Gastroretentive drug delivery system of acyclovir-loaded alginate mucoadhesive microspheres: formulation and evaluation

Advanced polymers and recent advancements on gastroretentive drug delivery system; a comprehensive review

Oral route of drug administration is typically the initial option for drug administration because it is both practical and affordable. However, major drawback of this route includes the release of drug at a specified place thus reduces the bioavailability. This could be overcome by utilising the gastroretentive drug delivery system (GRRDS). Prolonged stomach retention improves bioavailability and increases solubility for medicines that are unable to dissolve in high pH environments. Many recent advancements in the floating, bio adhesive, magnetic, expandable, raft forming and ion exchange systems have been made that had led towards advanced form of drug delivery. From the past few years, floating drug delivery system has been most commonly utilised for the delivery of drug in a delayed manner. Various polymers have been utilised for manufacturing of these systems, including alginates, chitosan, pectin, carrageenan's, xanthan gum, hydroxypropyl cellulose, carbomer, polyethylene oxide and sodium carboxy methyl cellulose. Chitosan, pectin and xanthan gum have been found to be most commonly used polymers in the manufacturing of drug inclusion complex for gastroretentive drug delivery. This study aimed to define various types and advanced polymers as well as also highlights recent advances and future perspectives of gastroretentive drug delivery system.

Spray-Dried Mucoadhesive Re-dispersible Gargle of Chlorhexidine for Improved Response Against Throat Infection: Formulation Development, In Vitro and In Vivo Evaluation

Drug delivery to the buccal mucosa is one of the most convenient ways to treat common mouth problems. Here, we propose a spray-dried re-dispersible mucoadhesive controlled release gargle formulation to improve the efficacy of chlorhexidine. The present investigation portrays an approach to get stable and free-flowing spray-dried porous aggregates of chlorhexidine-loaded sodium alginate nanoparticles. The ionic gelation technique aided with the chlorhexidine's positive surface charge-based crosslinking, followed by spray drying of the nanoparticle's dispersion in the presence of lactose- and leucine-yielded nano-aggregates with good flow properties and with a size range of about 120-350 nm. Provided with the high entrapment efficiency (87%), the particles showed sustained drug release behaviors over a duration of 10 h, where 87% of the released drug got permeated within 12 h. The antimicrobial activity of the prepared formulation was tested on S. aureus, provided with a higher zone of growth inhibition than the marketed formulation. Aided with an appropriate mucoadhesive strength, this product exhibited extended retention of nanoparticles in the throat region, as shown by in vivo imaging results. In conclusion, the technology, provided with high drug retention and extended effect, could be a potential candidate for treating several types of throat infections.

Contemporary Aspects of Designing Marine Polysaccharide Microparticles as Drug Carriers for Biomedical Application

The main goal of modern pharmaceutical technology is to create new drug formulations that are safer and more effective. These formulations should allow targeted drug delivery, improved drug stability and bioavailability, fewer side effects, and reduced drug toxicity. One successful approach for achieving these objectives is using polymer microcarriers for drug delivery. They are effective for treating various diseases through different administration routes. When creating pharmaceutical systems, choosing the right drug carrier is crucial. Biomaterials have become increasingly popular over the past few decades due to their lack of toxicity, renewable sources, and affordability. Marine polysaccharides, in particular, have been widely used as substitutes for synthetic polymers in drug carrier applications. Their inherent properties, such as biodegradability and biocompatibility, make marine polysaccharide-based microcarriers a prospective platform for developing drug delivery systems. This review paper explores the principles of microparticle design using marine polysaccharides as drug carriers. By reviewing the current literature, the paper highlights the challenges of formulating polymer microparticles, and proposes various technological solutions. It also outlines future perspectives for developing marine polysaccharides as drug microcarriers.

Development of Lipid-Based Gastroretentive Delivery System for Gentian Extract by Double Emulsion-Melt Dispersion Technique

