Users Online: 589 | Home Print this page Email this page
Home About us Editorial board Search Ahead of print Current issue Archives Submit article Instructions Subscribe Contacts Login 

 Table of Contents  
Year : 2017  |  Volume : 7  |  Issue : 2  |  Page : 101-106

Thermoreversible in situ gel for subgingival delivery of simvastatin for treatment of periodontal disease

1 Department of Periodontology, Faculty of Dental Sciences, Sri Ramachandra University, Chennai, Tamil Nadu, India
2 Department of Pharmaceutics, Faculty of Pharmacy, Sri Ramachandra University, Chennai, Tamil Nadu, India

Date of Web Publication24-Jul-2017

Correspondence Address:
Suresh Ranga Rao
Department of Periodontology, Faculty of Dental Sciences, Sri Ramachandra University, No. 1 Ramachandra Nagar, Porur, Chennai - 600 116, Tamil Nadu
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jphi.JPHI_26_17

Rights and Permissions

Objective: The aim of this in vitro study was to formulate an in situ thermoreversible injectable gel with poloxamer (PM) and methylcellulose (MC) to deliver simvastatin (SMV) in a controlled manner.
Subjects and Methods: Preformulation studies (Fourier transform infrared and differential scanning calorimetry) to assess the interaction between SMV and MC and PM were performed before gel formulation. Keeping the concentration of SMV at 2.2%, the concentration of PM and MC was altered to formulate in situ thermosensitive gel at 37°C. Rheological studies were carried to analyze the physical property of the various formulations. Drug release profile and stability studies were done for the selected formulation. The in vitro drug release profile was carried out for using open end tube method and ultraviolet spectroscopy.
Results: The preformulation studies showed that there is no interaction between the polymer and drug based on the rheological studies of different formulation, the formulation. F8 gels at 37°C and attains a viscosity of 4150 cps.
Conclusions: PM 25% and MC 5% formed an ideal thermosensitive injectable gel at 37°C for subgingival delivery of SMV and also show controlled drug release for the period of 10 days in vitro.

Keywords: In situ gel, periodontitis, simvastatin

How to cite this article:
Rajendran S, Kumar K S, Ramesh S, Rao SR. Thermoreversible in situ gel for subgingival delivery of simvastatin for treatment of periodontal disease. Int J Pharma Investig 2017;7:101-6

How to cite this URL:
Rajendran S, Kumar K S, Ramesh S, Rao SR. Thermoreversible in situ gel for subgingival delivery of simvastatin for treatment of periodontal disease. Int J Pharma Investig [serial online] 2017 [cited 2018 Aug 20];7:101-6. Available from:

  Introduction Top

Periodontal diseases are a group of inflammatory conditions affecting the supporting structures of the teeth characterized by destruction of periodontal hard and soft tissues resulting in pocket formation, mobility, and in turn leading to tooth loss.[1] The deepened gingival sulcus serves as an ideal environment for the growth and proliferation of periodontopathic bacteria leading to periodontitis.[2] The host immune and inflammatory response is activated by the components of host immune system in a sequential manner. The immune response aims to protect the host tissue from bacterial aggression, but it also acts as a mediator of the periodontal destruction.[3] Apart from bacterial degradation of host tissues directly, Birkedal-Hansen suggest that the host plays a major role in the degradation of host connective tissue.[4] Current periodontal treatment strategies target the bacterial deposits on the tooth surface by mechanical debridement which aids in shifting the pathogenic microflora to a healthier environment.[5] To maintain the balance between tissue destruction and inhibition, treatment strategy was focused on the modulation of host. Simvastatin (SMV), a potent prodrug of hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, belongs to the statin family that blocks conversion of HMG-CoA to mevalonic acid, which is needed for cholesterol biosynthesis, used in the treatment of hyperlipidemia.[6] It had been proved that SMV has additional properties such as anti-inflammatory,[7] bone regenerative,[8] and promotion of new blood vessels.[9] Hence, SMV could be used in the treatment of periodontitis by modulating the host response and control inflammation, thus maintaining homeostasis. The local drug delivery systems use biodegradable polymers that can deliver and achieve a sustained release of the drug over days to combat the periodontal bacteria in the pocket.[10] The advantage of using such a system is the self-elimination of carrier medium. The periodontal pocket which is the target site for local drug delivery is a complex region where there is constant the flow of crevicular fluid. An injectable in situ sustained release gel would be an ideal option for the drug to reach the complex environment and deliver its desired effects. Hydroxypropyl methylcellulose (HPMC) and methylcellulose (MC) are nonionic cellulose ethers used in the topical application of oral sustained release drug delivery system.[11],[12] Poloxamers (PMs) are nonionic, polyoxyethylene-polyoxypropylene-polyoxyethylene (PEO-PPO-PEO) triblock copolymers. Their amphiphilic nature depends on the concentration and temperature.[13],[14],[15] The ability of these hydrogels to carry a significant amount of a drug, and biodegradable, nontoxic, and stable characteristics made them suitable to use as controlled release agents.[16] Lower concentrations of PMs with polymers such as collagen, MC, and HPMC have been used in the formulation of thermosensitive ocular gels.[17] At a lower concentration between 20% and 30% and lower temperatures (4°C–5°C), PM 407 (P407) or Pluronic F 127 remains liquid and turns into gel at particular temperature, this gel can be reversed to liquid when the temperature is lowered and again to gel at room temperature.[18] This thermoreversible gelation property of P407 (18%–35%) has been used as drug delivery system for nasal application.[19],[20],[21] Hence, MC and PMs can be combined to achieve a thermosensitive in situ gel for controlled drug release. The aim of thisin vitro study was to formulate an in situ thermoreversible injectable gel with PM and MC to deliver SMV in a controlled manner.

  Subjects and Methods Top

This in vitro study was conducted in Department of Pharmaceuticals, Faculty of Pharmacy, Sri Ramachandra University. MC 4000 cps was purchased from Central Drug House, New Delhi. SMV was purchased from Microlabs, Mumbai. PM was purchased from Sigma Aldrich, Mumbai. All the chemicals used were analytical grade. Preformulation studies (Fourier transform infrared [FT-IR] and differential scanning calorimetry [DSC]) to assess the interaction between SMV and MC and PM were performed before gel formulation.

Differential scanning calorimetry

Thermal characterization of pure drug and physical mixture was performed with DSC. Samples were weighed (2.00 ± 0.5 mg) and placed in sealed aluminum pans. The samples were scanned at 20°C/min from 25°C to 300°C.

Fourier transform infrared

The interaction between drug and the polymer was assessed using FT-IR (Shimadzu FT-IR 8400S, Japan). A physical mixture (5 g) of each polymer and drug was taken in a ratio of 1:1 and mixed properly with 100 mg of KBr. Pellets were made from the mixture by taking 50 g of the mixture and compressing using a hydraulic press at 15 tonnes pressure. The prepared pellets were scanned from 4000 to 400 cm−1 using FT-IR spectrophotometer.

Hydrolysis of simvastatin

SMV powder was converted to the active SMV hydroxyl acid by dissolving weighed amount of SMV powder in 95% ethanol and 0.1M NaOH and heated at 50°C for 2 h and then the pH was adjusted to 7.4 by adding 0.1M HCl and stored at −20°C.[22],[23]

Formulation of simvastatin gel

A total of 13 different formulations were developed with varying concentration of MC and PM keeping the SMV as constant (2.2%). In brief, the desired concentration of PM was dissolved in 10 ml of cold water by continuous stirring until the polymer is completely dissolved and stored at 4°C. MC and SMV were prepared in the same manner. From this, different concentrations of formulations were prepared [Table 1]. The polymers were stirred continuously with a mechanical stirrer until a homogeneous mixture was achieved. All the formulations were stored in 4°C overnight.
Table 1: Formulation Details

Click here to view


The rheological analysis was performed using a stress- and strain-controlled rheometer model (RHEOPLUS MCR301). Flow measurements were performed with single gap cylinder CC27 geometry, the diameter of rheometer plate and interplate was 20.05 and 0.052 mm, respectively, whereas the cone angle was 1°, max shear rate was 10,000 1/s, and max shear stress was 22,260 Pa. To evaluate the exact gelling temperature, change in the loss modulus and storage modulus was observed in response to gradual change in temperature from 4°C to 40°C.


