In-situ gel: A smart carrier for drug delivery

In-situ gel technology is a promising drug delivery strategy that undergoes a 'sol to gel' transition upon administration, providing controlled and prolonged drug release. These gels are composed of cross-linked 3D networks of polymers, with hydrogels being a specific type of absorbing water while retaining their shape. Gelation can be triggered by various stimuli, such as temperature, pH, ions, and light. They offer several advantages like improved patient compliance, extended drug residence time, localized drug delivery, etc, but also have some disadvantages like drug degradation and limited mechanical strength. In-situ gel falls into three categories: temperature-sensitive, ion-sensitive, and pH-sensitive, but multi-responsive gels that respond to multiple stimuli have better drug release characteristics. The mechanism of in-situ gel formation involves physical and chemical mechanisms. There are various applications of in-situ gel, like ocular drug delivery, nose-to-brain delivery, etc. In this review, we have discussed the types, and mechanisms of in-situ gel & use of in-situ gel in the treatment of different diseases through various routes like buccal, vaginal, ocular, nasal, etc., along with its use in targeted drug delivery.

Ion-activated In Situ Gel of Gellan Gum Containing Chrysin for Nasal Administration in Parkinson's Disease

INTRODUCTION

This study focused on creating an innovative treatment approach for Parkinson's disease (PD), a progressive neurodegenerative condition characterized by the loss of specific neurons in the brain.

AIM

The research aimed to develop a nasal gel using gellan gum containing a complex of chrysin with hydroxypropyl-β-cyclodextrin (HP-β-CD) to enhance the drug's solubility and stability.

METHOD

The formulation process involved utilizing central composite design (CCD) to optimize the concentrations of gellan gum and HPMC E5, with viscosity and mucoadhesive strength as key factors. The resulting optimized in situ gel comprised 0.7% w/v gellan gum and 0.6% w/v HPMC E5, exhibiting desirable viscosity levels for both sol and gel states, along with robust mucoadhesive properties. The formulated gel underwent comprehensive evaluation, including assessments for gelation, drug content, in vitro drug release, ex vivo permeation, and histopathology.

RESULT

The findings demonstrated superior drug release from the in situ gel compared to standalone chrysin. Ex vivo studies revealed effective drug permeation through nasal mucosa without causing harm. Moreover, experiments on neuronal cells exposed to oxidative stress (H2O2- induced) showcased significant neuroprotection conferred by chrysin and its formulations. These treatments exhibited notable enhancements in cell viability and reduced instances of apoptosis and necrosis, compared to the control group. The formulations exhibited neuroprotective properties by mitigating oxidative damage through mechanisms, like free radical scavenging and restoration of antioxidant enzyme activity.

CONCLUSION

In conclusion, this developed in situ gel formulation presents a promising novel nasal delivery system for PD therapy. By addressing challenges related to drug properties and administration route, it holds the potential to enhance treatment outcomes and improve the quality of life for individuals with Parkinson's disease.

Green polymer altered in-situ gel oral liquid sustainable release preparation of vildagliptin suitable for dysphagic diabetic patients: assessment in-vitro & in-vivo

PURPOSE

This work aimed to fabricate alginate based in-situ gelling matrix of vildagliptin improved by calcium and carboxy methyl cellulose (CMC) for appropriate adjustment of the onset and duration of action. This easy-to-swallow thickened liquid preparation aimed to improve compliance for dysphagic or elderly diabetic patients.

METHODS

Vildagliptin dispersions containing alginate were fabricated in the presence or absence of calcium chloride to assess the effect of calcium ion, then a matrix containing 1.5% w/v of sodium alginate with calcium was further examined after the addition of CMC with different concentrations ranging from 0.1% to 0.3%. The viscosity, gelling forming property, Differential scanning calorimetry, and in-vitro drug release were assessed before monitoring the hypoglycemic effect of the selected formulation.