Gentian (Gentiana lutea L., Gentianaceae) root extract (GRE) is used for the treatment of gastrointestinal disorders. However, its bioactive potential is limited in conventional forms due to the low bioavailability and short elimination half-life of the dominant bioactive compound, gentiopicroside. The aim of study was to encapsulate GRE in the lipid-based gastroretentive delivery system that could provide high yield and encapsulation efficiency, as well as the biphasic release of gentiopicroside from the tablets obtained by direct compression. Solid lipid microparticles (SLM) loaded with GRE were prepared by freeze-drying double (W/O/W) emulsions, which were obtained by a multiple emulsion-melt dispersion technique, with GRE as the inner water phase, Gelucire^® 39/01 or 43/01, as lipid components, with or without the addition of porous silica (Sylysia^® 350) in the outer water phase. Formulated SLM powders were examined by SEM and mercury intrusion porosimetry, as well as by determination of yield, encapsulation efficiency, and flow properties. Furthermore, in vitro dissolution of gentiopicroside, the size of the dispersed systems, mechanical properties, and mucoadhesion of tablets obtained by direct compression were investigated. The results have revealed that SLM with the macroporous structure were formulated, and, consequently, the powders floated immediately in the acidic medium. Formulation with porous silica (Sylysia^® 350) and Gelucire^® 43/01 as a solid lipid was characterized with the high yield end encapsulation efficiency. Furthermore, the mucoadhesive properties of tablets obtained by direct compression of that formulation, as well as the biphasic release of gentiopicroside, presence of nanoassociates in dissolution medium, and optimal mechanical properties indicated that a promising lipid-based gastroretentive system for GRE was developed.

Ambroxol Hydrochloride Loaded Gastro-Retentive Nanosuspension Gels Potentiate Anticancer Activity in Lung Cancer (A549) Cells

This study aimed to develop gastro-retentive sustained-release ambroxol (ABX) nanosuspensions utilizing ambroxol-kappa-carrageenan (ABX-CRG_K) complexation formulations. The complex was characterized by differential scanning calorimetry, powder x-ray diffractometer, and scanning electron microscopy. The prepared co-precipitate complex was used for the development of the sustained-release formulation to overcome the high metabolic and poor solubility problems associated with ABX. Furthermore, the co-precipitate complex was formulated as a suspension in an aqueous floating gel-forming vehicle of sodium alginate with chitosan, which might be beneficial for targeting the stomach as a good absorption site for ABX. The suspension exhibited rapid floating gel behaviour for more than 8 h, thus confirming the gastro-retentive effects. Particle size analysis revealed that the optimum nanosuspension (ABX-NS) had a mean particle size of 332.3 nm. Afterward, the ABX released by the nanoparticles would be distributed to the pulmonary tissue as previously described. Based on extensive pulmonary distribution, the developed nanosuspension-released ABX nanoparticles showed significant cytotoxic enhancement compared to free ABX in A549 lung cancer cells. However, a significant loss of mitochondrial membrane potential (MMP) also occurred. The level of caspase-3 was the highest in the ABX-NS-released particle-treated samples, with a value of 416.6 ± 9.11 pg/mL. Meanwhile, the levels of nuclear factor kappa beta, interleukins 6 and 1 beta, and tumour necrosis alpha (NF-kB, IL-6, IL-1β, and TNF-α, respectively) were lower for ABX-NS compared to free ABX (p < 0.05). In caspase-3, Bax, and p53, levels significantly increased in the presence of ABX-NS compared to free ABX. Overall, ABX-NS produced an enhancement of the anticancer effects of ABX on the A549 cells, and the developed sustained-release gel was successful in providing a gastro-retentive effect.

Synthesis, Characterization and Safety Evaluation of Sericin-Based Hydrogels for Controlled Delivery of Acyclovir

Conventional formulations of antiviral drug acyclovir have various limitations such as low bioavailability. The current study was aimed at developing polymeric matrices for the controlled delivery of acyclovir using sericin as polymer and acrylic acid (AA) as a monomer. The free radical polymerization technique was used for hydrogel formulation. Briefly, sericin was chemically cross-linked with acrylic acid. N′-N′-methylene bis-acrylamide (MBA) and ammonium persulfate (APS) were used as cross-linker and initiator, respectively. FTIR spectra showed that acyclovir was successfully loaded into sericin hydrogel. SEM micrographs revealed that the outer surface was solid-like and smooth. According to DSC thermograms, the developed polymeric network was thermally stable. Amorphous nature of acyclovir was observed in XRD. The pH of medium and reactants’ concentration affected swelling dynamics and acyclovir release pattern. In addition, drug release occurred through a diffusion-controlled process. Sericin hydrogel suspension was well tolerable up to 3800 mg/kg of rabbits’ body weight. Haematology and serum chemistry results were well within the range signifying normal liver and kidney functions. Similarly, histopathology slides of the rabbit’s vital organs were also in normal condition without causing any histopathological change. It was concluded from the findings that sericin-co-AA polymeric matrices are ideal for the pH-dependent delivery of acyclovir.