The complex viscosity and the viscosity in relation to shear rate were also observed from the rheological studies.

Stability studies

Stability testing for 3 months as per the International Conference on Harmonisation norms at a temperature of 40°C ± 2°C was performed. At various time intervals, drug content and pH were analyzed.[24]

In vitro drug release studies

Drug release for selected formulation alone was done using an open end tube method as described in our previous study.[24] Briefly measured quantity of a gel is placed in the open end tube, using phosphate buffered saline of pH 7.4 as the medium at temperature 37°C. Samples were withdrawn at frequent intervals and assessed in ultraviolet spectrometer.

  Results Top

Fourier transform infrared spectroscopy

FTIR analysis revealed that the functional groups of the MC, PM, and SMV remained unaltered when SMV and MC and PM were mixed and assessed [Figure 1].
Figure 1: Fourier transform infrared spectroscopy analysis

Click here to view

Differential scanning calorimetry

In thermal characteristic study, it was observed that the melting point of PM started at 46.2°C and ends at 62.7°C with the peak at 56.9°C. When the physical mixture of PM, MC, and SMV exposed to highest temperature (200°C), the individual meeting point of each component remained unchanged [Figure 2].
Figure 2: Differential scanning calorimetry

Click here to view


All the formulations were semisolid to liquid in consistency, at a minimum temperature of 4°C. Whereas upon warming the formulation turned to liquid and to gel, few formulations attained gelation from their semisolid state. All the different formulation attained different gelation temperature. The storage modulus G [Figure 3]a, “the loss modulus G,” and the complex viscosity (H×) are shown in [Figure 4]a and [Figure 4]b. The temperature at which g0 suddenly varied corresponded to the temperature of the sol-gel transition of F8 [Figure 3]b was observed. The viscosity decreased as the shear rate increased [Figure 4]c.
Figure 3: Rheology study

Click here to view
Figure 4: Viscosity and drug release profile

Click here to view

Drug release study

The drug release profile was controlled release of formulation F8 and was in a controlled manner for a period of 10 days. The release pattern is shown in [Figure 4]d.

Stability study

The stability of the in situ gel for the formulation F8 was assessed at 0, 1, 3, and 6 months' postformulation. The drug content was 99.2% ± 0.06% at baseline, 99.1% ± 0.15% at 1 month, 98.5 ± 0.17 at 3 months, and 98.1 ± 0.17 at 6 months. No change was observed in the pH due to storage; however, change in the drug content was elicited as storage time increased. The appearance of the gel remained clear throughout the observation period [Table 2].
Table 2: Stability Study

