest in plant-based meat has increased and is driving the rapid growth of its market. Plant-based meat should be equipped with a temperature-dependent scent release system similar to the scent release mechanism of conventional meat, to deliver a desirable meat-like flavor to consumers and obtain higher market acceptance. In this study, we prepared thermoresponsive gelatin-alginate hybrid hydrogels to control the release of scent molecules. The polymer network of gelatin-alginate hydrogels was reinforced by a semi-interpenetrating network (sIPN). sIPN formation conferred resistance to external stimuli, such as shear force, swelling, and temperature, resulting in a sustained release of the meat scent. In addition, controlled size microcapsules fabricated from the same composition via an electrostatic extrusion process showed a sustained release pattern of the loaded scent at 70 °C, and the scent release rate was precisely controlled within an approximately 2-fold range by adjusting the alginate concentration. These observations suggest the potential use of edible biological macromolecules as food additives that can control the release of scent molecules from the plant-based meat during cooking.

Grafting of Natural Polymers and Gums for Drug Delivery Applications: A Perspective Review

Natural polymers have received more attention because of their advantages over synthetic polymers such as abundant availability, low cost, biodegradability and non-toxicity. However, natural polymers suffer some limitations such as drop-in viscosity upon storage, uncontrolled hydration, solubility, inability to perform under high temperature and pressure (thermal stability), etc. In many instances above mentioned drawbacks of natural polymers limits their applications in drug delivery systems. Grafting of natural polymer leads to improved properties and characteristics of backbones of macromolecules such as improvement in gel strength, swelling index, mucoadhesion, drug targeting and drug release profile. Therefore, in recent decades grafting of the natural polymer has gained immense importance for the development of drug delivery systems. In addition to the pharmaceutical applications graft copolymers are extensively utilized in diversified fields. The present review is an attempt to define the grafting, various methods of polymer grafting and their application in drug delivery.

Study on preparation, compression strength and theophylline/diclofenac sodium release ability of NIPAAm/DMAPMAAm hydrogels

The present study was undertaken to investigate the effect of the composition of the polymerization medium and the type of drug/drug loading process on the mechanical strengths and release profiles of poly(N-isopropylacrylamide-co-N-[3-(dimethylamino)propyl] methacrylamide) P(NIPAAm-co-DMAPMAAm) hydrogels. In line with this goal firstly, the temperature- and pH-responsive hydrogels of NIPAAm and DMAPMAAm were synthesized in three different media at 60 °C: pH 7.4 phosphate-buffered saline (PBS), pH 7.4 phosphate buffer without NaCl/KCl (PB), and distilled-deionized water (pH ≈ 5.5 DDW). The result is that the presence of anionic species such as phosphate (HPO₄^2-/H₂PO₄^-) and chloride (Cl^-) ions in the solution affects on their basic network properties such as volumetric swelling ratio and compression modulus. To evaluate their intermolecular interactions with protonated DMAPMAAm units and drug molecules, depending on composition, type of loading process and drug structure, each of the hydrogels was loaded with diclofenac sodium (DFNa) and theophylline (Thp) by using both diffusion and in situ loading methods. DFNa and Thp release profiles in pH 7.4 PBS at 37 °C were analysed by using zero-order, first-order, Higuchi, Korsmeyer-Peppas, and Peppas-Sahlin models. It has been observed that for the first 60% of DFNa and Thp releases from P(NIPAAm-co-DMAPMAAm) hydrogels synthesized in PB at 60 °C, the contribution of the chain relaxation for the copolymer hydrogels loaded during gelation process was higher than the ones loaded by diffusion process.