Central Composite Design for the Development and Evaluation of Floating-mucoadhesive Tablets of Gliclazide

Background:

Gliclazide assimilation rate from the gastrointestinal (GI) tract is slow and inconstant, which may be either due to poor dissolution or poor permeability of the drug across the GI membrane.

Objective:

The present investigation deals with the formulation of floating-mucoadhesive tablets of gliclazide for oral administration using the central composite design by direct compression technique, using HPMC K4M and Carbopol 934 as release controlling polymers and sodium bicarbonate as an effervescent agent.

Methods:

Central composite design was employed to quantify the effect of three factorsconcentration of HPMC K4M (X1), the concentration of Carbopol 934 (X2), and concentration of sodium bicarbonate (X3) on floating lag time, drug release and mucoadhesive time of the formulation.

Results:

The results revealed that floating lag time decreases with a rise in the concentration of sodium bicarbonate, drug release was highest at low levels of HPMC and Carbopol and mucoadhesive time was highest at a high level of Carbopol.

Conclusion:

The optimized batch (F-7) shows a mucoadhesive time of 23 minutes 27 seconds, floating lag time of 22 seconds and in vitro cumulative percentage of drug release 86.73 % in 10h. From the investigation, it can be summarized that the gastro-retentive drug delivery can be utilized to enhance bioavailability and gastric residence time of the drugs.

In-Depth Study into Polymeric Materials in Low-Density Gastroretentive Formulations

The extensive use of oral dosage forms for the treatment of diseases may be linked to deficient pharmacokinetic properties. In some cases the drug is barely soluble; in others, the rapid transit of the formulation through the gastrointestinal tract (GIT) makes it difficult to achieve therapeutic levels in the organism; moreover, some drugs must act locally due to a gastric pathology, but the time they remain in the stomach is short. The use of formulations capable of improving all these parameters, as well as increasing the resident time in the stomach, has been the target of numerous research works, with low-density systems being the most promising and widely explored, however, there is further scope to improve these systems. There are a vast variety of polymeric materials used in low-density gastroretentive systems and a number of methods to improve the bioavailability of the drugs. This works aims to expedite the development of breakthrough approaches by providing an in-depth understanding of the polymeric materials currently used, both natural and synthetic, their properties, advantages, and drawbacks.

Floating Microspheres of Enalapril Maleate as a Developed Controlled Release Dosage Form: Investigation of the Effect of an Ionotropic Gelation Technique

OBJECTIVES

The purpose of this study was to provide a control drug delivery system through a newly approved work to enhance the absorption and bioavailability of enalapril maleate loaded floating microspheres by ionotropic gelation technique using a hydrophilic carrier.

MATERIALS AND METHODS

Eleven developed formulations of floating microspheres were prepared by ionotropic gelation using different concentrations of sodium alginate, iota-carrageenan, sodium bicarbonate, calcium chloride, and the drug. These microspheres were characterized using a diversity of parameters like micrometric properties, percentage yield, entrapment efficiency, in vitro buoyancy, in vitro drug release, and kinetics of drug release. The optimum formula was evaluated and identified for drug-excipients compatibility using fourier transform-infrared spectroscopy (FT-IR), surface morphology, powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC).

RESULTS

From the results, F4 was selected as the optimum formula since it provides a faster and premium release of drug from the matrix (91.4%). Kinetics of drug release was found to depend on both diffusion and erosion mechanisms, as the correlation coefficient (R2) was best fitted with Korsmeyer's model and the release exponent (n) was shown to be between 0.43 and 0.84. Scanning electron microscopy images demonstrated spherical, discrete, and freely flowing microspheres with a particle size of 199.4±0.04 μm. Optimum buoyancy properties, percentage yield, and drug entrapment efficiency were achieved. FT-IR showed no interaction between enalapril and the polymers. DSC and XRD showed the miscibility of the drug with the polymers while maintaining the stable crystalline properties of enalapril loaded in the prepared microspheres.

CONCLUSION

The developed floating microspheres of enalapril maleate can be considered a promising controlled drug delivery system, thereby improving patient compliance.

Applications of alginate microspheres in therapeutics delivery and cell culture: Past, present and future

Polymers are the backbone of pharmaceutical drug delivery. There are several polymers with varying properties available today for use in different pharmaceutical applications. Alginate is widely used in biomedical research due to its attractive features such as biocompatibility, biodegradability, inertness, low cost, and ease of production and formulation. Encapsulation of therapeutic agents in alginate/alginate complex microspheres protects them from environmental stresses, including the acidic environment in the gastro-intestinal tract (GIT) and enzymatic degradation, and allows targeted and sustained delivery of the agents. Microencapsulation is playing an increasingly important role in drug delivery as evidenced by the recent surge in research articles on the use of alginate in the delivery of small molecules, cells, bacteria, proteins, vaccines, and for tissue engineering applications. Formulation of these alginate microspheres (AMS) are commonly achieved by conventional external gelation method using various instrumental manipulation such as vortexing, homogenization, ultrasonication or spray drying, and each method affects the overall particle characteristics. In this review, an inclusive summary of the currently available methods for the formulation of AMS, its recent use in the encapsulation and delivery of therapeutics, and future outlook will be discussed.