RESULTS

In-situ gel matrixes were fabricated at gastric pH with and without calcium ions. The best formula concerning viscosity and the gel-forming property was achieved with higher CMC concentrations, which in turn decreased the rate of vildagliptin release in stimulated gastric pH. In-vivo results confirmed the extended hypoglycemic effect of the vildagliptin in-situ gelling matrix compared to the vildagliptin aqueous solution.

CONCLUSION

This study represents a green polymeric-based in-situ gel as a liquid oral retarded release preparation intended for reducing dose frequency, easier administration of vildagliptin, and improving compliance in geriatric and dysphagic diabetic patients.

Intra-articular delivery system of methotrexate for rheumatoid arthritis therapy: An in-suit thermosensitive comprehensive gel of polysaccharide from Aconitum carmichaelii Debx

The polysaccharides (FP) extracted from the lateral roots of Aconitum carmichaelii Debx. (Fuzi) are natural compounds, which have effective therapy for rheumatoid arthritis (RA). Methotrexate (MTX) is the first-line drug for RA, but its application is greatly limited to the toxicity in liver and kidney and drug resistance. In this study, an attempt is made to apply oxidized FP (OFP) as a polymer carrier based on intra-articular delivery system loaded MTX. The FP could be developed and used as comprehensive gel carriers with biocompatibility and degradability for therapy of RA. Firstly, OFP-chitosan-poloxamer 407 (OFP-CS-F407-MTX) gel was prepared by natural non-toxic cross-linking agents. Physicochemical characterization was performed by using ¹H NMR and FTIR spectroscopic techniques to assess the successful functionalization of OFP. TGA, SEM and rheological experiment of OFP-CS-F407-MTX gel were investigated. Notably, we loaded MTX into OFP-CS-F407-MTX gel which had remarkable therapeutic efficacy and biosafety for RA. Based on advantages of intra-articular injection of OFP-CS-F407-MTX gel releasing MTX, it modulated proinflammatory cytokines by down-regulating TNF-α, IL-6 and IL-1β expression. Therefore, OFP-CS-F407-MTX in situ gel delivery system can potentially reduce systemic toxicity and irritation of oral administration of MTX but give a controlled release of drug for a long period of time.

Enhancement of in-vitro anti-oral cancer activities of silymarin using dispersion of nanostructured lipid carrier in mucoadhesive in-situ gel

Silymarin (SME) shows multiple therapeutic actions against several cancers, however, low aqueous solubility and poor bioavailability issues restrict its clinical use. In this study, SME was loaded in nanostructured lipid carriers (NLCs) and further incorporated in mucoadhesive in-situ gel (SME-NLCs-Plx/CP-ISG) for localized treatment of oral cancer. Using a 3³ Box-Behnken design (BBD), an optimized SME-NLC formula was developed with the ratios of solid lipids, surfactant concentration, and sonication time as independent variables, while particle size (PS), polydispersity index (PDI), and % encapsulation efficiency (EE) as dependent variables, resulting in 315.5 ± 0.1 nm PS, 0.341 ± 0.01 PDI, and 71.05 ± 0.05 % EE. Structural studies confirmed the formation of SME-NLCs. SME-NLCs incorporated in-situ gel demonstrated a sustained release for SME, indicating enhanced retention on the buccal mucosal membrane. The in-situ gel containing SME-NLCs showed a marked decrease in IC₅₀ value (24.90 ± 0.45 µM) than SME-NLCs (28.40 ± 0.89 µM) and plain SME (36.60 ± 0.26 µM). The studies demonstrated that Reactive oxygen species (ROS) generation potential and SME-NLCs-Plx/CP-ISG induced apoptosis at Sub-G0 phase owing to higher penetration of SME-NLCs led to higher inhibition against human KB oral cancer cells. Therefore, SME-NLCs-Plx/CP-ISG can be the alternative to chemotherapy and surgery with site-specific delivery of SME to oral cancer patients.