Antioxidant and multi-sensitive PNIPAAm/keratin double network gels for self-stripping wound dressing application

Hydrogel is a potential wound dressing material due to its ability to maintain a humid environment, the strong absorptive capacity of exuded tissue fluid, and gas exchange function. Herein, poly(N-isopropyl acrylamide)/keratin double network (PNIPAAm/keratin DN) gels were fabricated through covalent and ionic double cross-linking strategy. The effects of PNIPAAm/keratin ratios on the morphology and swelling rate of gels were characterized. The DN gels could swell up from 2600% to 4600% in proportion to the keratin content, demonstrating their great ability to absorb tissue fluid. The gels possessed thermo-sensitiveness, imparting self-stripping property. Moreover, the antibacterial chlorhexidine acetate (CHX) was loaded into gels with a post-fabrication drug-loading strategy. The release behavior showed that CHX-loaded DN gels exhibited multiple responsive characteristics (temperature, pH, and ROS). Furthermore, the drug-loaded gels showed greater antibacterial activity than free CHX due to the sustained drug release effect. Meanwhile, the antioxidant efficiency of PNIPAAm/keratin DN gels was ca. 33.1%, while the PNIPAAm gel was just ca. 18.2%, indicating the strong oxidation resistance of DN gels. In the Sprague Dawley (SD) rat skin defect model, the hydrogel had better tissue regeneration ability than the commercial film. Taken together, the multifunctional PNIPAAm/keratin DN gels are potential candidates for clinical wound treatment.

Smart gating porous particles as new carriers for drug delivery

The design of smart drug delivery carriers has recently attracted great attention in the biomedical field. Smart carriers can specifically respond to physical and chemical changes in their environment, such as temperature, photoirradiation, ultrasound, magnetic field, pH, redox species, and biomolecules. This review summarizes recent advances in the integration of porous particles and stimuli-responsive gatekeepers for effective drug delivery. Their unique structural properties play an important role in facilitating the diffusion of drug molecules and cell attachment. Various techniques for fabricating porous materials, with their major advantages and limitations, are summarized. Smart gatekeepers provide advanced functions such as "open-close" switching by functionalized stimuli-responsive polymers on a particle's pores. These controlled delivery systems enable drugs to be targeted at specific rates, time programs, and sites of the human body. The gate structures, gating mechanisms, and controlled release mechanisms of each trigger are detailed. Current ongoing research and future trends in targeted drug delivery, tissue engineering, and regenerative medicine applications are highlighted.

Multi-Component Hydrogel Beads Incorporated with Reduced Graphene Oxide for pH-Responsive and Controlled Co-Delivery of Multiple Agents

The development of combination therapy has received great attention in recent years because of its potential to achieve higher therapeutic efficacy than that achieved by mono-drug therapy. Carriers for effective and stimuli-responsive co-delivery of multiple agents, however, are highly deficient at the moment. To address this need, this study reports the generation of multi-component hydrogel beads incorporated with reduced graphene oxide (rGO). The beads are prepared by incorporating doxorubicin (DOX)-loaded gelatine (GL) microbeads into hydrogel beads containing rGO and 5-fluorouracil (5-FU). rGO-containing beads are shown to be more effective in inhibiting the growth of MCF-7 cells via the induction of reactive oxygen species (ROS) generation. In addition, the drug release sustainability of the beads is affected by the pH of the release medium, with the release rate increasing in neutral pH but decreasing in the acidic environment. Our beads warrant further development as carriers for pH-responsive and controlled co-delivery of multiple agents.

Preparation of a size selective nanocomposite through temperature assisted co-assembly of gelatin and pluronic F127 for passive targeting of doxorubicin

The study demonstrates the importance of the weight ratio of F127 and gelatin in forming size selective nanoconjugate through a thermal relaxation approach and its potential as an efficient drug delivery system of doxorubicin with reduced side effects.

Cellular Orientation on Repeatedly Stretching Gelatin Hydrogels with Supramolecular Cross-Linkers