Click here to view

  Discussion Top

SMV-based gel has been formulated using MC in different concentrations and its efficacy has been widely studied in vivo.[24],[25] Different concentrations of SMV, namely, 1.2%, 1.7%, and 2.2% have been used to formulate injectable gel using 4% MC.[25],[26] In our previous study, we evaluated 4%, 5%, and 6% MC and 1.2%, 1.7%, and 2.2% SMV gelin vitro and found that 6% MC and 2.2% SMV had a controlled release for a longer period compared to 4% and 5%.[27] Hence, for this study, 2.2% SMV was chosen. Furthermore, the results indicated that the release of the drug in a controlled manner is directly proportional to the concentration of the MC. Although 6% MC gave higher rate of controlled release, its effect on the thermoreversible gelation property of PM has to be evaluated. Hence, to achieve optimum gelling property close to body temperature, three concentrations of MC (4%, 5%, and 6%) and five concentrations of PM (10%, 20%, 25%, 35%, and 30%) were chosen. The physical mixture of MC, PM, and SMV was assessed using DSC and IR, and the results revealed that there was no drug and polymer interaction. The rheology study of formulation F1 and F2 showed that the concentration of PM decreases from 35% to 30% and the gelation temperature increases (11.8°C-F2–14.8°C-F1). F4 attained gelation at 13.3°C, which was less than F1. This could be attributed to the higher viscosity in F4 (5% MC) which had decreased the gelation temperature. Further, the gelation of F7 was at 25.3°C and F8 at 35.8°C, which is closer to the body temperature. Although F9 starts gelation 26.6°C and completes gelation 35.8°C beyond this temperature, it loses its storage modulus. Further to increase the gel strength F9, F10 was formulated with 6% MC. This resulted in higher storage modulus at 10°C and it reduced as the temperature increased close to 25°C. Although F10 exhibited high gel strength, it failed to form in situ gel at body temperature. At lower temperature, water serves as good solvent for PEO and PPO units of P407. The hydrophobic portion of PM is kept separated by the hydrogen bonding between water and PPO chain at lower temperature. When the temperature is high, these hydrogen bonds are disrupted lead to hydrophobic interaction and gel formation. Thus, gelling properties of PM are dependent on proportion of hydrophobic portion.[21] This could be the one of the reasons for gel formation at lower temperature in F1, F2, and F3 where the availability of hydrogen bonds was more as the concentration of MC was only 4% compared to F8. Comparing F10 with F13, we found that in the absence of PM, the MC gel decreased its viscosity as the temperature increases. Both the storage and loss modulus are higher in the presence of PM. The storage modulus being higher than loss modulus. The complex viscosity of all the formulations increased as the temperature increases and it reached the peak along with the storage modulus. In F7, F8, F9, and F10 formulation, the complex viscosity remained stable after gelation till the temperature reached 40°C. Among these four formulations, only F8 had the highest viscosity of 2140 cps whereas F1, F2, and F4 showed higher viscosity than F8 and F1 being the highest of 4150 cps at 37°C. This could possibly be due to overall higher polymer percentage. All the formulations demonstrated shear thinning as the shear rate increased. The high viscosities of the gel at low shear rates would aid in maintaining a good contact between the tooth surface and gingiva, and this will leads to uniform distribution of the gel into the pocket. This property is similar to the shear rate and viscosity of in situ ocular gel.[28]

The storage modulus and loss modulus of F8 formulation till 17.8°C were almost at the same level. From 19.3°C to 31.3°C, the loss modulus was higher which makes the gel less viscous and increases the flowability as well as helps in better handling at room temperature [Figure 3]b.

In vitro drug release of F8 and F12 formulation showed a control drug release. Compared to F12, the rate of drug release was faster in the F8 and after 240 h the percentage of drug release reduced whereas F12 started to reduce only after 288 h. This shows the presence of P407 which increases the percentage of drug release from the gel and MC which can promote sustained release. The results of our study are in accordance with study performed by Desai and Blanchard[29] where the authors showed addition of polyethylene glycol (PEG) or polyvinylpyrrolidone. PEG/poly(lactic-co-glycolic acid) block copolymers accelerated pilocarpine release while the addition of MC slowed the release rate. This indicates that PM alone cannot be used for sustained release system of any drug. Hence, combining both these polymers would lead to sustained release in an in situ gel formulation.

Based on the gel strength, the gelling temperature and release profile of F8 formulation formed the ideal gel for thermosensitive controlled release gel. Further, the gel strength could be enhanced by addition of high viscosity polymers and additives. Although injectable SMV has been used in pilot study in the management of periodontal defect and alveolar ridges,[30] an in situ gel system for delivery of SMV into periodontal pockets could prove to be clinically effective.

  Conclusions Top

PM 25% and MC 5% formed an ideal thermosensitive injectable gel for subgingival delivery of SMV. However, studies have to be carried out to assess whether addition of another polymer like Carbopol can increase the gel strength after gelation which could help the gel to reach the subgingival region for the longest period.