Process optimization of Ca2+ cross-linked alginate-based swellable microneedles for enhanced transdermal permeability: More applicable to acidic drugs

We describe a swellable microneedle (SMN) consisting of Ca²⁺ cross-linked alginate, which expands the types of natural polymers available for SMN fabrication. After investigation of different fabrication methods, the alginate in situ hydrogel-based SMN with a flat substrate was successfully constructed, whose gelation was triggered by ethylenediaminetetraacetic acid calcium disodium salt and D-(+)-glucono-1,5-lactone. With the addition of polyvinyl alcohol and trehalose, SMN possessed good mechanical properties. The biocompatibility of SMN was demonstrated through the tests of in vitro cytotoxicity and in vivo skin irritation. With the assistance of SMN, the in vitro transdermal delivery efficiencies of drugs were significantly improved throughout 16 h. 3-O-ethyl ascorbic acid (EAA, pH = 4.81) exhibited a cumulative release of up to 83.83 ± 6.30%, which was consistent with zero-order kinetics, while tranexamic acid (TA, pH = 6.90) showed the most significant increase in delivery efficiency, which was consistent with the Higuchi model and Ritger-Peppas model. The SMN remained intact after the 16 h of EAA transdermal delivery, indicating its better suitability for acidic drugs. We believe that this technology has the potential to expand the range of drugs available for transdermal administration as well as the breadth of patient care applications.

Development of Zoledronic Acid Containing Biomaterials for Enhanced Guided Bone Regeneration

In recent years, biomaterial-based treatments, also called guided bone regeneration (GBR), which aim to establish a bone regeneration site and prevent the migration of gingival connective tissue and / or peripheral epithelium through the defective area during periodontal surgical procedures have come to the fore. In this report, we have developed a nanoparticle bearing thermosensitive in situ gel formulation of Pluronic F127 and poly(D,L-lactic acid) based membrane to reveal their utilization at GBR by in-vivo applications. In addition, the encouragement of the bone formation in defect area via inhibition of osteoclastic activity is intended by fabrication these biodegradable biomaterials at a lowered Zoledronic Acid (ZA) dose. Both of the developed materials remained stable under specified stability conditions (25 °C, 6 months) and provided the extended release profile of ZA. The in-vivo efficacy of nanoparticle bearing in situ gel formulation, membrane formulation and simultaneous application for guided bone regeneration was investigated in New Zealand female rabbits with a critical size defect of 0.5 × 0.5 cm in the tibia bone for eight weeks. Based on the histopathological findings, lamellar bone and primarily woven bone formations were observed after 8 weeks of post-implantation of both formulations, while fibrosis was detected only in the untreated group. Lamellar bone growth was remarkably achieved just four weeks after the simultaneous application of formulations. Consequently, the simultaneous application of ZA-membrane and ZA-nanoparticles loaded in-situ gel formulations offers enhanced and faster GBR therapy alternatives.

Intranasal versus intraperitoneal Myrj 59-stabilized cubosomes: A potential armamentarium of effective anti-diabetic therapy

The present study is concerned with the suitability of using Myrj 59, out-performing the commonly used stabilizer i.e., poloxamer, for preparation of cubosomes on one hand and gives an insight into the need for distinctive choice of delivery system and administration route towards better diabetes pharmacotherapy on the other hand. In light, repaglinide (REP) cubosomal dispersion and in-situ gel forms were prepared and physicochemically characterized. The selected cubosomal forms were tested for in-vitro drug release and administered via intranasal (IN) and intraperitoneal (IP) routes and compared with Intravenous (IV) REP solution regarding in-vivo antidiabetic efficacy. The results confirmed the formation of cubic nanostructures (170-233 nm), entrapping high REP amounts (93.2-95.66 %). Sustained REP release from selected cubosomal forms was realized with no burst release. Upon in-vivo assessment, IN and IP REP cubosomes and cubosomal gel exhibited superior long-acting in-vivo traits over IV REP solution, respecting percentages of maximum reduction, total decrease in BG levels, and the pharmacological availability. Moreover, IP REP cubosomes and cubosomal gel revealed higher values of the aforementioned parameters than IN counterparts. In conclusion, IN and IP administration of the newly developed cubosomal forms could proffer feasible options for an optimal control of BG levels.