The cytocompatibility of biological and synthetic materials is an important issue for biomaterials. Gelatin hydrogels are used as biomaterials because of their biodegradability. We have previously reported that the mechanical properties of gelatin hydrogels are improved by cross-linking with polyrotaxanes, a supramolecular compound composed of many cyclic molecules threaded with a linear polymer. In this study, the ability of gelatin hydrogels cross-linked by polyrotaxanes (polyrotaxane–gelatin hydrogels) for cell cultivation was investigated. Because the amount of polyrotaxanes used for gelatin fabrication is very small, the chemical composition was barely altered. The structure and wettability of these hydrogels are also the same as those of conventional hydrogels. Fibroblasts adhered on polyrotaxane–gelatin hydrogels and conventional hydrogels without any reduction or apoptosis of adherent cells. From these results, the polyrotaxane–gelatin hydrogels have the potential to improve the mechanical properties of gelatin without affecting cytocompatibility. Interestingly, when cells were cultured on polyrotaxane–gelatin hydrogels after repeated stress deformation, the cells were spontaneously oriented to the stretching direction. This cellular response was not observed on conventional hydrogels. These results suggest that the use of a polyrotaxane cross-linking agent can not only improve the strength of hydrogels but can also contribute to controlling reorientation of the gelatin.

Injectable Hydrogels for Cancer Therapy over the Last Decade

The interest in injectable hydrogels for cancer treatment has been significantly growing over the last decade, due to the availability of a wide range of starting polymer structures with tailored features and high chemical versatility. Many research groups are working on the development of highly engineered injectable delivery vehicle systems suitable for combined chemo-and radio-therapy, as well as thermal and photo-thermal ablation, with the aim of finding out effective solutions to overcome the current obstacles of conventional therapeutic protocols. Within this work, we have reviewed and discussed the most recent injectable hydrogel systems, focusing on the structure and properties of the starting polymers, which are mainly classified into natural or synthetic sources. Moreover, mapping the research landscape of the fabrication strategies, the main outcome of each system is discussed in light of possible clinical applications.

Injectable scaffolds: Preparation and application in dental and craniofacial regeneration

Injectable scaffolds are appealing for tissue regeneration because they offer many advantages over pre-formed scaffolds. This article provides a comprehensive review of the injectable scaffolds currently being investigated for dental and craniofacial tissue regeneration. First, we provide an overview of injectable scaffolding materials, including natural, synthetic, and composite biomaterials. Next, we discuss a variety of characteristic parameters and gelation mechanisms of the injectable scaffolds. The advanced injectable scaffolding systems developed in recent years are then illustrated. Furthermore, we summarize the applications of the injectable scaffolds for the regeneration of dental and craniofacial tissues that include pulp, dentin, periodontal ligament, temporomandibular joint, and alveolar bone. Finally, our perspectives on the injectable scaffolds for dental and craniofacial tissue regeneration are offered as signposts for the future advancement of this field.

On the importance of Bloom number of gelatin to the development of biodegradable in situ gelling copolymers for intracameral drug delivery

To overcome the drawbacks associated with conventional antiglaucoma eye drops, this work demonstrated the feasibility of an effective alternative strategy to administer pilocarpine directly via intracameral injections of drug-containing biodegradable in situ gelling GN copolymers composed of gelatin and poly(N-isopropylacrylamide). Specifically, this study aims to understand the importance of Bloom number of gelatin, a physicochemical parameter, to the development of GN carriers for intracameral drug delivery in glaucoma therapy. Our results showed that both imino acid and triple-helix contents increased with increasing Bloom index from 75-100 to 300. The drug encapsulation efficiency in response to temperature-triggered phase transition in GN copolymers was affected by the Bloom index of gelatin. In addition, the differences in protein secondary structure significantly influenced the degradation rates of GN carriers, which were highly correlated with drug release profiles. The increase in released pilocarpine concentration led to a high intracellular calcium level in rabbit ciliary smooth muscle cell cultures, indicating a beneficial pharmacological response to a drug. Irrespective of Bloom number of gelatin, all carrier materials exhibited excellent in vitro and in vivo biocompatibility with corneal endothelium. In a glaucomatous rabbit model, intracameral injections of pilocarpine-containing GN synthesized from gelatins with various Bloom numbers had different abilities to improve ocular hypertension and induce pupillary constriction, indicating distinct antiglaucoma efficacies due to in vivo drug release. It is concluded that the effects on pharmacological treatment using GN carriers for intracameral pilocarpine administration demonstrate a strong dependence on the Bloom number of gelatin.