Acyclovir chemical kinetics with the discovery and identification of newly reported degradants and degradation pathways involving formaldehyde as a degradant and reactant intermediate

The purpose of this research was to determine acyclovir (ACV) acidic degradation kinetics which is relevant to gastric retentive device product design. A stability-indicating method revealed two unknown degradation products which have been identified by mass spectrometry as ACV and guanine formaldehyde adducts. In addition to the formation of these adducts, a proposed degradation scheme identifies the formation of methyl acetal ethylene glycol, formaldehyde, ethylene glycol, and guanine as additional ACV degradation products. pH-rate profiles were explained by using a rate law which assumed acid-catalyzed hydrolysis of protonated and unprotonated ACV. The predicted and observed rate constants were in good agreement. Data-driven excipient selection recommendations were based on the chemical kinetic study results, degradation scheme, and pH-rate profiles. The average activation energy for the degradation reaction was determined to be 31.3±1.6kcal/mol. The predicted ACV t_90% at 37°C and pH 1.2 was calculated to be 7.2days. As a first approximation, this suggests that ACV gastric retentive devices designed to deliver drug for 7days should have acceptable drug product stability in the stomach.

Acyclovir-Polyethylene Glycol 6000 Binary Dispersions: Mechanistic Insights

The dissolution and subsequent oral bioavailability of acyclovir (ACY) is limited by its poor aqueous solubility. An attempt has been made in this work to provide mechanistic insights into the solubility enhancement and dissolution of ACY by using the water-soluble carrier polyethylene glycol 6000 (PEG6000). Solid dispersions with varying ratios of the drug (ACY) and carrier (PEG6000) were prepared and evaluated by phase solubility, in vitro release studies, kinetic analysis, in situ perfusion, and in vitro permeation studies. Solid state characterization was done by powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) analysis, and surface morphology was assessed by polarizing microscopic image analysis, scanning electron microscopy, atomic force microscopy, and nuclear magnetic resonance analysis. Thermodynamic parameters indicated the solubilization effect of the carrier. The aqueous solubility and dissolution of ACY was found to be higher in all samples. The findings of XRD, DSC, FTIR and NMR analysis confirmed the formation of solid solution, crystallinity reduction, and the absence of interaction between the drug and carrier. SEM and AFM analysis reports ratified the particle size reduction and change in the surface morphology in samples. The permeation coefficient and amount of ACY diffused were higher in samples in comparison to pure ACY. Stability was found to be higher in dispersions. The results suggest that the study findings provided clear mechanical insights into the solubility and dissolution enhancement of ACY in PEG6000, and such findings could lay the platform for resolving the poor aqueous solubility issues in formulation development.

Interactions of mussel-inspired polymeric nanoparticles with gastric mucin: Implications for gastro-retentive drug delivery

Mussel-inspired polydopamine (pD) coatings have several unique characteristics such as durability, versatility, and robustness. In this study, we have designed pD-coated nanoparticles (NPs) of methoxy polyethylene glycol-b-poly(ε-caprolactone) (mPEG-PCL@pD) as prospective nanoscale mucoadhesive platforms for gastro-retentive drug delivery. Successful pD coating on the NPs was confirmed by Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. Mucoadhesion of pD-coated NPs was investigated in vitro using commercially available mucin under stomach lumen-mimetic conditions. Mucin-NP interactions were monitored by dynamic light scattering, which showed a significant change in particle size distribution of pD-coated NPs at mucin/NP ratios of 1:1, 1:2, and 1:4w/w. Turbidity measurements indicated the formation of large mucin-NP aggregates causing a significant increase in turbidity at mucin/NP ratios of 2:1 and 4:1w/w. pD-coated NPs exhibited a significantly higher mucin adsorption ability compared to uncoated NPs at mucin/NP ratios of 1:4, 1:2, and 1:1w/w. Zeta potential measurements demonstrated that mucin-pD-coated NP interactions were not electrostatic in nature. An ex vivo wash-off test conducted using excised sheep stomach revealed that 78% of pD-coated NPs remained attached to the mucosa after 8h of incubation, compared to only 33% of uncoated NPs. In vitro release of rifampicin, used as a model drug, showed a similar controlled release profile from both pD-coated and uncoated NPs. Our results serve to expand the versatility of mussel-inspired coatings to the design of mucoadhesive nanoscale vehicles for oral drug delivery.