Development of Carbamazepine Nanostructured Lipid Carrier Loaded Thermosensitive Gel for Intranasal Delivery

Purpose: The present research work was designed to formulate and evaluate carbamazepine (CBZ) loaded nanostructured lipid carrier (NLC) based in-situ gel for nasal delivery. Methods: The NLC formulation of CBZ was prepared by microemulsion technique followed by probe sonication and evaluated for particle size, zeta potential, entrapment efficiency and in vitro drug diffusion. NLC formulation was incorporated into in-situ gelling formulation using poloxamer 407 (P407), poloxamer 188 (P188) and mucoadhesive polymer. The effect of concentration of poloxamer 188 (X₁ ), type of mucoadhesive polymer (X₂ ) and concentration of mucoadhesive polymer (X₃ ) on gelling temperature (Y₁ ) and drug diffusion after 8 h (Y₂ ) was studied using Box-Behnken design. In vivo anticonvulsant activity of optimized formulation was studied in Wistar rats by maximal electro-convulsion model (MES). Results: The optimized CBZ NLC formulation, with 20% drug loading, 0.5:1 as Precirol:Capmul MCM ratio as lipid phase and 1:3 as Lipid:Smix ratio, resulted in 89.73±0.2% drug entrapment, 55.95±1.09% of drug diffusion after 8 h, particle size of 132.8 nm with polydispersity index of 0.302 and zeta potential of -29.2±6.1 mV. The in-situ gel formulation with 20% P407, 5% P188 and 0.2% chitosan was optimized and demonstrated excellent gelling ability, gelling temperature in the range of 30 to 35°C, 42.46% of drug diffusion in 8 h by Fickian diffusion mechanism and 31.34±0.76% of drug permeation through sheep nasal mucosa. In vitro anticonvulsant activity in MES model in rat demonstrated significant efficacy (71.95% protection against seizure in extension phase) as compared to plain in-situ nasal gel (50.26% protection against seizure in extension phase). Conclusion: NLC based in-situ gelling formulation demonstrated its potential for nasal delivery of CBZ with improved anticonvulsant activity.

Comparison of three in-situ gels composed of different oil types

A phospholipid-based phase separation in-situ gel (PPSG) system, which consists of phospholipids, medium chain oil (triglyceride) and ethanol as basic ingredients, has been previously developed in our lab. In addition, glycerol monooleate (monoglyceride) and glycerol dioleate (diglyceride) were also reported to be able to form liquid crystal gels. Monoglyceride, diglyceride and triglyceride have different degrees of hydroxyl substitution in glycerol and therefore different amphiphilic properties, which may cause different properties of gels composed of them. In this experiment, glycerol monooleate (GMO), glycerol dioleate (GDO) and glycerol trioleate (GTO) were selected to prepare three kinds of PPSGs. We systematically studied their in-vitro and in-vivo physicochemical properties and investigated their drug release behavior with octreotide (OCT) as the model drug. The results showed that PPSG composed of GTO (GTO-gel) had a different microstructure, a slower solvent diffusion speed and the less irritation to skin. In addition, the drug release result showed that the GTO-gel group had a lower initial release rate and a more stable release profile. All results above indicated that GTO-gel had a greater potential as a drug delivery system.