Recent progresses in bioadhesive microspheres via transmucosal administration

Based on the advantages of adhesion preparations and the application status of microspheres (MSs) in mucous delivery, this paper primarily reviews the bioadhesive MSs via transmucosal administration routes, including the mucosa in alimentary tract and other lumens. Particularly, the detailed researches about of celladhesive MSs and some new-style bioadhesive MSs are mentioned. Furthermore, this review attempts to reveal the advances of bioadhesive MSs as cell-selective bioadhesion systems and the stimuli-responsive MSs as location-specific drug delivery systems. Although these MSs show powerful strength, some far-sighted ideas should be brought on agendas. In the future, mechanisms should be put under tight scrutiny and more attention should be focused on the excellent bioadhesive materials and the 'second generation mucoadhesives'. Meaningful clinical applications of these novel MSs are also of current concerns and need more detailed researches.

Hydrophobically Modified Keratin Vesicles for GSH-Responsive Intracellular Drug Release

Redox-responsive polymersomes were prepared by self-assembly of a hydrophobically modified keratin and employing a water addition/solvent evaporation method. Polyethylene glycol-40 stearate (PEG40ST) was chosen as hydrophobic block to be coupled to keratin via radical grafting. The amphiphilic polymer exhibited low critical aggregation concentration (CAC; 10 μg/mL), indicating a good thermodynamic stability. The polymeric vesicles loaded both hydrophilic methotrexate and hydrophobic curcumin with high entrapment efficiencies, and showed a GSH-dependent drug release rate. Confocal studies on HeLa cells revealed that the obtained polymersomes were efficiently internalized. Biocompatibility properties of the proposed delivery vehicle were assessed in HET-CAM test and Balb-3T3 mouse fibroblasts. Polymersomes loaded with either methotrexate or curcumin inhibited HeLa and CHO-K1 cancer cells proliferation. Overall, the proposed keratin polymersomes could be efficient nanocarriers for chemotherapeutic agents.

Magnetic hyaluronic acid nanospheres via aqueous Diels-Alder chemistry to deliver dexamethasone for adipose tissue engineering

Biopolymer-based nanospheres have great potential in the field of drug delivery and tissue regenerative medicine. In this work, we present a flexible way to conjugate a magnetic hyaluronic acid (HA) nanosphere system that are capable of vectoring delivery of adipogenic factor, e.g. dexamethasone, for adipose tissue engineering. Conjugation of nanospheres was established by aqueous Diels-Alder chemistry between furan and maleimide of HA derivatives. Simultaneously, a furan functionalized dexamethasone peptide, GQPGK, was synthesized and covalently immobilized into the nanospheres. The magnetic HA nanospheres were fabricated by encapsulating super-paramagnetic iron oxide nanoparticles, which exhibited quick magnetic sensitivity. The aqueous Diels-Alder chemistry made nanospheres high binding efficiency of dexamethasone, and the vectoring delivery of dexamethasone could be easily controlled by a external magnetic field. The potential application of the magnetic HA nanospheres on vectoring delivery of adipogenic factor was confirmed by co-culture of human adipose-derived stem cells (ASCs). In vitro cytotoxicity tests demonstrated that incorporation of dexamethasone into magnetic HA nanospheres showed high efficiency to promote ASCs viabilities, in particular under a magnetic field, which suggested a promising future for adipose regeneration applications.

Coated biodegradable casein nanospheres: a valuable tool for oral drug delivery

Biodegradable casein nanospheres for the sustained release of bioactive molecules in the gastro-intestinal tract were prepared by precipitation polymerization using sodium methacrylate (NaMA) and N,N'-methylene bis-acrylamide (MEBA) as pH-responsive monomer and cross-linker. Three materials with different casein amount were obtained and characterized by scanning electron microscopy, dimensional analysis, water uptake, cytotoxicity and enzymatic degradation experiments. Nanospheres biodegradability was tuned by coating with polyacrylic acid. Coated and uncoated materials were investigated as delivery vehicles for diclofenac sodium salt. For un-coated samples, the release raise 100% in 30 h, while for coated specimens these values were lower than 70%, due to the diffusional constraints of polymer layer.