The authors would like to thank the Indian Council of Medical Research (ICMR) for their support as this work is a part of a PhD program supported by ICMR, New Delhi, India. The authors would also like to thank the Central Research Facility of Sri Ramachandra University, Chennai, India, for providing support to use their facility.

Financial support and sponsorship

This study was financially supported by the Indian Council of Medical Research.

Conflicts of interest

There are no conflicts of interest.

  References Top

Socransky SS, Haffajee AD. The bacterial etiology of destructive periodontal disease: Current concepts. J Periodontol 1992;63:322-31.  Back to cited text no. 1
Carranza F, editor. The periodontal pocket. In: Glickman's Clinical Periodontology. Philadelphia: W.B. Saunders Co.; 1984. p. 201-25.  Back to cited text no. 2
Bascones-Martínez A, Figuero-Ruiz E. Periodontal diseases as bacterial infection. Med Oral Patol Oral Cir Bucal 2004;9 Suppl:101-7, 92-100.  Back to cited text no. 3
Birkedal-Hansen H. Role of cytokines and inflammatory mediators in tissue destruction. J Periodontal Res 1993;28(6 Pt 2):500-10.  Back to cited text no. 4
Listgarten MA, Loomer PM. Microbial identification in the management of periodontal diseases. A systematic review. Ann Periodontol 2003;8:182-92.  Back to cited text no. 5
Sugiyama M, Kodama T, Konishi K, Abe K, Asami S, Oikawa S. Compactin and simvastatin, but not pravastatin, induce bone morphogenetic protein-2 in human osteosarcoma cells. Biochem Biophys Res Commun 2000;271:688-92.  Back to cited text no. 6
Davignon J, Laaksonen R. Low-density lipoprotein-independent effects of statins. Curr Opin Lipidol 1999;10:543-59.  Back to cited text no. 7
Mundy G, Garrett R, Harris S, Chan J, Chen D, Rossini G, et al. Stimulation of bone formationin vitro and in rodents by statins. Science 1999;286:1946-9.  Back to cited text no. 8
Kureishi Y, Luo Z, Shiojima I, Bialik A, Fulton D, Lefer DJ, et al. The HMG-CoA reductase inhibitor simvastatin activates the protein kinase Akt and promotes angiogenesis in normocholesterolemic animals. Nat Med 2000;6:1004-10.  Back to cited text no. 9
Jeyanthi R, Akiyama A, Roberts FD, Van Hamont J, Friden P. One-month Controlled Release of an Antimicrobial Peptide from Biodegreaable Poly (Lactide/Glycolide) Microspheres for the Treatment of Periodontitis, Proceedings International Symposium Controlled Release Bioact Mater; 1997. p. 883-4.  Back to cited text no. 10
Golub LM, Kleinberg I. Gingival crevicular fluid: A new diagnostic aid in managing the periodontal patient. Oral Sci Rev 1976;(8):49-61.  Back to cited text no. 11
Itoh K, Hatakeyama T, Shimoyama T, Miyazaki S, D'Emanuele A, Attwood D. In situ gelling formulation based on methylcellulose/pectin system for oral-sustained drug delivery to dysphagic patients. Drug Dev Ind Pharm 2011;37:790-7.  Back to cited text no. 12
Rajabi-Siahboomi AR, Jordan MP. Slow release HPMC matrix systems. Eur Pharm Rev 2000;5:21-3.  Back to cited text no. 13
Miller SC, Drabic BR. Rheological properties of poloxamer vehicles. Int J Pharm 1984;18:269-76.  Back to cited text no. 14
Vadnere M, Amidon G, Lindenbaum S, Haslam JL. Thermodynamic studies on the gel-sol transition of some pluronic polyols. Int J Pharm 1984;22:207-18.  Back to cited text no. 15