Development of Moxifloxacin Hydrochloride loaded in-situ gel for the treatment of periodontitis: In-vitro drug release study and antibacterial activity

Periodontitis is one of the most widespread oral diseases. Medicated in-situ gels of Moxifloxacin Hydrochloride for extended period of retention in infected cavity were prepared for improved local action for the treatment of periodontitis. Medicated formulations were prepared using temperature sensitive (poloxamer 407), ion sensitive (gellan gum) and pH sensitive (carbopol 934P) polymers. 32 Full Factorial Design has been applied and prepared batches were characterized by FTIR, pH, syringeability, drug content, clarity, gelation temperature, gelling time, in-vitro gelling capacity, in-vitro diffusion study. Gelation temperature, (in-vitro) gelling time and the nature of gel formed in simulated saliva showed polymeric concentration dependency. Diffusion study of in-situ gel had been performed which showed augmented arrival of medication from 7-12 hours and the discharge was dependent on polymer utilized. The best fitted model was zero order kinetics which indicated that the formulation gave controlled delivery. All preparations were non-Newtonian and display pseudoplastic conduct. Invitro Antimicrobial study was carried out by utilizing E. coli and S. aureus. Optimized formulation containing 19.072 %w/v poloxamer 407 and 0.245 %w/v gellan gum exhibited desired characteristics for developing periodontal drug delivery systems.

Research progress of in-situ gelling ophthalmic drug delivery system

Blindness and vision impairment are the most devastating global health problems resulting in a substantial economic and social burden. Delivery of drug to particular parts of the anterior or posterior segment has been a major challenge due to various protective barriers and elimination mechanisms associated with the unique anatomical and physiological nature of the ocular system. Drug administration to the eye by conventional delivery systems results in poor ocular bioavailability (<5%). The designing of a novel approach for a safe, simple, and effective ocular drug delivery is a major concern and requires innovative strategies to combat the problem. Over the past decades, several novel approaches involving different strategies have been developed to improve the ocular delivery system. Among these, the ophthalmic in-situ gel has attained a great attention over the past few years. This review discussed and summarized the recent and the promising research progress of in-situ gelling in ocular drug delivery system.

Multiparticulate based thermosensitive intra-pocket forming implants for better treatment of bacterial infections in periodontitis

Considering alarming projections in the prevalence of periodontitis, following study was undertaken to develop chitosan-vanillin crosslinked microspheres loaded in-situ gel (MLIG) implants containing ornidazole and doxycycline hyclate for the treatment of pocket infections. Firstly, microspheres were formulated and optimized using response surface methodology for particle size <50 μm, entrapment efficiency >80%, in-vitro drug release (T_80%) >7 days and acceptable mucoadhesion. Further, MLIG were optimized for gelation temperature of 34-37 °C and viscosity <1000 cps respectively. FTIR, DSC and XRD graphs disclosed compatibility and alterations in crystallinity of drugs. In-vitro dissolution study demonstrated non-Fickian type of drug release mechanism for twelve days. Stability studies ascertained MLIG implants were sterilizable and stable for about 11.29 months on refrigeration. The formulations exhibited significant (p < 0.001) antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Enterococcus faecalis, and were found biocompatible and biodegradable during preclinical studies. Ligature-induced periodontal rat model, corroborated significant growth (p < 0.05) of gingival tissue after two weeks. Clinical trials revealed, intra-pocket administration of MLIG along with SRP provided significant reduction in clinical parameters as compared to SRP alone. Conclusively, antimicrobials incorporated thermosensitive, biodegradable, mucoadhesive and syringeable MLIG implants appeared as better option for the treatment of periodontitis.

Disulfiram thermosensitive in-situ gel based on solid dispersion for cataract

To improve the corneal permeability and water-solubility of disulfiram (DSF), which is an ocular drug for cataract, P188 was selected as a matrix to prepare solid dispersion of DSF (DSF_SD) by hot melt method. The DSF_SD was characterized by DSC, XRD, and IR, and the results suggested that DSF was amorphous in DSF_SD. The DSF_SD was added to borate buffer solution (BBS) contained 20% poloxamer P407 and 1.2% poloxamer P188 to form in-situ gel. In vitro and in vivo experiments revealed that DSF_SD combined with in-situ gel (DSF_SD/in-situ gel) increased the residence time and the amount of DSF penetrated through the corneal. The pharmacodynamics studies exhibited DSF_SD/in-situ gel delayed the development of selenium-induced cataract at some content. These results investigated that DSF_SD/in-situ gel as a drug delivery system can improve DSF ocular permeability.