Concentrated gelatin/alginate composites for fabrication of predesigned scaffolds with a favorable cell response by 3D plotting

Developed concentrated gelatin/alginate with/without HAP composites were plotted into pre-designed scaffolds, which showed good cells attachments and penetration.

Synthesis of pH-responsive hydrogel thin films grafted on PCL substrates for protein delivery

A new visible light induced graft polymerization method was utilized to prepare pH-sensitive hydrogel layers covalently attached to polymer substrates for drug delivery.

Dual-responsive polymer-coated iron oxide nanoparticles for drug delivery and imaging applications

We reported the synthesis and characterization of dual-responsive poly(N-isopropylacrylamide-acrylamide-chitosan) (PAC)-coated magnetic nanoparticles (MNPs) for controlled and targeted drug delivery and imaging applications. The PAC-MNPs size was about 150nm with 70% iron mass content and excellent superparamagnetic properties. PAC-MNPs loaded with anti-cancer drug doxorubicin showed dual-responsive drug release characteristics with the maximum release of drugs at 40°C (∼78%) than at 37°C (∼33%) and at pH of 6 (∼55%) than at pH of 7.4 (∼28%) after 21 days. Further, the conjugation of prostate cancer-specific R11 peptides increased the uptake of PAC-MNPs by prostate cancer PC3 cells. The dose-dependent cellular uptake of the nanoparticles was also significantly increased with the presence of 1.3T magnetic field. The nanoparticles demonstrated cytocompatibility up to concentrations of 500μg/ml when incubated over a period of 24h with human dermal fibroblasts and normal prostate epithelial cells. Finally, pharmacokinetic studies indicated that doxorubicin-loaded PAC-MNPs caused significant prostate cancer cell death at 40°C than at 37°C, thereby confirming the temperature-dependent drug release kinetics and in vitro therapeutic efficacy. Future evaluation of in vivo therapeutic efficacy of targeted image-guided cancer therapy using R11-PAC-MNPs will reinforce a significant impact of the multifunctional PAC-MNPs on the future drug delivery systems.

Stable RNA nanoparticles as potential new generation drugs for cancer therapy

Human genome sequencing revealed that only ~1.5% of the DNA sequence coded for proteins. More and more evidence has uncovered that a substantial part of the 98.5% so-called "junk" DNAs actually code for noncoding RNAs. Two milestones, chemical drugs and protein drugs, have already appeared in the history of drug development, and it is expected that the third milestone in drug development will be RNA drugs or drugs that target RNA. This review focuses on the development of RNA therapeutics for potential cancer treatment by applying RNA nanotechnology. A therapeutic RNA nanoparticle is unique in that its scaffold, ligand, and therapeutic component can all be composed of RNA. The special physicochemical properties lend to the delivery of siRNA, miRNA, ribozymes, or riboswitches; imaging using fluogenenic RNA; and targeting using RNA aptamers. With recent advances in solving the chemical, enzymatic, and thermodynamic stability issues, RNA nanoparticles have been found to be advantageous for in vivo applications due to their uniform nano-scale size, precise stoichiometry, polyvalent nature, low immunogenicity, low toxicity, and target specificity. In vivo animal studies have revealed that RNA nanoparticles can specifically target tumors with favorable pharmacokinetic and pharmacodynamic parameters without unwanted accumulation in normal organs. This review summarizes the key studies that have led to the detailed understanding of RNA nanoparticle formation as well as chemical and thermodynamic stability issue. The methods for RNA nanoparticle construction, and the current challenges in the clinical application of RNA nanotechnology, such as endosome trapping and production costs, are also discussed.