Gastroretentive systems - a proposed strategy to modulate anthocyanin release and absorption for the management of diabetes

Several reports have indicated a positive correlation between the consumption of anthocyanins (ACN) and biomarkers relating to the improvement of type 2 diabetes (T2D). However, the results from in vitro studies often do not translate into clinical evidence. Potential causes of these discrepancies are experimental conditions that lack physiological relevancy; extensive degradation of these compounds in vivo due to changes in pH and metabolism; and a short residence time in the absorption window in relation to the absorption rate. Here, gastroretentive systems (GRS) are proposed as a strategy to overcome the limitations in ACN delivery and to reduce the existing bench-to-subject gap. This review summarizes recent literature on the use of ACN for the management and control of T2D, followed by GRS platforms to promote a sustained release of ACN for increased health benefits.

The Interesting Case of Acyclovir Delivered Using Chitosan in Humans: Is it a Drug Issue or Formulation Issue?

PURPOSE

Attempts to formulate acyclovir to improve its bioavailability and reduce the frequency of dosing from the present q4h have not materialized.

DISCUSSION

It was thought that an approach using permeability enhancer such as chitosan may impart improved absorption profile to acyclovir; however, the recently published pharmacokinetic data suggested otherwise. The lack of promise of chitosan formulation was attributed to the muco-adhesive properties of chitosan to hold off acyclovir and preventing its transport across the gastrointestinal tract. However, the above hypothesis was refuted by another published human pharmacokinetic study of fexofenadine formulated with chitosan formulation - in this work it was unambiguously shown that chitosan helped in enhanced absorption of fexofenadine which is a well-known Pgp substrate. If one examines the pharmacokinetic disposition of acyclovir, it is clear that renal elimination is so rapid necessitating frequent dosing of acyclovir. In summary, the ability of chitosan based formulations to aid in the oral absorption of drugs may be drug dependent as enumerated by data obtained from acyclovir and fexofenadine. While chitosan favourably improved the pharmacokinetics of fexofenadine, acyclovir may not be ideal for chitosan type of formulation.

CONCLUSION

The choice of the drug and the formulation type intended to deliver the drug need to be made in a diligent and pragmatic fashion.

Micro- and nanoparticles by electrospray: advances and applications in foods

Micro- and nanotechnology are tools being used strongly in the area of food technology. The electrospray technique is booming because of its importance in developing micro- and nanoparticles containing an active ingredient as bioactive compounds, enhancing molecules of flavors, odors, and packaging coatings, and developing polymers that are obtained from food (proteins, carbohydrates), as chitosan, alginate, gelatin, agar, starch, or gluten. The electrospray technique compared to conventional techniques such as nanoprecipitation, emulsion-diffusion, double-emulsification, and layer by layer provides greater advantages to develop micro- and nanoparticles because it is simple, low cost, uses a low amount of solvents, and products are obtained in one step. This technique could also be applied in the agrifood sector for the preparation of controlled and/or prolonged release systems of fertilizer or agrochemicals, for which more research must be conducted.

Mucoadhesive tablets for controlled release of acyclovir

Mucoadhesive chitosan (CS) and/or hydroxypropyl-methylcellulose (HPMC) tablets for gastric drug delivery of acyclovir (ACV) have been developed in order to improve the ACV oral bioavailability. Swelling, bioadhesive and dissolution studies were carried out in two acidic media (pH 1.5 and 4) in order to determine the tablets behaviour in both fed and fasted states. All the designed tablets showed good mucoadhesive properties on gastric mucosa due to the presence of CS and/or HPMC. In vitro dissolution of ACV from tablets was influenced by the swelling behaviour of each polymer. All data release of the studied tablets fitted to Hopfenberg model, which describes drug release from tablets displaying heterogeneous erosion. HPMC and CS/HPMC tablets revealed a sustained release for 24 h, but a complete dissolution of the tablets was not produced at this time. On the contrary, tablets which contained only CS as polymer were able to release the total amount of ACV for 4 h, due to the CS imbibition and erosion processes in pH 1.5 medium. These results allowed us to conclude that CS is the excipient to be chosen to obtain gastroretentive formulations, due to its demonstrated gastric compatibility.