Novel in-situ gel for intravesical administration of ketorolac

The urinary bladder stores urine until the time of urination. Systemic administration of drugs to treat bladder diseases faces several limitations. Therefore, intravesical drug delivery is a promising alternative route of administration. An in-situ gel is used to form a gel inside the bladder cavity and ensure continuous release of the drug even after urination. The objective of the present study was to optimize an in-situ gel formulation of poloxamer and chitosan for intravesical delivery of ketorolac tromethamine. The gelling temperature of the prepared combinations ranged from 20.67 to 25.8 °C. In-vitro release of KT was sustained for up to 7 h using a poloxamer concentration ranging from 17% to 19% and a chitosan concentration ranging from 1% to 2%. Design-Expert® 10 was used to select the optimized formulation (poloxamer/chitosan 17/1.589% w/w) which significantly (p < 0.05) extended the drug release more than each polymer alone. An ex-vivo study showed the ability of the optimized formulation to sustain drug release after emptying two times to mimic urination. Furthermore, the formed gel adhered to the bladder tissue throughout the time period of the experiment. Intravesical administration of the optimized formulation to rabbits via catheter showed no obstruction of urine flow and continuous release of the drug for 12 h.

Periodontal thermoresponsive, mucoadhesive dual antimicrobial loaded in-situ gel for the treatment of periodontal disease: Preparation, in-vitro characterization and antimicrobial study

Background

This study aimed to formulate and characterize in-situ gel containing levofloxacin and metronidazole to release drugs in controlled manner for treatment of periodontitis.

Material and Methods

Medicated in-situ gel with levofloxacin (10% w/v), metronidazole (25% w/v) and vehicle in-situ gel without drugs having poloxamer 407 (20% w/v) and chitosan (0.5%, 1%, 1.5%, 2.0% 2.5% w/v) were prepared and characterized for physicochemical, mechanical properties, stability and in-vitro drug release. Fourier transform infrared spectroscopy and differential scanning calorimetery studies were done. Optimized formulation was evaluated by scanning electron microscope (SEM) and in-vitro antimicrobial activity against 5 bacterial strains.

Results

The results revealed that drugs and polymers were compatible to formulate. All formulations were light yellow, clear and syringeable except formulation having 2.5% w/v chitosan. pH was in the range of 6.20 to 6.74. 1.0% w/v and 1.5% w/v chitosan formulations showed gelation temperature 37 ± 0.32 °C and 34 ± 0.21 °C. Further, mucoadhesive strength indicated mucoadhesivity of gel. In-vitro release study of 1.5% w/v chitosan formulation showed initial burst where about 55-60% MZ and 60-70% LVF got released within 6-7 hrs followed by sustained release upto 48 hrs. SEM images of 1.5% w/v chitosan optimized medicated in-situ and vehicle in-situ gel appeared similar indicating homogeneous mixing of polymers with drugs. In-vitro antimicrobial study showed that medicated in-situ gel was more effective than vehicle.

Conclusions

In conclusion, optimized 1.5% w/v chitosan in-situ gel was thermoresponsive, mucoadhesive, syringeable, and released drugs in slow and controlled manner with effectiveness against broad range of microbes.

Study of thermo-sensitive in-situ gels for ocular delivery

The aim of the present study was the development of thermo-sensitive in-situ gels for in-vitro evaluation of ophthalmic delivery systems of ketorolac tromethamine (KT), based on methylcellulose (MC) in combination with hydroxypropylmethyl cellulose (HPMC). The gel temperature of 1% MC solution was observed at 60°C. It was found that 6% oral rehydration salt without dextrose (ORS) was capable to reduce the gel temperature below physiological temperature. HPMC was added to increase viscosity and drug release time. The results indicated a large increase in viscosity at 37°C with addition of HPMC whch provided sustained release of the drug over a 4h period. From in-vitro release studies, it could be concluded that the developed systems were thus a better alternative to conventional eye drops.