Gilbert JC, Washington C, Davies MC, Hadgraft J. The behaviour of pluronic F127 in aqueous solution studies using fluorescent probes. Int J Pharm 1987;40:93.  Back to cited text no. 16
Singh-Joy SD, McLain VC. Safety assessment of poloxamers 101, 105, 108, 122, 123, 124, 181, 182, 183, 184, 185, 188, 212, 215, 217, 231, 234, 235, 237, 238, 282, 284, 288, 331, 333, 334, 335, 338, 401, 402, 403, and 407, poloxamer 105 benzoate, and poloxamer 182 dibenzoate as used in cosmetics. Int J Toxicol 2008;27 Suppl 2:93-128.  Back to cited text no. 17
Mansour M, Mansour S, Mortada ND, Abd Elhady SS. Ocular poloxamer-based ciprofloxacin hydrochloride in situ forming gels. Drug Dev Ind Pharm 2008;34:744-52.  Back to cited text no. 18
Escobar-Chávez JJ, López-Cervantes M, Naïk A, Kalia YN, Quintanar-Guerrero D, Ganem-Quintanar A. Applications of thermo-reversible pluronic F-127 gels in pharmaceutical formulations. J Pharm Pharm Sci 2006;9:339-58.  Back to cited text no. 19
Pisal SS, Reddy P, Paradkar AR, Mahadik KR, Kadam SS. Nasal melatonin gels using Pluronic PF 127 for chronobiological treatment of sleep disorder. Indian J Biotechnol 2004;3:369-77.  Back to cited text no. 20
Patel M, Thakkar H, Kasture PV. Preparation and evaluation of thermoreversible formulations of hydrochloride for nasal drug delivery. J Pharm Res 2007;6:89-93.  Back to cited text no. 21
Mahajan HS, Shah SK, Surana SJ. Nasal in situ gel containing hydroxypropyl β-cyclodextrin inclusion complex of artemether: Development andin vitro evaluation. J Incl Phenom Macrocycl Chem 2011;70:49-58.  Back to cited text no. 22
Jeon JH, Thomas MV, Puleo DA. Bioerodible devices for intermittent release of simvastatin acid. Int J Pharm 2007;340:6-12.  Back to cited text no. 23
ICH Harmonized Tripartite Guidelines. Stability Testing of New Drug Substances and Products. ICH Committee; 2003. p. 8.  Back to cited text no. 24
Thylin MR, McConnell JC, Schmid MJ, Reckling RR, Ojha J, Bhattacharyya I, et al. Effects of simvastatin gels on murine calvarial bone. J Periodontol 2002;73:1141-8.  Back to cited text no. 25
Pradeep AR, Thorat MS. Clinical effect of subgingivally delivered simvastatin in the treatment of patients with chronic periodontitis: A randomized clinical trial. J Periodontol 2010;81:214-22.  Back to cited text no. 26
Rajendran S, Ramesh S, Kumar S, Rao SR.In vitro release kinetics of simvastatin from methyl cellulose gel. Int J Pharm Pharm Sci 2015;7:106-10.  Back to cited text no. 27
Sampathi S. Design, development and characterization: In situ gels of lomefloxacin hydrochloride for ocular drug delivery. World J Pharm Pharm Sci 2014;3:2350-64.  Back to cited text no. 28
Desai SD, Blanchard J.In vitro evaluation of pluronic copoly(Oxyethylene/Oxybutylene) E B: A study of phase PF-127 based controlled release ocular delivery systems for 41 8 behavior, Macromolecules 30 (1997) 1347 pilocarpine. J Pharm Sci 1998;87:226-30.  Back to cited text no. 29
Tariq M, Iqbal Z, Ali J, Baboota S, Talegaonkar S, Ahmad Z, et al. Treatment modalities and evaluation models for periodontitis. Int J Pharm Investig 2012;2:106-22.  Back to cited text no. 30


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2]


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this article
Subjects and Methods
Article Figures
Article Tables

 Article Access Statistics
    PDF Downloaded138    
    Comments [Add]    

Recommend this journal