Fabrication of pRNA nanoparticles to deliver therapeutic RNAs and bioactive compounds into tumor cells

RNA nanotechnology is a term that refers to the design, fabrication and use of nanoparticles that are mainly composed of RNAs via bottom-up self-assembly. The packaging RNA (pRNA) of the bacteriophage phi29 DNA packaging motor has been developed into a nanodelivery platform. This protocol describes the synthesis, assembly and functionalization of pRNA nanoparticles on the basis of three 'toolkits' derived from pRNA structural features: interlocking loops for hand-in-hand interactions, palindrome sequences for foot-to-foot interactions and an RNA three-way junction for branch extension. siRNAs, ribozymes, aptamers, chemical ligands, fluorophores and other functionalities can also be fused to the pRNA before the assembly of the nanoparticles, so as to ensure the production of homogeneous nanoparticles and the retention of appropriate folding and function of the incorporated modules. The resulting self-assembled multivalent pRNA nanoparticles are thermodynamically and chemically stable, and they remain intact at ultralow concentrations. Gene-silencing effects are progressively enhanced with increasing numbers of siRNAs in each pRNA nanoparticle. Systemic injection of the pRNA nanoparticles into xenograft-bearing mice has revealed strong binding to tumors without accumulation in vital organs or tissues. The pRNA-based nanodelivery scaffold paves a new way for nanotechnological application of pRNA-based nanoparticles for disease detection and treatment. The time required for completing one round of this protocol is 3-4 weeks when including in vitro functional assays, or 2-3 months when including in vivo studies.

Naturally and synthetic smart composite biomaterials for tissue regeneration

The development of smart biomaterials for tissue regeneration has become the focus of intense research interest. More opportunities are available by the composite approach of combining the biomaterials in the form of biopolymers and/or bioceramics either synthetic or natural. Strategies to provide smart capabilities to the composite biomaterials primarily seek to achieve matrices that are instructive/inductive to cells, or that stimulate/trigger target cell responses that are crucial in the tissue regeneration processes. Here, we review in-depth, recent developments concerning smart composite biomaterials available for delivery systems of biofactors and cells and scaffolding matrices in tissue engineering. Smart composite designs are possible by modulating the bulk and surface properties that mimic the native tissues, either in chemical (extracellular matrix molecules) or in physical properties (e.g. stiffness), or by introducing external therapeutic molecules (drugs, proteins and genes) within the structure in a way that allows sustainable and controllable delivery, even time-dependent and sequential delivery of multiple biofactors. Responsiveness to internal or external stimuli, including pH, temperature, ionic strength, and magnetism, is another promising means to improve the multifunctionality in smart scaffolds with on-demand delivery potential. These approaches will provide the next-generation platforms for designing three-dimensional matrices and delivery systems for tissue regenerative applications.

Diisocyanate mediated polyether modified gelatin drug carrier for controlled release

Gelatin is an extensively studied biopolymer hydrogel drug carrier due to its biocompatibility, biodegradability and non-toxicity of its biodegraded products formed in vivo. But with the pristine gelatin it is difficult to achieve a controlled and desirable drug release characteristics due to its structural and thermal lability and high solubility in aqueous biofluids. Hence it is necessary to modify its solubility and structural stability in biofluids to achieve controlled release features with improved drug efficacy and broader carrier applications. In the present explorations an effort is made in this direction by cross linking gelatin to different extents using hitherto not studied isocyanate terminated poly(ether) as a macrocrosslinker prepared from poly(ethylene glycol) and isophorone diisocyanate in dimethyl sulfoxide. The crosslinked samples were analyzed for structure by Fourier transform-infrared spectroscopy, thermal behavior through thermogravimetric analysis and differential scanning calorimetry. The cross linked gelatins were biodegradable, insoluble and swellable in biofluids. They were evaluated as a carrier for in vitro drug delivery taking theophylline as a model drug used in asthma therapy. The crosslinking of gelatin decreased the drug release rate by 10-20% depending upon the extent of crosslinking. The modeled drug release characteristics revealed an anomalous transport mechanism. The release rates for ampicillin sodium, 5-fluorouracil and theophylline drugs in a typical crosslinked gelatin carrier were found to depend on the solubility and hydrophobicity of the drugs, and the pH of the fluid. The observed results indicated that this material can prove its mettle as a viable carrier matrix in drug delivery applications.